uu.seUppsala University Publications
Change search
Refine search result
12 1 - 50 of 61
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Andrews, David
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gurnett, D. A.
    Morgan, D.
    Nemec, F.
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Control of the topside Martian ionosphere by crustal magnetic fields2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 4, p. 3042-3058Article in journal (Refereed)
    Abstract [en]

    We present observations from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument onboard Mars Express of the thermal electron plasma density of the Martian ionosphere and investigate the extent to which it is influenced by the presence of Mars's remnant crustal magnetic fields. We use locally measured electron densities, derived when MARSIS is operating in active ionospheric sounding (AIS) mode, covering an altitude range from approximate to 300km to approximate to 1200km. We compare these measured densities to an empirical model of the dayside ionospheric plasma density in this diffusive transport-dominated regime. We show that small spatial-scale departures from the averaged values are strongly correlated with the pattern of the crustal fields. Persistently elevated densities are seen in regions of relatively stronger crustal fields across the whole altitude range. Comparing these results with measurements of the (scalar) magnetic field also obtained by MARSIS/AIS, we characterize the dayside strength of the draped magnetic fields in the same regions. Finally, we provide a revised empirical model of the plasma density in the Martian ionosphere, including parameterizations for both the crustal field-dominated and draping-dominated regimes.

  • 2.
    Andrews, David J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dieval, C.
    Duru, F.
    Gurnett, D. A.
    Morgan, D.
    Witasse, O.
    Oblique reflections in the Mars Express MARSIS data set: Stable density structures in the Martian ionosphere2014In: Journal of Geophysical Research-Space Physics, ISSN 2169-9380, Vol. 119, no 5, p. 3944-3960Article in journal (Refereed)
    Abstract [en]

    The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard the European Space Agency's Mars Express (MEX) spacecraft routinely detects evidence of localized plasma density structures in the Martian dayside ionosphere. Such structures, likely taking the form of spatially extended elevations in the plasma density at a given altitude, give rise to oblique reflections in the Active Ionospheric Sounder data. These structures are likely related to the highly varied Martian crustal magnetic field. In this study we use the polar orbit of MEX to investigate the repeatability of the ionospheric structures producing these anomalous reflections, examining data taken in sequences of multiple orbits which pass over the same regions of the Martian surface under similar solar illuminations, within intervals lasting tens of days. Presenting three such examples, or case studies, we show for the first time that these oblique reflections are often incredibly stable, indicating that the underlying ionospheric structures are reliably reformed in the same locations and with qualitatively similar parameters. The visibility, or lack thereof, of a given oblique reflection on a single orbit can generally be attributed to variations in the crustal field within the ionosphere along the spacecraft trajectory. We show that, within these examples, oblique reflections are generally detected whenever the spacecraft passes over regions of intense near-radial crustal magnetic fields (i.e., with a cusp-like configuration). The apparent stability of these structures is an important feature that must be accounted for in models of their origin.

  • 3.
    Andrews, David J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Barabash, S.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Hall, B. E. S.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Holmström, M.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Lester, M.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Morgan, D. D.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ramstad, R.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Sanchez-Cano, B.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Way, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. NASA Goddard Inst Space Studies, New York, NY USA..
    Witasse, O.
    ESA ESTEC, Noordwijjk, Netherlands..
    Plasma observations during the Mars atmospheric "plume" event of March-April 20122016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 4, p. 3139-3154Article in journal (Refereed)
    Abstract [en]

    We present initial analyses and conclusions from plasma observations made during the reported "Mars plume event" of March-April 2012. During this period, multiple independent amateur observers detected a localized, high-altitude "plume" over the Martian dawn terminator, the cause of which remains to be explained. The estimated brightness of the plume exceeds that expected for auroral emissions, and its projected altitude greatly exceeds that at which clouds are expected to form. We report on in situ measurements of ionospheric plasma density and solar wind parameters throughout this interval made by Mars Express, obtained over the same surface region but at the opposing terminator. Measurements in the ionosphere at the corresponding location frequently show a disturbed structure, though this is not atypical for such regions with intense crustal magnetic fields. We tentatively conclude that the formation and/or transport of this plume to the altitudes where it was observed could be due in part to the result of a large interplanetary coronal mass ejection (ICME) encountering the Martian system. Interestingly, we note that the only similar plume detection in May 1997 may also have been associated with a large ICME impact at Mars.

  • 4.
    Andrews, David J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fraenz, M.
    Dubinin, E.
    Duru, F.
    Morgan, D.
    Witasse, O.
    Determination of local plasma densities with the MARSIS radar: Asymmetries in the high-altitude Martian ionosphere2013In: Journal of Geophysical Research: Space Physics, ISSN 2169-9380, Vol. 118, no 10, p. 6228-6242Article in journal (Refereed)
    Abstract [en]

    We present a novel method for the automatic retrieval of local plasma density measurements from the Mars advanced radar for subsurface and ionospheric sounding (MARSIS) active ionospheric sounder (AIS) instrument. The resulting large data set is then used to study the configuration of the Martian ionosphere at altitudes above approximate to 300km. An empirical calibration routine is used, which relates the local plasma density to the measured intensity of multiple harmonics of the local plasma frequency oscillation, excited in the plasma surrounding the antenna in response to the transmission of ionospheric sounding pulses. Enhanced accuracy is achieved in higherdensity (n(e)>150cm(-3)) plasmas, when MARSIS AIS is able to directly measure the fundamental frequency of the local plasma oscillation. To demonstrate the usefulness of this data set, the derived plasma densities are binned by altitude and solar zenith angle in regions over weak (|B-c|<20nT) and strong (|B-c|>20nT) crustal magnetic fields, and we find clear and consistent evidence for a significant asymmetry between these two regions. We show that within the approximate to 300-1200km altitude range sampled, the median plasma density is substantially higher on the dayside in regions of relatively stronger crustal fields than under equivalent illuminations in regions of relatively weaker crustal fields. Conversely, on the nightside, median plasma densities are found to be higher in regions of relatively weaker crustal fields. We suggest that the observed asymmetry arises as a result of the modulation of the efficiency of plasma transport processes by the irregular crustal fields and the generally horizontal draped interplanetary magnetic field.

  • 5.
    Andrews, David J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Leyser, Thomas B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Buchert, Stephan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morgan, D. D.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA USA.
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA USA.
    Kopf, A. J.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA USA.
    Fallows, K.
    Boston Univ, Ctr Space Phys, Boston, MA USA.
    Withers, P.
    Boston Univ, Ctr Space Phys, Boston, MA USA; Boston Univ, Dept Astron, Commonwealth Ave, Boston, MA USA.
    MARSIS Observations of Field-Aligned Irregularities and Ducted Radio Propagation in the Martian Ionosphere2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 8, p. 6251-6263Article in journal (Refereed)
    Abstract [en]

    Knowledge of Mars's ionosphere has been significantly advanced in recent years by observations from Mars Express and lately Mars Atmosphere and Volatile EvolutioN. A topic of particular interest are the interactions between the planet's ionospheric plasma and its highly structured crustal magnetic fields and how these lead to the redistribution of plasma and affect the propagation of radio waves in the system. In this paper, we elucidate a possible relationship between two anomalous radar signatures previously reported in observations from the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument on Mars Express. Relatively uncommon observations of localized, extreme increases in the ionospheric peak density in regions of radial (cusp-like) magnetic fields and spread echo radar signatures are shown to be coincident with ducting of the same radar pulses at higher altitudes on the same field lines. We suggest that these two observations are both caused by a high electric field (perpendicular to B) having distinctly different effects in two altitude regimes. At lower altitudes, where ions are demagnetized and electrons magnetized, and recombination dominantes, a high electric field causes irregularities, plasma turbulence, electron heating, slower recombination, and ultimately enhanced plasma densities. However, at higher altitudes, where both ions and electrons are magnetized and atomic oxygen ions cannot recombine directly, the high electric field instead causes frictional heating, a faster production of molecular ions by charge exchange, and so a density decrease. The latter enables ducting of radar pulses on closed field lines, in an analogous fashion to interhemispheric ducting in the Earth's ionosphere.

  • 6. Bertucci, C.
    et al.
    Hamilton, D. C.
    Kurth, W. S.
    Hospodarsky, G.
    Mitchell, D.
    Sergis, N.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dougherty, M. K.
    Titan's interaction with the supersonic solar wind2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 2, p. 193-200Article in journal (Refereed)
    Abstract [en]

    After 9years in the Saturn system, the Cassini spacecraft finally observed Titan in the supersonic and super-Alfvenic solar wind. These unique observations reveal that Titan's interaction with the solar wind is in many ways similar to unmagnetized planets Mars and Venus and active comets in spite of the differences in the properties of the solar plasma in the outer solar system. In particular, Cassini detected a collisionless, supercritical bow shock and a well-defined induced magnetosphere filled with mass-loaded interplanetary magnetic field lines, which drape around Titan's ionosphere. Although the flyby altitude may not allow the detection of an ionopause, Cassini reports enhancements of plasma density compatible with plasma clouds or streamers in the flanks of its induced magnetosphere or due to an expansion of the induced magnetosphere. Because of the upstream conditions, these observations may be also relevant to other bodies in the outer solar system such as Pluto, where kinetic processes are expected to dominate.

  • 7. Coates, A. J.
    et al.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cui, J.
    Wellbrock, A.
    Szego, K.
    Recent Results from Titan's Ionosphere2011In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 162, no 1-4, p. 85-111Article, review/survey (Refereed)
    Abstract [en]

    Titan has the most significant atmosphere of any moon in the solar system, with a pressure at the surface larger than the Earth's. It also has a significant ionosphere, which is usually immersed in Saturn's magnetosphere. Occasionally it exits into Saturn's magnetosheath. In this paper we review several recent advances in our understanding of Titan's ionosphere, and present some comparisons with the other unmagnetized objects Mars and Venus. We present aspects of the ionospheric structure, chemistry, electrodynamic coupling and transport processes. We also review observations of ionospheric photoelectrons at Titan, Mars and Venus. Where appropriate, we mention the effects on ionospheric escape.

  • 8.
    Cui, J.
    et al.
    Sun Yat Sen Univ, Sch Atmospher Sci, Zhuhai, Guangdong, Peoples R China;Chinese Acad Sci, Natl Astron Observ, Key Lab Lunar & Deep Space Explorat, Beijing, Peoples R China;Chinese Acad Sci, Ctr Excellence Comparat Planetol, Hefei, Anhui, Peoples R China.
    Cao, Y-T
    Chinese Acad Sci, Natl Astron Observ, Key Lab Lunar & Deep Space Explorat, Beijing, Peoples R China.
    Wu, X-S
    Chinese Acad Sci, Natl Astron Observ, Key Lab Lunar & Deep Space Explorat, Beijing, Peoples R China;Chinese Acad Sci, Ctr Excellence Comparat Planetol, Hefei, Anhui, Peoples R China.
    Xu, S-S
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.
    Yelle, R. , V
    Stone, S.
    Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Shen, C-L
    Chinese Acad Sci, Ctr Excellence Comparat Planetol, Hefei, Anhui, Peoples R China;Univ Sci & Technol China, Sch Earth & Space Sci, Hefei, Anhui, Peoples R China.
    He, F.
    Chinese Acad Sci, Inst Geol & Geophys, Beijing, Peoples R China.
    Wei, Y.
    Chinese Acad Sci, Inst Geol & Geophys, Beijing, Peoples R China.
    Evaluating Local Ionization Balance in the Nightside Martian Upper Atmosphere during MAVEN Deep Dip Campaigns2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 876, no 1, article id L12Article in journal (Refereed)
    Abstract [en]

    Combining the Mars Atmosphere and Volatile Evolution (MAVEN) measurements of atmospheric neutral and ion densities, electron temperature, and energetic electron intensity, we perform the first quantitative evaluation of local ionization balance in the nightside Martian upper atmosphere, a condition with the electron impact ionization (EI) of CO2 exactly balanced by the dissociative recombination (DR) of ambient ions. The data accumulated during two MAVEN Deep Dip (DD) campaigns are included: DD6 on the deep nightside with a periapsis solar zenith angle (SZA) of 165 degrees, and DD3 close to the dawn terminator with a periapsis SZA of 110 degrees. With the electron temperatures at low altitudes corrected for an instrumental effect pertaining to the MAVEN Langmuir Probe and Waves, a statistical agreement between the EI and DR rates is suggested by the data below 140 km during DD6 and below 180 km during DD3, implying that electron precipitation is responsible for the nightside Martian ionosphere under these circumstances and extra sources are not required. In contrast, a substantial enhancement in EI over DR is observed at higher altitudes during both campaigns, which we interpret as a signature of plasma escape down the tail.

  • 9.
    Desai, R. T.
    et al.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Coates, A. J.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Wellbrock, A.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Vuitton, V.
    Univ Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France..
    Crary, F. J.
    Univ Colorado, Lab Atmospher & Space Phys, Innovat Dr, Boulder, CO 80303 USA..
    Gonzalez-Caniulef, D.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England..
    Shebanits, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Jones, G. H.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Lewis, G. R.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England..
    Waite, J. H.
    Southwest Res Inst SWRI, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Cordiner, M.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA..
    Taylor, S. A.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Kataria, D. O.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England..
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sittler, E. C.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA..
    Carbon Chain Anions and the Growth of Complex Organic Molecules in Titan's Ionosphere2017In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 844, no 2, article id L18Article in journal (Refereed)
    Abstract [en]

    Cassini discovered a plethora of neutral and ionized molecules in Titan's ionosphere including, surprisingly, anions and negatively charged molecules extending up to 13,800 u q-1. In this Letter, we forward model the Cassini electron spectrometer response function to this unexpected ionospheric component to achieve an increased mass resolving capability for negatively charged species observed at Titan altitudes of 950-1300 km. We report on detections consistently centered between 25.8 and 26.0 u q-1 and between 49.0-50.1 u q(-1) which are identified as belonging to the carbon chain anions, CN-/C3N- and/or C2H-/C4H-, in agreement with chemical model predictions. At higher ionospheric altitudes, detections at 73-74 u q-1 could be attributed to the further carbon chain anions C5N-/C6H- but at lower altitudes and during further encounters extend over a higher mass/charge range. This, as well as further intermediary anions detected at > 100 u, provide the first evidence for efficient anion chemistry in space involving structures other than linear chains. Furthermore, at altitudes below < 1100 km, the low-mass anions (< 150 u q-1) were found to deplete at a rate proportional to the growth of the larger molecules, a correlation that indicates the anions are tightly coupled to the growth process. This study adds Titan to an increasing list of astrophysical environments where chain anions have been observed and shows that anion chemistry plays a role in the formation of complex organics within a planetary atmosphere as well as in the interstellar medium.

  • 10. Dieval, C.
    et al.
    Stenberg, G.
    Nilsson, H.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Barabash, S.
    Reduced proton and alpha particle precipitations at Mars during solar wind pressure pulses: Mars Express results2013In: Journal of Geophysical Research-Space Physics, ISSN 2169-9380, Vol. 118, no 6, p. 3421-3429Article in journal (Refereed)
    Abstract [en]

    We performed a statistical study of downward moving protons and alpha particles of similar to keV energy (assumed to be of solar wind origin) inside the Martian induced magnetosphere from July 2006 to July 2010. Ion and electron data are from the Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) package on board Mars Express. We investigated the solar wind ion entry into the ionosphere, excluding intervals of low-altitude magnetosheath encounters. The study compares periods of quiet solar wind conditions and periods of solar wind pressure pulses, including interplanetary coronal mass ejections and corotating interaction regions. The solar wind ion precipitation appears localized and/or intermittent, consistent with previous measurements. Precipitation events are less frequent, and the precipitating fluxes do not increase during pressure pulse encounters. During pressure pulses, the occurrence frequency of observed proton precipitation events is reduced by a factor of similar to 3, and for He2+ events the occurrence frequency is reduced by a factor of similar to 2. One explanation is that during pressure pulse periods, the mass loading of the solar wind plasma increases due to a deeper penetration of the interplanetary magnetic flux tubes into the ionosphere. The associated decrease of the solar wind speed thus increases the pileup of the interplanetary magnetic field on the dayside of the planet. The magnetic barrier becomes thicker in terms of solar wind ion gyroradii, causing the observed reduction of H+/He2+ precipitations.

  • 11. Dubinin, E.
    et al.
    Fraenz, M.
    Fedorov, A.
    Lundin, R.
    Edberg, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Duru, F.
    Vaisberg, O.
    Ion Energization and Escape on Mars and Venus2011In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 162, no 1-4, p. 173-211Article, review/survey (Refereed)
    Abstract [en]

    Mars and Venus do not have a global magnetic field and as a result solar wind interacts directly with their ionospheres and upper atmospheres. Neutral atoms ionized by solar UV, charge exchange and electron impact, are extracted and scavenged by solar wind providing a significant loss of planetary volatiles. There are different channels and routes through which the ionized planetary matter escapes from the planets. Processes of ion energization driven by direct solar wind forcing and their escape are intimately related. Forces responsible for ion energization in different channels are different and, correspondingly, the effectiveness of escape is also different. Classification of the energization processes and escape channels on Mars and Venus and also their variability with solar wind parameters is the main topic of our review. We will distinguish between classical pickup and 'mass-loaded' pickup processes, energization in boundary layer and plasma sheet, polar winds on unmagnetized planets with magnetized ionospheres and enhanced escape flows from localized auroral regions in the regions filled by strong crustal magnetic fields.

  • 12.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Alho, M.
    Aalto Univ, Sch Elect Engn, Dept Radio Sci & Engn, POB 13000, FI-00076 Aalto, Finland..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Behar, E.
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden..
    Burch, J. L.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Carr, C. M.
    Imperial Coll London, Exhibit Rd, London SW7 2AZ, England..
    Cupido, E.
    Imperial Coll London, Exhibit Rd, London SW7 2AZ, England..
    Engelhardt, Ilka. A. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Glassmeier, K. -H
    Goetz, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Goldstein, R.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Henri, P.
    Lab Phys & Chim Environm & Espace, F-45071 Orleans 2, France..
    Johansson, Fredrik L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Koenders, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Mandt, K.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Moestl, C.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    Nilsson, H.
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden..
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Wedlund, C. Simon
    Univ Oslo, Dept Phys, Box 1048 Blindern, N-0316 Oslo, Norway..
    Wieser, G. Stenberg
    Swedish Inst Space Phys, Box 812, SE-98128 Kiruna, Sweden..
    Szego, K.
    Wigner Res Ctr Phys, Konkoly Thege Miklos Ut 29-33, H-1121 Budapest, Hungary..
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Volwerk, M.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    CME impact on comet 67P/Churyumov-Gerasimenko2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S45-S56Article in journal (Refereed)
    Abstract [en]

    We present Rosetta observations from comet 67P/Churyumov-Gerasimenko during the impact of a coronal mass ejection (CME). The CME impacted on 2015 Oct 5-6, when Rosetta was about 800 km from the comet nucleus, and 1.4 au from the Sun. Upon impact, the plasma environment is compressed to the level that solar wind ions, not seen a few days earlier when at 1500 km, now reach Rosetta. In response to the compression, the flux of suprathermal electrons increases by a factor of 5-10 and the background magnetic field strength increases by a factor of similar to 2.5. The plasma density increases by a factor of 10 and reaches 600 cm(-3), due to increased particle impact ionization, charge exchange and the adiabatic compression of the plasma environment. We also observe unprecedentedly large magnetic field spikes at 800 km, reaching above 200 nT, which are interpreted as magnetic flux ropes. We suggest that these could possibly be formed by magnetic reconnection processes in the coma as the magnetic field across the CME changes polarity, or as a consequence of strong shears causing Kelvin-Helmholtz instabilities in the plasma flow. Due to the limited orbit of Rosetta, we are not able to observe if a tail disconnection occurs during the CME impact, which could be expected based on previous remote observations of other CME-comet interactions.

  • 13.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Bertucci, C.
    IAFE, Buenos Aires, DF, Argentina..
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Holmberg, Mika K. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Jackman, C. M.
    Univ Southampton, Southampton, Hants, England..
    Kurth, W. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Menietti, J. D.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Shebanits, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Effects of Saturn's magnetospheric dynamics on Titan's ionosphere2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 10, p. 8884-8898Article in journal (Refereed)
    Abstract [en]

    We use the Cassini Radio and Plasma Wave Science/Langmuir probe measurements of the electron density from the first 110 flybys of Titan to study how Saturn's magnetosphere influences Titan's ionosphere. The data is first corrected for biased sampling due to varying solar zenith angle and solar energy flux (solar cycle effects). We then present results showing that the electron density in Titan's ionosphere, in the altitude range 1600-2400km, is increased by about a factor of 2.5 when Titan is located on the nightside of Saturn (Saturn local time (SLT) 21-03h) compared to when on the dayside (SLT 09-15 h). For lower altitudes (1100-1600km) the main dividing factor for the ionospheric density is the ambient magnetospheric conditions. When Titan is located in the magnetospheric current sheet, the electron density in Titan's ionosphere is about a factor of 1.4 higher compared to when Titan is located in the magnetospheric lobes. The factor of 1.4 increase in between sheet and lobe flybys is interpreted as an effect of increased particle impact ionization from approximate to 200eV sheet electrons. The factor of 2.5 increase in electron density between flybys on Saturn's nightside and dayside is suggested to be an effect of the pressure balance between thermal plus magnetic pressure in Titan's ionosphere against the dynamic pressure and energetic particle pressure in Saturn's magnetosphere.

  • 14.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Shebanits, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Ågren, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cravens, T. E.
    Girazian, Z.
    Solar cycle modulation of Titan's ionosphere2013In: Journal of Geophysical Research-Space Physics, ISSN 2169-9380, Vol. 118, no 8, p. 5255-5264Article in journal (Refereed)
    Abstract [en]

    During the six Cassini Titan flybys T83-T88 (May 2012 to November 2012) the electron density in the ionospheric peak region, as measured by the radio and plasma wave science instrument/Langmuir probe, has increased significantly, by 15-30%, compared to previous average. These measurements suggest that a longterm change has occurred in the ionosphere of Titan, likely caused by the rise to the new solar maximum with increased EUV fluxes. We compare measurements from TA, TB, and T5, from the declining phase of solar cycle 23 to the recent T83-T88 measurements during cycle 24, since the solar irradiances from those two intervals are comparable. The peak electron densities normalized to a common solar zenith angle N-norm from those two groups of flybys are comparable but increased compared to the solar minimum flybys (T16-T71). The integrated solar irradiance over the wavelengths 1-80nm, i.e., the solar energy flux, F-e, correlates well with the observed ionospheric peak density values. Chapman layer theory predicts that Nnorm<mml:msubsup>Fek</mml:msubsup>, with k=0.5. We find observationally that the exponent k=0.540.18. Hence, the observations are in good agreement with theory despite the fact that many assumptions in Chapman theory are violated. This is also in good agreement with a similar study by Girazian and Withers (2013) on the ionosphere of Mars. We use this power law to estimate the peak electron density at the subsolar point of Titan during solar maximum conditions and find it to be about 6500cm(-3), i.e., 85-160% more than has been measured during the entire Cassini mission.

  • 15.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Shebanits, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Roussos, E.
    Garnier, P.
    Cravens, T. E.
    Badman, S. V.
    Modolo, R.
    Bertucci, C.
    Dougherty, M. K.
    Extreme densities in Titan's ionosphere during the T85 magnetosheath encounter2013In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, no 12, p. 2879-2883Article in journal (Refereed)
    Abstract [en]

    We present Cassini Langmuir probe measurements of the highest electron number densities ever reported from the ionosphere of Titan. The measured density reached 4310cm(-3) during the T85 Titan flyby. This is at least 500cm(-3) higher than ever observed before and at least 50% above the average density for similar solar zenith angles. The peak of the ionospheric density is not reached on this flyby, making the maximum measured density a lower limit. During this flyby, we also report that an impacting coronal mass ejection (CME) leaves Titan in the magnetosheath of Saturn, where it is exposed to shocked solar wind plasma for at least 2 h 45 min. We suggest that the solar wind plasma in the magnetosheath during the CME conditions significantly modifies Titan's ionosphere by an addition of particle impact ionization by precipitating protons.

  • 16.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Henri, P.
    Lebreton, J. -P
    Gasc, S.
    Rubin, M.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gill, Reine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Erik P. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Carr, C. M.
    Cupido, E.
    Glassmeier, K. -H
    Goldstein, R.
    Koenders, C.
    Mandt, K.
    Nemeth, Z.
    Nilsson, H.
    Richter, I.
    Wieser, G. Stenberg
    Szego, K.
    Volwerk, M.
    Spatial distribution of low-energy plasma around comet 67P/CG from Rosetta measurements2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 11, p. 4263-4269Article in journal (Refereed)
    Abstract [en]

    We use measurements from the Rosetta plasma consortium Langmuir probe and mutual impedance probe to study the spatial distribution of low-energy plasma in the near-nucleus coma of comet 67P/Churyumov-Gerasimenko. The spatial distribution is highly structured with the highest density in the summer hemisphere and above the region connecting the two main lobes of the comet, i.e., the neck region. There is a clear correlation with the neutral density and the plasma to neutral density ratio is found to be approximate to 1-210(-6), at a cometocentric distance of 10km and at 3.1AU from the Sun. A clear 6.2h modulation of the plasma is seen as the neck is exposed twice per rotation. The electron density of the collisionless plasma within 260km from the nucleus falls off with radial distance as approximate to 1/r. The spatial structure indicates that local ionization of neutral gas is the dominant source of low-energy plasma around the comet.

  • 17.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, D. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Burch, J. L.
    SW Res Inst, San Antonio, TX USA..
    Carr, C. M.
    Univ London Imperial Coll Sci Technol & Med, Space & Atmospher Phys Grp, London, England..
    Cupido, E.
    Univ London Imperial Coll Sci Technol & Med, Space & Atmospher Phys Grp, London, England..
    Glassmeier, K. -H
    Goldstein, R.
    SW Res Inst, San Antonio, TX USA..
    Halekas, J. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Henri, P.
    Lab Phys & Chim Environm & Espace, Orleans, France..
    Koenders, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany..
    Mandt, K.
    SW Res Inst, San Antonio, TX USA..
    Mokashi, P.
    SW Res Inst, San Antonio, TX USA..
    Nemeth, Z.
    Wigner Res Ctr Phys, Budapest, Hungary..
    Nilsson, H.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Ramstad, R.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany..
    Wieser, G. Stenberg
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Solar wind interaction with comet 67P: Impacts of corotating interaction regions2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 2, p. 949-965Article in journal (Refereed)
    Abstract [en]

    We present observations from the Rosetta Plasma Consortium of the effects of stormy solar wind on comet 67P/Churyumov-Gerasimenko. Four corotating interaction regions (CIRs), where the first event has possibly merged with a coronal mass ejection, are traced from Earth via Mars (using Mars Express and Mars Atmosphere and Volatile EvolutioN mission) to comet 67P from October to December 2014. When the comet is 3.1-2.7AU from the Sun and the neutral outgassing rate approximate to 10(25)-10(26)s(-1), the CIRs significantly influence the cometary plasma environment at altitudes down to 10-30km. The ionospheric low-energy (approximate to 5eV) plasma density increases significantly in all events, by a factor of >2 in events 1 and 2 but less in events 3 and 4. The spacecraft potential drops below -20V upon impact when the flux of electrons increases. The increased density is likely caused by compression of the plasma environment, increased particle impact ionization, and possibly charge exchange processes and acceleration of mass-loaded plasma back to the comet ionosphere. During all events, the fluxes of suprathermal (approximate to 10-100eV) electrons increase significantly, suggesting that the heating mechanism of these electrons is coupled to the solar wind energy input. At impact the magnetic field strength in the coma increases by a factor of 2-5 as more interplanetary magnetic field piles up around the comet. During two CIR impact events, we observe possible plasma boundaries forming, or moving past Rosetta, as the strong solar wind compresses the cometary plasma environment. We also discuss the possibility of seeing some signatures of the ionospheric response to tail disconnection events.

  • 18.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Goetz, Charlotte
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany.
    Nilsson, Hans
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden;Lulea Univ Technol, Dept Comp Sci Elect & Space Engn, Rymdcampus 1, SE-98128 Kiruna, Sweden.
    Gilet, Nicolas
    CNRS, LPC2E, Orleans, France.
    Henri, Pierre
    CNRS, LPC2E, Orleans, France.
    The Convective Electric Field Influence on the Cold Plasma and Diamagnetic Cavity of Comet 67P2019In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 158, no 2, article id 71Article in journal (Refereed)
    Abstract [en]

    We studied the distribution of cold electrons (<1 eV) around comet 67P/Churyumov-Gerasimenko with respect to the solar wind convective electric field direction. The cold plasma was measured by the Langmuir Probe instrument and the direction of the convective electric field E-conv = -nu x B was determined from magnetic field (B) measurements inside the coma combined with an assumption of a purely radial solar wind velocity nu. We found that the cold plasma is twice as likely to be observed when the convective electric field at Rosetta's position is directed toward the nucleus (in the -E(conv )hemisphere) compared to when it is away from the nucleus (in the +E-conv hemisphere). Similarly, the diamagnetic cavity, in which previous studies have shown that cold plasma is always present, was also found to be observed twice as often when in the -E-conv hemisphere, linking its existence circumstantially to the presence of cold electrons. The results are consistent with hybrid and Hall magnetohydrodynamic simulations as well as measurements of the ion distribution around the diamagnetic cavity.

  • 19.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Snowden, D.
    Cent Washington Univ, Dept Phys, Ellensburg, WA USA.
    Regoli, L. H.
    Univ Michigan, Climate & Space Sci & Engn, Ann Arbor, MI 48109 USA.
    Shebanits, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Imperial Coll London, Dept Phys, London, England.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Bertucci, C.
    IAFE, Ciudad Univ, Buenos Aires, DF, Argentina.
    Cui, J.
    Sun Yat Sen Univ, Sch Atmospher Sci, Zhuhai, Peoples R China;Chinese Acad Sci, Key Lab Lunar & Deep Space Explorat, Beijing, Peoples R China.
    Titan's Variable Ionosphere During the T118 and T119 Cassini Flybys2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 17, p. 8721-8728Article in journal (Refereed)
    Abstract [en]

    We report on unusual dynamics in Titan's ionosphere as a significant difference in ionospheric electron density is observed between the T118 and T119 Cassini nightside flybys. Two distinct nightside electron density peaks were present during T118, at 1,150 and 1,200km, and the lowest density ever observed in Titan's ionosphere at altitudes 1,000-1,350km was during T118. These flybys were quite similar in geometry, Saturn local time, neutral density, extreme ultraviolet flux, and ambient magnetic field conditions. Despite this, the Radio and Plasma Waves/Langmuir Probe measured a density difference up to a factor of 6 between the passes. The overall difference was present and similar during both inbound and outbound legs. By ruling out other factors, we suggest that an exceptionally low rate of particle impact ionization in combination with dynamics in the ionosphere is the explanation for the observations. Plain Language Summary Using the Cassini satellite in orbit around Saturn, we make measurements during two close passes of the moon Titan. We observe how the electron density in the uppermost part of the moon's atmosphere-the ionosphere-changes drastically from one pass to the next. We also observe unexpectedly high peaks of electron density in a specific altitude range during the first pass. The findings are attributed to low influx of charged particles from Saturn's magnetosphere as well as to increased dynamics of the plasma in the ionosphere. The study emphasizes the complexity of the physical process at play at the moon and aims at gaining further understanding of this environment.

  • 20.
    Edberg, Niklas J. T.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morooka, Michiko W.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, D. J.
    Cowley, S. W. H.
    Wellbrock, A.
    Coates, A. J.
    Bertucci, C.
    Dougherty, M. K.
    Structured ionospheric outflow during the Cassini T55-T59 Titan flybys2011In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 59, no 8, p. 788-797Article in journal (Refereed)
    Abstract [en]

    During the final three of the five consecutive and similar Cassini Titan flybys T55-T59 we observe a region characterized by high plasma densities (electron densities of 1-8 cm(-3)) in the tail/nightside of Titan. This region is observed progressively farther downtail from pass to pass and is interpreted as a plume of ionospheric plasma escaping Titan, which appears steady in both location and time. The ions in this plasma plume are moving in the direction away from Titan and are a mixture of both light and heavy ions with composition revealing that their origin are in Titan's ionosphere, while the electrons are more isotropically distributed. Magnetic field measurements indicate the presence of a current sheet at the inner edge of this region. We discuss the mechanisms behind this outflow, and suggest that it could be caused by ambipolar diffusion, magnetic moment pumping or dispersive Alfven waves.

  • 21.
    Eriksson, Anders I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Engelhardt, Ilka. A. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Boström, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Henri, P.
    LPC2E, Lab Phys & Chim Environm & Espace.
    Lebreton, J. -P
    LPC2E, Lab Phys & Chim Environm & Espace.
    Miloch, W. J.
    Univ Oslo, Dept Phys.
    Paulsson, J. J. P.
    Univ Oslo, Dept Phys.
    Wedlund, Cyril Simon
    Univ Oslo, Dept Phys.
    Yang, L.
    Univ Oslo, Dept Phys.
    Karlsson, T.
    Royal Inst Technol, Alfvén Lab.
    Jarvinen, R.
    Finnish Meteorol Inst, Helsinki 00560.
    Broiles, Thomas
    Southwest Res Inst, San Antonio.
    Mandt, K.
    Southwest Res Inst, San Antonio; Univ Texas San Antonio, Dept Phys & Astron.
    Carr, C. M.
    Imperial Coll London, Dept Phys.
    Galand, M.
    Imperial Coll London, Dept Phys.
    Nilsson, H.
    Swedish Inst Space Phys, S-98128 Kiruna.
    Norberg, C.
    Swedish Inst Space Phys, S-98128 Kiruna.
    Cold and warm electrons at comet 67P/Churyumov-Gerasimenko2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 605, article id A15Article in journal (Refereed)
    Abstract [en]

    Context. Strong electron cooling on the neutral gas in cometary comae has been predicted for a long time, but actual measurements of low electron temperature are scarce. Aims. Our aim is to demonstrate the existence of cold electrons in the inner coma of comet 67P/Churyumov-Gerasimenko and show filamentation of this plasma.

    Methods. In situ measurements of plasma density, electron temperature and spacecraft potential were carried out by the Rosetta Langmuir probe instrument, LAP. We also performed analytical modelling of the expanding two-temperature electron gas.

    Results. LAP data acquired within a few hundred km from the nucleus are dominated by a warm component with electron temperature typically 5-10 eV at all heliocentric distances covered (1.25 to 3.83 AU). A cold component, with temperature no higher than about 0.1 eV, appears in the data as short (few to few tens of seconds) pulses of high probe current, indicating local enhancement of plasma density as well as a decrease in electron temperature. These pulses first appeared around 3 AU and were seen for longer periods close to perihelion. The general pattern of pulse appearance follows that of neutral gas and plasma density. We have not identified any periods with only cold electrons present. The electron flux to Rosetta was always dominated by higher energies, driving the spacecraft potential to order -10 V.

    Conclusions. The warm (5-10 eV) electron population observed throughout the mission is interpreted as electrons retaining the energy they obtained when released in the ionisation process. The sometimes observed cold populations with electron temperatures below 0.1 eV verify collisional cooling in the coma. The cold electrons were only observed together with the warm population. The general appearance of the cold population appears to be consistent with a Haser-like model, implicitly supporting also the coupling of ions to the neutral gas. The expanding cold plasma is unstable, forming filaments that we observe as pulses.

  • 22.
    Feyerabend, Moritz
    et al.
    Univ Cologne, Inst Geophys & Meteorol, Cologne, Germany.;Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA..
    Simon, Sven
    Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA..
    Neubauer, Fritz M.
    Univ Cologne, Inst Geophys & Meteorol, Cologne, Germany..
    Motschmann, Uwe
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Theoret Phys, Braunschweig, Germany.;German Aerosp Ctr, Inst Planetary Res, Berlin, Germany..
    Bertucci, Cesar
    Univ Buenos Aires, CONICET, Inst Astron & Space Phys, Ciudad Univ, Buenos Aires, DF, Argentina..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Hospodarsky, George B.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Kurth, William S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Hybrid simulation of Titan's interaction with the supersonic solar wind during Cassini's T96 flyby2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 1, p. 35-42Article in journal (Refereed)
    Abstract [en]

    By applying a hybrid (kinetic ions and fluid electrons) simulation code, we study the plasma environment of Saturn's largest moon Titan during Cassini's T96 flyby on 1 December 2013. The T96 encounter marks the only observed event of the entire Cassini mission where Titan was located in the supersonic solar wind in front of Saturn's bow shock. Our simulations can quantitatively reproduce the key features of Cassini magnetic field and electron density observations during this encounter. We demonstrate that the large-scale features of Titan's induced magnetosphere during T96 can be described in terms of a steady state interaction with a high-pressure solar wind flow. About 40min before the encounter, Cassini observed a rotation of the incident solar wind magnetic field by almost 90 degrees. We provide strong evidence that this rotation left a bundle of fossilized magnetic field lines in Titan's ionosphere that was subsequently detected by the spacecraft.

  • 23.
    Grun, E.
    et al.
    Max Planck Inst Kernphys, Saupfercheckweg 1, D-69127 Heidelberg, Germany.;Univ Colorado, Lab Atmospher & Space Phys, 1234 Innovat Dr, Boulder, CO 80303 USA..
    Agarwal, J.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Altobelli, N.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain..
    Altwegg, K.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Bentley, M. S.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    Biver, N.
    Univ Paris Diderot, UPMC, CNRS, LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Della Corte, V.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Feldman, P. D.
    Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA..
    Galand, M.
    Imperial Coll, South Kensington Campus, London SW7 2AZ, England..
    Geiger, B.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain..
    Goetz, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany..
    Grieger, B.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain..
    Guettler, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Henri, P.
    CNRS, LPC2E, Orleans, France..
    Hofstadter, M.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Horanyi, M.
    Univ Colorado, Lab Atmospher & Space Phys, 1234 Innovat Dr, Boulder, CO 80303 USA..
    Jehin, E.
    Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium..
    Krueger, H.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Lee, S.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Mannel, T.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria..
    Morales, E.
    Jaicoa Observ, Aguadilla, PR USA..
    Mousis, O.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France..
    Mueller, M.
    ESOC, ESA, Robert Bosch Str 5, Darmstadt, Germany..
    Opitom, C.
    Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium..
    Rotundi, A.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy.;Univ Napoli Parthenope, Dip Sci & Tecnol, CDN IC4, I-80143 Naples, Italy..
    Schmied, R.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria.;Graz Univ, Inst Phys, Univ Pl 3, A-8010 Graz, Austria..
    Schmidt, F.
    Univ Stuttgart, Inst Raumfahrtsyst IRS, Pfaffenwaldring 29, D-70569 Stuttgart, Germany..
    Sierks, H.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Snodgrass, C.
    Open Univ, Dept Phys Sci, Planetary & Space Sci, Milton Keynes MK7 6AA, Bucks, England..
    Soja, R. H.
    Univ Stuttgart, Inst Raumfahrtsyst IRS, Pfaffenwaldring 29, D-70569 Stuttgart, Germany..
    Sommer, M.
    Univ Stuttgart, Inst Raumfahrtsyst IRS, Pfaffenwaldring 29, D-70569 Stuttgart, Germany..
    Srama, R.
    Univ Stuttgart, Inst Raumfahrtsyst IRS, Pfaffenwaldring 29, D-70569 Stuttgart, Germany..
    Tzou, C. -Y
    Vincent, J. -B
    Yanamandra-Fisher, P.
    Space Sci Inst, 13456 Cajon Creek Court, Rancho Cucamonga, CA 91739 USA..
    A'Hearn, M. F.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Barbieri, C.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Barucci, M. A.
    Univ Paris Diderot, UPMC, CNRS, LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Bertaux, J. -L
    Bertini, I.
    Univ Padua, Ctr Ateneo Studi Attivita Spaziali Giusepp Colomb, Via Venezia 15, I-35131 Padua, Italy..
    Burch, J.
    Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Colangeli, L.
    European Space Agcy, European Space Res & Technol Ctr, Keplerlaan 1, NL-2201 AZ Noordwijk, Netherlands..
    Cremonese, G.
    Osserv Astron Padova, INAF, Vicolo Osservatorio 5, I-35122 Padua, Italy..
    Da Deppo, V.
    CNR, IFN UOS Padova LUXOR, Via Trasea 7, I-35131 Padua, Italy..
    Davidsson, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
    Debei, S.
    Univ Padua, Dept Ind Engn, Via Venezia 1, I-35131 Padua, Italy..
    De Cecco, M.
    Osserv Astron Trieste, INAF, Via Tiepolo 11, I-34143 Trieste, Italy..
    Deller, J.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Feaga, L. M.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Ferrari, M.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy..
    Fornasier, S.
    Univ Paris Diderot, UPMC, CNRS, LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Fulle, M.
    Osserv Astron Trieste, INAF, Via Tiepolo 11, I-34143 Trieste, Italy..
    Gicquel, A.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Gillon, M.
    Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium..
    Green, S. F.
    Open Univ, Dept Phys Sci, Planetary & Space Sci, Milton Keynes MK7 6AA, Bucks, England..
    Groussin, O.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France..
    Gutierrez, P. J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron, E-18008 Granada, Spain..
    Hofmann, M.
    Hviid, S. F.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Ip, W. -H
    Ivanovski, S.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy..
    Jorda, L.
    Aix Marseille Univ, CNRS, LAM, UMR 7326, F-13388 Marseille, France..
    Keller, H. U.
    TU Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany..
    Knight, M. M.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Knollenberg, J.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Koschny, D.
    European Space Agcy, European Space Res & Technol Ctr, Keplerlaan 1, NL-2201 AZ Noordwijk, Netherlands..
    Kramm, J. -R
    Kuehrt, E.
    DLR, Inst Planetary Res, Rutherfordstr 2, D-12489 Berlin, Germany..
    Kuppers, M.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain..
    Lamy, P. L.
    CNRS, UMR 7326, Lab Astrophys Marseille, 38 Rue Federic Joliot Curie, F-13388 Marseille 13, France.;Aix Marseille Univ, 38 Rue Federic Joliot Curie, F-13388 Marseille 13, France..
    Lara, L. M.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron, E-18008 Granada, Spain..
    Lazzarin, M.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Lopez-Moreno, J. J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, E-18008 Granada, Spain..
    Manfroid, J.
    Univ Liege, Inst Astrophys & Geophys, B-4000 Liege, Belgium..
    Epifani, E. Mazzotta
    OAR, INAF, Via Frascati 33, I-00078 Rome, Italy..
    Marzari, F.
    Univ Padua, Dept Phys & Astron G Galilei, Vic Osservatorio 3, I-35122 Padua, Italy..
    Naletto, G.
    Univ Padua, Ctr Ateneo Studi Attivita Spaziali Giusepp Colomb, Via Venezia 15, I-35131 Padua, Italy.;Univ Padua, Dept Informat Engn, Via Gradenigo 6-B, I-35131 Padua, Italy..
    Oklay, N.
    Palumbo, P.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy.;Univ Napoli Parthenope, Dip Sci & Tecnol, CDN IC4, I-80143 Naples, Italy..
    Parker, J. Wm.
    Southwest Res Inst, 1050 Walnut St,Suite 300, Boulder, CO 80302 USA..
    Rickman, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics. PAS Space Res Ctr, Poland.
    Rodrigo, R.
    ESA, Camino Bajo Castillo S-N, E-28692 Madrid, Spain.;Int Space Sci Inst, Hallerstr 6, CH-3012 Bern, Switzerland..
    Rodriguez, J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, E-18008 Granada, Spain..
    Schindhelm, E.
    Southwest Res Inst, 1050 Walnut St,Suite 300, Boulder, CO 80302 USA..
    Shi, X.
    Sordini, R.
    INAF, IAPS, Via Fosso Cavaliere, I-00133 Rome, Italy..
    Steffl, A. J.
    Southwest Res Inst, 1050 Walnut St,Suite 300, Boulder, CO 80302 USA..
    Stern, S. A.
    Southwest Res Inst, 1050 Walnut St,Suite 300, Boulder, CO 80302 USA..
    Thomas, N.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Tubiana, C.
    Max Planck Inst Sonnensyst Forsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Weaver, H. A.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Weissman, P.
    Planetary Sci Inst, 1700 East Ft Lowell,Suite 106, Tucson, AZ 85719 USA..
    Zakharov, V. V.
    Univ Paris Diderot, UPMC, CNRS, LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France.;UPMC Univ Paris 06, CNRS, Sorbonne Univ, Lab Meteorol Dynam, 4 Pl Jussieu, F-75252 Paris, France..
    The 2016 Feb 19 outburst of comet 67P/CG: an ESA Rosetta multi-instrument study2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S220-S234Article in journal (Refereed)
    Abstract [en]

    On 2016 Feb 19, nine Rosetta instruments serendipitously observed an outburst of gas and dust from the nucleus of comet 67P/Churyumov-Gerasimenko. Among these instruments were cameras and spectrometers ranging from UV over visible to microwave wavelengths, in situ gas, dust and plasma instruments, and one dust collector. At 09: 40 a dust cloud developed at the edge of an image in the shadowed region of the nucleus. Over the next two hours the instruments recorded a signature of the outburst that significantly exceeded the background. The enhancement ranged from 50 per cent of the neutral gas density at Rosetta to factors > 100 of the brightness of the coma near the nucleus. Dust related phenomena (dust counts or brightness due to illuminated dust) showed the strongest enhancements (factors > 10). However, even the electron density at Rosetta increased by a factor 3 and consequently the spacecraft potential changed from similar to-16 V to -20 V during the outburst. A clear sequence of events was observed at the distance of Rosetta ( 34 km from the nucleus): within 15 min the Star Tracker camera detected fast particles (similar to 25 m s(-1)) while 100 mu m radius particles were detected by the GIADA dust instrument similar to 1 h later at a speed of 6 m s(-1). The slowest were individual mm to cm sized grains observed by the OSIRIS cameras. Although the outburst originated just outside the FOV of the instruments, the source region and the magnitude of the outburst could be determined.

  • 24.
    Hadid, Lina Z
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morooka, Michiko W.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Moore, L.
    Boston Univ, Ctr Space Phys, Boston, MA 02215 USA.
    Cravens, T. E.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA.
    Hedman, M. M.
    Univ Idaho, Dept Phys, Moscow, ID USA.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Waite, J. H., Jr.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA.
    Perryman, R.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA.
    Kurth, W. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Farrell, W. M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ring Shadowing Effects on Saturn's Ionosphere: Implications for Ring Opacity and Plasma Transport2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 19, p. 10084-10092Article in journal (Refereed)
    Abstract [en]

    We present new results obtained by the Radio and Plasma Wave Science Langmuir probe on board Cassini during the Grand Finale. The total direct current sampled by the Langmuir probe at negative bias voltage is used to study the effect of the ring shadows on the structure of the Kronian topside ionosphere. The D and C rings and the Cassini Division are confirmed to be optically thin to extreme ultraviolet solar radiation. However, different responses from the opaque A and B rings are observed. The edges of the A ring shadow are shown to match the A ring boundaries, unlike the B ring, which indicates variable responses to the B ring shadow. We show that the variable responses are due to the ionospheric plasma, more precisely to the longer chemical lifetime of H+ compared to H-2(+) and H-3(+), suggesting that the plasma is transported from the sunlit region to the shadowed one in the ionosphere. Plain Language Summary As Saturn's northern hemisphere experienced summer during the Grand Finale, the planet's northern dayside hemisphere and its rings were fully illuminated by the Sun. However, the southern hemisphere was partly obscured because of the shadows cast by the A and B rings. Using the in situ measurements of the Langmuir probe part of the Radio and Plasma Wave Science investigation on board the Cassini spacecraft, we study for the first time the effect of the ring shadows on Saturn's ionosphere. From the ring shadows signatures on the total ion current collected by the Langmuir probe, we show that the A and B rings are optically thicker (to the solar extreme ultraviolet radiation) than the inner C and D rings and the Cassini Division to the solar extreme ultraviolet radiation. Moreover, we reproduce the boundaries of the A ring and the outer edge of the B ring. Furthermore, observed variations with respect to the inner edge of the B ring imply a delayed response of the ionospheric H+ because of its long lifetime and suggest that the ionospheric plasma is transported from an unshadowed region to a shadowed one in the ionosphere.

  • 25.
    Hajra, R.
    et al.
    CNRS, LPC2E, Orleans, France..
    Henri, P.
    CNRS, LPC2E, Orleans, France..
    Vallieres, X.
    CNRS, LPC2E, Orleans, France..
    Galand, M.
    Imperial Coll, South Kensington Campus, London SW7 2AZ, England..
    Heritier, K.
    Imperial Coll, South Kensington Campus, London SW7 2AZ, England..
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Burch, J. L.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Broiles, T.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Goldstein, R.
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA..
    Glassmeier, K. H.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Richter, I.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Goetz, C.
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany..
    Tsurutani, B. T.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Nilsson, H.
    Swedish Inst Space Phys, POB 812, S-98128 Kiruna, Sweden..
    Altwegg, K.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Rubin, M.
    Univ Bern, Phys Inst, Sidlerstr 5, CH-3012 Bern, Switzerland..
    Impact of a cometary outburst on its ionosphere Rosetta Plasma Consortium observations of the outburst exhibited by comet 67P/Churyumov-Gerasimenko on 19 February 20162017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 607, article id A34Article in journal (Refereed)
    Abstract [en]

    We present a detailed study of the cometary ionospheric response to a cometary brightness outburst using in situ measurements for the first time. The comet 67P/Churyumov-Gerasimenko (67P) at a heliocentric distance of 2.4 AU from the Sun, exhibited an outburst at similar to 1000 UT on 19 February 2016, characterized by an increase in the coma surface brightness of two orders of magnitude. The Rosetta spacecraft monitored the plasma environment of 67P from a distance of 30 km, orbiting with a relative speed of similar to 0.2 m s(-1). The onset of the outburst was preceded by pre-outburst decreases in neutral gas density at Rosetta, in local plasma density, and in negative spacecraft potential at similar to 0950 UT. In response to the outburst, the neutral density increased by a factor of similar to 1.8 and the local plasma density increased by a factor of similar to 3, driving the spacecraft potential more negative. The energetic electrons (tens of eV) exhibited decreases in the flux of factors of similar to 2 to 9, depending on the energy of the electrons. The local magnetic field exhibited a slight increase in amplitude (similar to 5 nT) and an abrupt rotation (similar to 36.4 degrees) in response to the outburst. A weakening of 10-100 mHz magnetic field fluctuations was also noted during the outburst, suggesting alteration of the origin of the wave activity by the outburst. The plasma and magnetic field effects lasted for about 4 h, from similar to 1000 UT to 1400 UT. The plasma densities are compared with an ionospheric model. This shows that while photoionization is the main source of electrons, electron-impact ionization and a reduction in the ion outflow velocity need to be accounted for in order to explain the plasma density enhancement near the outburst peak.

  • 26.
    Hajra, Rajkumar
    et al.
    CNRS, LPC2E, F-45071 Orleans, France.
    Henri, Pierre
    CNRS, LPC2E, F-45071 Orleans, France.
    Myllys, Minna
    CNRS, LPC2E, F-45071 Orleans, France.
    Heritier, Kevin L.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Galand, Marina
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England.
    Wedlund, Cyril Simon
    Univ Oslo, Dept Phys, Box 1048 Blindern, N-0316 Oslo, Norway.
    Breuillard, Hugo
    CNRS, LPC2E, F-45071 Orleans, France;Sorbonne Univ, CNRS, Ecole Polytech, Lab Phys Plasmas, 4 Pl Jussieu, F-75252 Paris, France.
    Behar, Etienne
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Goetz, Charlotte
    TU Braunschweig, Inst Geophys & Extraterr Phys, Mendelssohnstr 3, D-38106 Braunschweig, Germany.
    Nilsson, Hans
    Swedish Inst Space Phys, POB 812, SE-98128 Kiruna, Sweden.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Goldstein, Raymond
    Southwest Res Inst, PO Drawer 28510, San Antonio, TX 78228 USA.
    Tsurutani, Bruce T.
    CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA.
    More, Jerome
    CNRS, LPC2E, F-45071 Orleans, France.
    Vallieres, Xavier
    CNRS, LPC2E, F-45071 Orleans, France.
    Wattieauxu, Gaetan
    Univ Toulouse, CNRS, LAPLACE, F-31062 Toulouse, France.
    Cometary plasma response to interplanetary corotating interaction regions during 2016 June-September: a quantitative study by the Rosetta Plasma Consortium2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 480, no 4, p. 4544-4556Article in journal (Refereed)
    Abstract [en]

    Four interplanetary corotating interaction regions (CIRs) were identified during 2016 June-September by the Rosetta Plasma Consortium (RPC) monitoring in situ the plasma environment of the comet 67P/Churyumov-Gerasimenko (67P) at heliocentric distances of similar to 3-3.8 au. The CIRs, formed in the interface region between low- and high-speed solar wind streams with speeds of similar to 320-400 km s(-1) and similar to 580-640 km s(-1), respectively, are characterized by relative increases in solar wind proton density by factors of similar to 13-29, in proton temperature by similar to 7-29, and in magnetic field by similar to 1-4 with respect to the pre-CIR values. The CIR boundaries are well defined with interplanetary discontinuities. Out of 10 discontinuities, four are determined to be forward waves and five are reverse waves, propagating at similar to 5-92 per cent of the magnetosonic speed at angles of similar to 20 degrees-87 degrees relative to ambient magnetic field. Only one is identified to be a quasi-parallel forward shock with magnetosonic Mach number of similar to 1.48 and shock normal angle of similar to 41 degrees. The cometary ionosphere response was monitored by Rosetta from cometocentric distances of similar to 4-30 km. A quiet time plasma density map was developed by considering dependences on cometary latitude, longitude, and cometocentric distance of Rosetta observations before and after each of the CIR intervals. The CIRs lead to plasma density enhancements of similar to 500-1000 per cent with respect to the quiet time reference level. Ionospheric modelling shows that increased ionization rate due to enhanced ionizing (>12-200 eV) electron impact is the prime cause of the large cometary plasma density enhancements during the CIRs. Plausible origin mechanisms of the cometary ionizing electron enhancements are discussed.

  • 27.
    Hall, B. E. S.
    et al.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Lester, M.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Sanchez-Cano, B.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Nichols, J. D.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fränz, M.
    Max Planck Inst Solar Syst Res, Gottingen, Germany..
    Holmström, M.
    Swedish Inst Space Phys, Kiruna Div, Kiruna, Sweden..
    Ramstad, R.
    Swedish Inst Space Phys, Kiruna Div, Kiruna, Sweden..
    Witasse, O.
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Cartacci, M.
    European Space Agcy, Estec, Sci Support Off, Noordwijk, Netherlands..
    Cicchetti, A.
    European Space Agcy, Estec, Sci Support Off, Noordwijk, Netherlands..
    Noschese, R.
    European Space Agcy, Estec, Sci Support Off, Noordwijk, Netherlands..
    Orosei, R.
    Ist Nazl Astrofis, Ist Radioastron, Bologna, Italy..
    Annual variations in the Martian bow shock location as observed by the Mars Express mission2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 11, p. 11474-11494Article in journal (Refereed)
    Abstract [en]

    The Martian bow shock distance has previously been shown to be anticorrelated with solar wind dynamic pressure but correlated with solar extreme ultraviolet (EUV) irradiance. Since both of these solar parameters reduce with the square of the distance from the Sun, and Mars' orbit about the Sun increases by similar to 0.3 AU from perihelion to aphelion, it is not clear how the bow shock location will respond to variations in these solar parameters, if at all, throughout its orbit. In order to characterize such a response, we use more than 5 Martian years of Mars Express Analyser of Space Plasma and EneRgetic Atoms (ASPERA-3) Electron Spectrometer measurements to automatically identify 11,861 bow shock crossings. We have discovered that the bow shock distance as a function of solar longitude has a minimum of 2.39 R-M around aphelion and proceeds to a maximum of 2.65 R-M around perihelion, presenting an overall variation of similar to 11% throughout the Martian orbit. We have verified previous findings that the bow shock in southern hemisphere is on average located farther away from Mars than in the northern hemisphere. However, this hemispherical asymmetry is small (total distance variation of similar to 2.4%), and the same annual variations occur irrespective of the hemisphere. We have identified that the bow shock location is more sensitive to variations in the solar EUV irradiance than to solar wind dynamic pressure variations. We have proposed possible interaction mechanisms between the solar EUV flux and Martian plasma environment that could explain this annual variation in bow shock location.

  • 28.
    Johansson, Fredrik L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Paulsson, J. J. P.
    Univ Oslo, Dept Phys, Sem Saelands Vei 24,Postbox 1048, N-0317 Oslo, Norway.
    Harang, S. S.
    Univ Oslo, Dept Phys, Sem Saelands Vei 24,Postbox 1048, N-0317 Oslo, Norway.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mannel, T.
    Austrian Acad Sci, Space Res Inst, Schmiedlstr 6, A-8042 Graz, Austria;Karl Franzens Univ Graz, Phys Inst, Univ Pl 5, A-8010 Graz, Austria.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Miloch, W. J.
    Univ Oslo, Dept Phys, Sem Saelands Vei 24,Postbox 1048, N-0317 Oslo, Norway.
    Wedlund, C. Simon
    Univ Oslo, Dept Phys, Sem Saelands Vei 24,Postbox 1048, N-0317 Oslo, Norway.
    Thiemann, E.
    Univ Colorado, Lab Atmospher & Space Phys, 3665 Discovery Dr, Boulder, CO 80303 USA.
    Eparvier, F.
    Univ Colorado, Lab Atmospher & Space Phys, 3665 Discovery Dr, Boulder, CO 80303 USA.
    Andersson, L.
    Univ Colorado, Lab Atmospher & Space Phys, 3665 Discovery Dr, Boulder, CO 80303 USA.
    Rosetta photoelectron emission and solar ultraviolet flux at comet 67P2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, p. S626-S635Article in journal (Refereed)
    Abstract [en]

    The Langmuir Probe instrument on Rosetta monitored the photoelectron emission current of the probes during the Rosetta mission at comet 67P/Churyumov-Gerasimenko, in essence acting as a photodiode monitoring the solar ultraviolet radiation at wavelengths below 250 nm. We have used three methods of extracting the photoelectron saturation current from the Langmuir probe measurements. The resulting data set can be used as an index of the solar far and extreme ultraviolet at the Rosetta spacecraft position, including flares, in wavelengths which are important for photoionization of the cometary neutral gas. Comparing the photoemission current to data measurements by MAVEN/EUVM and TIMED/SEE, we find good correlation when 67P was at large heliocentric distances early and late in the mission, but up to 50 per cent decrease of the expected photoelectron current at perihelion. We discuss possible reasons for the photoemission decrease, including scattering and absorption by nanograins created by disintegration of cometary dust far away from the nucleus.

  • 29. Luhmann, J. G.
    et al.
    Ulusen, D.
    Ledvina, S. A.
    Mandt, K.
    Magee, B.
    Waite, J. H.
    Westlake, J.
    Cravens, T. E.
    Robertson, I.
    Edberg, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ma, Y. -J
    Wei, H.
    Russell, C. T.
    Dougherty, M. K.
    Investigating magnetospheric interaction effects on Titan's ionosphere with the Cassini orbiter Ion Neutral Mass Spectrometer, Langmuir Probe and magnetometer observations during targeted flybys2012In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 219, no 2, p. 534-555Article in journal (Refereed)
    Abstract [en]

    In the similar to 6 years since the Cassini spacecraft went into orbit around Saturn in 2004, roughly a dozen Titan flybys have occurred for which the Ion Neutral Mass Spectrometer (INMS) measured that moon's ionospheric density and composition. For these, and for the majority of the similar to 60 close flybys probing to altitudes down to similar to 950 km, Langmuir Probe electron densities were also obtained. These were all complemented by Cassini magnetometer observations of the magnetic fields affected by the Titan plasma interaction. Titan's ionosphere was expected to differ from those of other unmagnetized planetary bodies because of significant contributions from particle impact due to its magnetospheric environment. However, previous analyses of these data clearly showed the dominance of the solar photon source, with the possible exception of the nightside. This paper describes the collected ionospheric data obtained in the period between Cassini's Saturn Orbit Insertion in 2004 and 2009, and examines some of their basic characteristics with the goal of searching for magnetospheric influences. These influences might include effects on the altitude profiles of impact ionization by magnetospheric particles at the Titan orbit location, or by locally produced pickup ions freshly created in Titan's upper atmosphere. The effects of forces on the ionosphere associated with both the draped and penetrating external magnetic fields might also be discernable. A number of challenges arise in such investigations given both the observed order of magnitude variations in the magnetospheric particle sources and the unsteadiness of the magnetospheric magnetic field and plasma flows at Titan's (similar to 20Rs (Saturn Radius)) orbit. Transterminator flow of ionospheric plasma from the dayside may also supply some of the nightside ionosphere, complicating determination of the magnetospheric contribution. Moreover, we are limited by the sparse sampling of the ionosphere during the mission as the Titan interaction also depends on Saturn Local Time as well as possible intrinsic asymmetries and variations of Titan's neutral atmosphere. We use organizations of the data by key coordinate systems of the plasma interaction with Titan's ionosphere to help interpret the observations. The present analysis does not find clear characteristics of the magnetosphere's role in defining Titan's ionosphere. The observations confirm the presence of an ionosphere produced mainly by sunlight, and an absence of expected ionospheric field signatures in the data. Further investigation of the latter, in particular, may benefit from numerical experiments on the inner boundary conditions of 3D models including the plasma interaction and features such as neutral winds.

  • 30.
    Mandt, K. E.
    et al.
    Southwest Res Inst, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78228 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Koenders, C.
    Tech Univ Carolo Wilhelmina Braunschweig, D-38106 Braunschweig, Germany..
    Broiles, T.
    Southwest Res Inst, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Fuselier, S. A.
    Southwest Res Inst, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78228 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Henri, P.
    Lab Phys & Chim Environm & Espace, F-45071 Orleans 2, France..
    Nemeth, Z.
    Wigner Res Ctr Phys, H-1121 Budapest, Hungary..
    Alho, M.
    Aalto Univ, RAD ELEC, Dept Radio Sci & Engn, FI-00076 Aalto, Finland..
    Biver, N.
    Observ Paris, Sect Meudon, Lab Etud Spatiales & Instrumentat Astrophy, 5 Pl Jules Janssen, F-92196 Meudon, France..
    Beth, A.
    Imperial Coll London, London SW7 2AZ, England..
    Burch, J.
    Southwest Res Inst, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Carr, C.
    Imperial Coll London, London SW7 2AZ, England..
    Chae, K.
    Southwest Res Inst, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Coates, A. J.
    Univ Coll London, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England..
    Cupido, E.
    Imperial Coll London, London SW7 2AZ, England..
    Galand, M.
    Imperial Coll London, London SW7 2AZ, England..
    Glassmeier, K. -H
    Goetz, C.
    Tech Univ Carolo Wilhelmina Braunschweig, D-38106 Braunschweig, Germany..
    Goldstein, R.
    Southwest Res Inst, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Hansen, K. C.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Haiducek, J.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Kallio, E.
    Aalto Univ, RAD ELEC, Dept Radio Sci & Engn, FI-00076 Aalto, Finland..
    Lebreton, J. -P
    Luspay-Kuti, A.
    Southwest Res Inst, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Mokashi, P.
    Southwest Res Inst, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78228 USA..
    Nilsson, H.
    IRF Swedish Inst Space Phys Kiruna, SE-98128 Kiruna, Sweden..
    Opitz, A.
    Wigner Res Ctr Phys, H-1121 Budapest, Hungary..
    Richter, I.
    Tech Univ Carolo Wilhelmina Braunschweig, D-38106 Braunschweig, Germany..
    Samara, M.
    NASA, GSFC, Greenbelt, MD 20771 USA..
    Szego, K.
    Wigner Res Ctr Phys, H-1121 Budapest, Hungary..
    Tzou, C. -Y
    Volwerk, M.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Wedlund, C. Simon
    Univ Oslo, Dept Phys, POB 1048 Blindern, N-0316 Oslo, Norway..
    Wieser, G. Stenberg
    IRF Swedish Inst Space Phys Kiruna, SE-98128 Kiruna, Sweden..
    RPC observation of the development and evolution of plasma interaction boundaries at 67P/Churyumov-Gerasimenko2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, p. S9-S22Article in journal (Refereed)
    Abstract [en]

    One of the primary objectives of the Rosetta Plasma Consortium, a suite of five plasma instruments on-board the Rosetta spacecraft, is to observe the formation and evolution of plasma interaction regions at the comet 67P/Churyumov-Gerasimenko (67P/CG). Observations made between 2015 April and 2016 February show that solar wind-cometary plasma interaction boundaries and regions formed around 2015 mid-April and lasted through early 2016 January. At least two regions were observed, separated by an ion-neutral collisionopause boundary. The inner region was located on the nucleus side of the boundary and was characterized by low-energy water-group ions, reduced magnetic field pileup and enhanced electron densities. The outer region was located outside of the boundary and was characterized by reduced electron densities, water-group ions that are accelerated to energies above 100 eV and enhanced magnetic field pileup compared to the inner region. The boundary discussed here is outside of the diamagnetic cavity and shows characteristics similar to observations made on-board the Giotto spacecraft in the ion pileup region at 1P/Halley. We find that the boundary is likely to be related to ion-neutral collisions and that its location is influenced by variability in the neutral density and the solar wind dynamic pressure.

  • 31. Mandt, Kathleen E.
    et al.
    Gell, David A.
    Perry, Mark
    Waite, J. Hunter, Jr.
    Crary, Frank A.
    Young, David
    Magee, Brian A.
    Westlake, Joseph H.
    Cravens, Thomas
    Kasprzak, Wayne
    Miller, Greg
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Heays, Alan N.
    Lewis, Brenton R.
    Gibson, Stephen T.
    de la Haye, V.
    Liang, Mao-Chang
    Ion densities and composition of Titan's upper atmosphere derived from the Cassini Ion Neutral Mass Spectrometer: Analysis methods and comparison of measured ion densities to photochemical model simulations2012In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, p. E10006-Article in journal (Refereed)
    Abstract [en]

    The Cassini Ion Neutral Mass Spectrometer (INMS) has measured both neutral and ion species in Titan's upper atmosphere and ionosphere and the Enceladus plumes. Ion densities derived from INMS measurements are essential data for constraining photochemical models of Titan's ionosphere. The objective of this paper is to present an optimized method for converting raw data measured by INMS to ion densities. To do this, we conduct a detailed analysis of ground and in-flight calibration to constrain the instrument response to ion energy, the critical parameter on which the calibration is based. Data taken by the Cassini Radio Plasma Wave Science Langmuir Probe and the Cassini Plasma Spectrometer Ion Beam Spectrometer are used as independent measurement constraints in this analysis. Total ion densities derived with this method show good agreement with these data sets in the altitude region (similar to 1100-1400 km) where ion drift velocities are low and the mass of the ions is within the measurement range of the INMS (1-99 Daltons). Although ion densities calculated by the method presented here differ slightly from those presented in previous INMS publications, we find that the implications for the science presented in previous publications is mostly negligible. We demonstrate the role of the INMS ion densities in constraining photochemical models and find that (1) cross sections having high resolution as a function of wavelength are necessary for calculating the initial photoionization products and (2) there are disagreements between the measured ion densities representative of the initial steps in Titan photochemistry that require further investigation.

  • 32.
    Morooka, Michiko
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Hadid, Lina Z.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Persoon, A. M.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Kurth, W. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Farrell, W. M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Waite, J. H.
    Southwest Res Inst, San Antonio, TX USA.
    Perryman, R. S.
    Southwest Res Inst, San Antonio, TX USA.
    Perry, M.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA.
    Saturn's Dusty Ionosphere2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 3, p. 1679-1697Article in journal (Refereed)
    Abstract [en]

    Measurements of electrons and ions in Saturn's ionosphere down to 1,500-km altitudes as well as the ring crossing region above the ionosphere obtained by the Langmuir probe onboard the Cassini spacecraft are presented. Five nearly identical deep ionosphere flybys during the Grand Finale orbits and the Final plunge orbit revealed a rapid increase in the plasma densities and discrepancies between the electrons and ions densities (N-e and N-i) near the closest approach. The small N-e/N-i ratio indicates the presence of a dusty plasma, a plasma which charge carrier is dominated by negatively charged heavy particles. Comparison of the Langmuir probe obtained density with the light ion density obtained by the Ion and Neutral Mass Spectrometer confirmed the presence of heavy ions. An unexpected positive floating potential of the probe was also observed when N-e/N-i << 1. This suggests that Saturn's ionosphere near the density peak is in a dusty plasma state consisting of negatively and positively charged heavy cluster ions. The electron temperature (T-e) characteristics in the ionosphere are also investigated and unexpectedly high electron temperature value, up to 5000 K, has been observed below 2,500-km altitude in a region where electron-neutral collisions should be prominent. A well-defined relationship between T-e and N-e/N-i ratio was found, implying that the electron heating at low altitudes is related to the dusty plasma state of the ionosphere.

  • 33. Nilsson, H.
    et al.
    Stenberg, G.
    Futaana, Y.
    Holmstrom, M.
    Barabash, S.
    Lundin, R.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fedorov, A.
    Ion distributions in the vicinity of Mars: Signatures of heating and acceleration processes2012In: Earth Planets and Space, ISSN 1343-8832, E-ISSN 1880-5981, Vol. 64, no 2, p. 135-148Article in journal (Refereed)
    Abstract [en]

    More than three years of data from the ASPERA-3 instrument on-board Mars Express has been used to compile average distribution functions of ions in and around the Mars induced magnetosphere. We present samples of average distribution functions, as well as average flux patterns based on the average distribution functions, all suitable for detailed comparison with models of the near-Mars space environment. The average heavy ion distributions close to the planet form thermal populations with a temperature of 3 to 10 eV. The distribution functions in the tail consist of two populations, one cold which is an extension of the low altitude population, and one accelerated population of ionospheric origin ions. All significant fluxes of heavy ions in the tail are tailward. The heavy ions in the magnetosheath form a plume with the flow aligned with the bow shock, and a more radial flow direction than the solar wind origin flow. Summarizing the escape processes, ionospheric ions are heated close to the planet, presumably through wave-particle interaction. These heated populations are accelerated in the tailward direction in a restricted region. Another significant escape path is through the magnetosheath. A part of the ionospheric population is likely accelerated in the radial direction, out into the magnetosheath, although pick up of an oxygen exosphere may also be a viable source for this escape. Increased energy input from the solar wind during CIR events appear to mainly increase the number flux of escaping particles, the average energy of the escaping particles is not strongly affected. Heavy ions on the dayside may precipitate and cause sputtering of the atmosphere, though fluxes are likely lower than 0.4 x 10(23) s(-1).

  • 34.
    Nilsson, H.
    et al.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden.;Lulea Univ Technol, Dept Comp Sci Elect & Space Engn, S-98128 Kiruna, Sweden..
    Wieser, G. Stenberg
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Behar, E.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden.;Lulea Univ Technol, Dept Comp Sci Elect & Space Engn, S-98128 Kiruna, Sweden..
    Wedlund, C. Simon
    Aalto Univ, Sch Elect Engn, Dept Radio Sci & Engn, Aalto 00076, Finland..
    Kallio, E.
    Aalto Univ, Sch Elect Engn, Dept Radio Sci & Engn, Aalto 00076, Finland..
    Gunell, H.
    Belgian Inst Space Aeron, B-1180 Brussels, Belgium..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders. I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Yamauchi, M.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Koenders, C.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany..
    Wieser, M.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Lundin, R.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Barabash, S.
    Swedish Inst Space Phys, S-98128 Kiruna, Sweden..
    Mandt, K.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Goldstein, R.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Mokashi, P.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Carr, C.
    Univ London Imperial Coll Sci Technol & Med, London SW7 2AZ, England..
    Cupido, E.
    Univ London Imperial Coll Sci Technol & Med, London SW7 2AZ, England..
    Fox, P. T.
    Univ London Imperial Coll Sci Technol & Med, London SW7 2AZ, England..
    Szego, K.
    Wigner Res Ctr Phys, H-1121 Budapest, Hungary..
    Nemeth, Z.
    Wigner Res Ctr Phys, H-1121 Budapest, Hungary..
    Fedorovn, A.
    Inst Rech Astrophys & Planetol, F-31028 Toulouse, France..
    Sauvaud, J. -A
    Koskinen, H.
    Univ Helsinki, Dept Phys, Helsinki 00014, Finland.;Finnish Meteorol Inst, FIN-00101 Helsinki, Finland..
    Richter, I.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany..
    Lebreton, J. -P
    Henri, P.
    Univ Orleans, UMR CNRS 7328, Lab Phys & Chim Environm & Espace LPC2E, F-45067 Orleans, France..
    Volwerk, M.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Vallat, C.
    European Space Astron Ctr, Rosetta Sci Ground Segment, SRE OOR, Off A006, Madrid, Spain..
    Geiger, B.
    European Space Astron Ctr, Rosetta Sci Ground Segment, SRE OOR, Off A006, Madrid, Spain..
    Evolution of the ion environment of comet 67P/Churyumov-Gerasimenko2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, article id A20Article in journal (Refereed)
    Abstract [en]

    Context. The Rosetta spacecraft is escorting comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 AU, where the comet activity was low, until perihelion at 1.24 AU. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation. Aims. Using the Rosetta Plasma Consortium Ion Composition Analyzer (RPC-ICA), we study the gradual evolution of the comet ion environment, from the first detectable traces of water ions to the stage where cometary water ions accelerated to about 1 keV energy are abundant. We compare ion fluxes of solar wind and cometary origin. Methods. RPC-ICA is an ion mass spectrometer measuring ions of solar wind and cometary origins in the 10 eV-40 keV energy range. Results. We show how the flux of accelerated water ions with energies above 120 eV increases between 3.6 and 2.0 AU. The 24 h average increases by 4 orders of magnitude, mainly because high-flux periods become more common. The water ion energy spectra also become broader with time. This may indicate a larger and more uniform source region. At 2.0 AU the accelerated water ion flux is frequently of the same order as the solar wind proton flux. Water ions of 120 eV-few keV energy may thus constitute a significant part of the ions sputtering the nucleus surface. The ion density and mass in the comet vicinity is dominated by ions of cometary origin. The solar wind is deflected and the energy spectra broadened compared to an undisturbed solar wind. Conclusions. The flux of accelerated water ions moving from the upstream direction back toward the nucleus is a strongly nonlinear function of the heliocentric distance.

  • 35. Nilsson, Hans
    et al.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Stenberg, Gabriella
    Barabash, Stas
    Holmström, Mats
    Futaana, Yoshifumi
    Lundin, Rickard
    Fedorov, Andrei
    Heavy ion escape from Mars, influence from solar wind conditions and crustal magnetic fields2011In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 215, no 2, p. 475-484Article in journal (Refereed)
    Abstract [en]

    We have used more than 4 years of Mars Express ion data to estimate the escape of heavy ions (O(1)(+) O(2)(+) and CO(2)(+)) from Mars. To take the limited field of view of the instrument into account, the data has been binned into spatial bins and angular bins to create average distribution functions for different positions in the near Mars space. The net escape flux for the studied low solar activity period, between May 2007 and May 2011, is 2.0 +/- 0.2 x 10(24) s(-1). The escape has been calculated independently for four different quadrants in the Y(MSO) - Zmso plane, south, dusk, north and dawn. Escape is highest from the northern and dusk quadrants, 0.6 +/- 0.1 x 10(24) s(-1), and smallest from the south and dawn quadrants, 0.4 +/- 0.1 x 10(24) s(-1). The flux ratio of molecular (O(2)(+) and CO(2)())(+) to 0 ions is 0.9 +/- 0.1, averaged over all quadrants. The flux difference between the north and south quadrants is statistically significant, and is presumed to be due to the presence of significant crustal magnetic fields in the southern hemisphere, reducing the outflow. The difference between the dawn and dusk quadrants is likely due to the magnetic tension associated with the nominal Parker angle spiral, which should lead to higher average magnetic tension on the dusk side. The escape increases during periods of high solar wind flux and during times when co-rotating interaction regions (CIR) affect Mars. In the latter case the increase is a factor 2.4-2.9 as compared to average conditions.

  • 36. Nilsson, Hans
    et al.
    Wieser, Gabriella Stenberg
    Behar, Etienne
    Wedlund, Cyril Simon
    Gunell, Herbert
    Yamauchi, Masatoshi
    Lundin, Rickard
    Barabash, Stas
    Wieser, Martin
    Carr, Chris
    Cupido, Emanuele
    Burch, James L.
    Fedorov, Andrei
    Sauvaud, Jean-Andre
    Koskinen, Hannu
    Kallio, Esa
    Lebreton, Jean-Pierre
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Goldstein, Raymond
    Henri, Pierre
    Koenders, Christoph
    Mokashi, Prachet
    Nemeth, Zoltan
    Richter, Ingo
    Szego, Karoly
    Volwerk, Martin
    Vallat, Claire
    Rubin, Martin
    Birth of a comet magnetosphere: A spring of water ions2015In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 347, no 6220, article id UNSP aaa0571Article in journal (Refereed)
    Abstract [en]

    The Rosetta mission shall accompany comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 astronomical units through perihelion passage at 1.25 astronomical units, spanning low and maximum activity levels. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation, until the size and plasma pressure of the ionized atmosphere define its boundaries: A magnetosphere is born. Using the Rosetta Plasma Consortium ion composition analyzer, we trace the evolution from the first detection of water ions to when the atmosphere begins repelling the solar wind (similar to 3.3 astronomical units), and we report the spatial structure of this early interaction. The near-comet water population comprises accelerated ions (<800 electron volts), produced upstream of Rosetta, and lower energy locally produced ions; we estimate the fluxes of both ion species and energetic neutral atoms.

  • 37.
    Noonan, John W.
    et al.
    Southwest Res Inst, Dept Space Studies, Suite 300,1050 Walnut St, Boulder, CO 80302 USA;Univ Arizona, Lunar & Planetary Lab, 1629 E Univ Blvd, Tucson, AZ 85721 USA.
    Stern, S. Alan
    Southwest Res Inst, Dept Space Studies, Suite 300,1050 Walnut St, Boulder, CO 80302 USA.
    Feldman, Paul D.
    Johns Hopkins Univ, Dept Phys & Astron, 3400 N Charles St, Baltimore, MD 21218 USA.
    Broiles, Thomas
    Space Sci Inst, 4750 Walnut St,Suite 205, Boulder, CO 80301 USA.
    Wedlund, Cyril Simon
    Univ Oslo, Dept Phys, Box 1048 Blindern, N-0316 Oslo, Norway.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Schindhelm, Eric
    Ball Aerosp & Technol Corp, 1600 Commerce St, Boulder, CO 80301 USA.
    Parker, Joel Wm
    Southwest Res Inst, Dept Space Studies, Suite 300,1050 Walnut St, Boulder, CO 80302 USA.
    Keeney, Brian A.
    Southwest Res Inst, Dept Space Studies, Suite 300,1050 Walnut St, Boulder, CO 80302 USA.
    Vervack, Ronald J., Jr.
    Johns Hopkins Univ, Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA.
    Steffl, Andrew J.
    Southwest Res Inst, Dept Space Studies, Suite 300,1050 Walnut St, Boulder, CO 80302 USA.
    Knight, Matthew M.
    Univ Maryland, Astron Dept, College Pk, MD 20742 USA.
    Weaver, Harold A.
    Johns Hopkins Univ, Appl Phys Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA.
    Feaga, Lori M.
    Univ Maryland, Astron Dept, College Pk, MD 20742 USA.
    A'Hearn, Michael
    Univ Maryland, Astron Dept, College Pk, MD 20742 USA.
    Bertaux, Jean-Loup
    CNRS UVSQ IPSL, LATMOS, 11 Blvd Alembert, F-78280 Guyancourt, France.
    Ultraviolet Observations of Coronal Mass Ejection Impact on Comet 67P/Churyumov-Gerasimenko by Rosetta Alice2018In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 156, no 1, article id 16Article in journal (Refereed)
    Abstract [en]

    The Alice ultraviolet spectrograph on the European Space Agency Rosetta spacecraft observed comet 67P/Churyumov-Gerasimenko in its orbit around the Sun for just over two years. Alice observations taken in 2015 October, two months after perihelion, show large increases in the comet's Ly beta, OI 1304, OI 1356, and CI 1657 angstrom atomic emission that initially appeared to indicate gaseous outbursts. However, the Rosetta Plasma Consortium instruments showed a coronal mass ejection (CME) impact at the comet coincident with the emission increases, suggesting that the CME impact may have been the cause of the increased emission. The presence of the semi-forbidden OI 1356 angstrom emission multiplet is indicative of a substantial increase in dissociative electron impact emission from the coma, suggesting a change in the electron population during the CME impact. The increase in dissociative electron impact could be a result of the interaction between the CME and the coma of 67P or an outburst coincident with the arrival of the CME. The observed dissociative electron impact emission during this period is used to characterize the O-2 content of the coma at two peaks during the CME arrival. The mechanism that could cause the relationship between the CME and UV emission brightness is not well constrained, but we present several hypotheses to explain the correlation.

  • 38.
    Odelstad, Elias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Tzou, C. -Y
    Univ Bern, Phys Inst, Bern, Switzerland.
    Carr, C.
    Univ London Imperial Coll Sci Technol & Med, Space & Atmospher Phys Grp, London, England..
    Cupido, E.
    Univ London Imperial Coll Sci Technol & Med, Space & Atmospher Phys Grp, London, England..
    Evolution of the plasma environment of comet 67P from spacecraft potential measurements by the Rosetta Langmuir probe instrument2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 23Article in journal (Refereed)
    Abstract [en]

    We study the evolution of the plasma environment of comet 67P using measurements of the spacecraft potential from early September 2014 (heliocentric distance 3.5 AU) to late March 2015 (2.1 AU) obtained by the Langmuir probe instrument. The low collision rate keeps the electron temperature high (similar to 5 eV), resulting in a negative spacecraft potential whose magnitude depends on the electron density. This potential is more negative in the northern (summer) hemisphere, particularly over sunlit parts of the neck region on the nucleus, consistent with neutral gas measurements by the Cometary Pressure Sensor of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis. Assuming constant electron temperature, the spacecraft potential traces the electron density. This increases as the comet approaches the Sun, most clearly in the southern hemisphere by a factor possibly as high as 20-44 between September 2014 and January 2015. The northern hemisphere plasma density increase stays around or below a factor of 8-12, consistent with seasonal insolation change.

  • 39.
    Omidi, N.
    et al.
    Solana Sci Inc, Solana Beach, CA 92075 USA..
    Sulaiman, A. H.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Kurth, W.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Madanian, H.
    Univ Kansas, Dept Phys, Lawrence, KS 66045 USA..
    Cravens, T.
    Univ Kansas, Dept Phys, Lawrence, KS 66045 USA..
    Sergis, N.
    Acad Athens, Off Space Res & Technol, Athens, Greece.;Natl Observ Athens, Inst Astron Astrophys Space Applicat & Remote Sen, Athens, Greece..
    Dougherty, M. K.
    Imperial Coll London, Blackett Lab, London, England..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    A Single Deformed Bow Shock for Titan-Saturn System2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 11, p. 11058-11075Article in journal (Refereed)
    Abstract [en]

    During periods of high solar wind pressure, Saturn's bow shock is pushed inside Titan's orbit exposing the moon and its ionosphere to the solar wind. The Cassini spacecraft's T96 encounter with Titan occurred during such a period and showed evidence for shocks associated with Saturn and Titan. It also revealed the presence of two foreshocks: one prior to the closest approach (foreshock 1) and one after (foreshock 2). Using electromagnetic hybrid (kinetic ions and fluid electrons) simulations and Cassini observations, we show that the origin of foreshock 1 is tied to the formation of a single deformed bow shock for the Titan-Saturn system. We also report the observations of a structure in foreshock 1 with properties consistent with those of spontaneous hot flow anomalies formed in the simulations and previously observed at Earth, Venus, and Mars. The results of hybrid simulations also show the generation of oblique fast magnetosonic waves upstream of the outbound Titan bow shock in agreement with the observations of large-amplitude magnetosonic pulsations in foreshock 2. We also discuss the implications of a single deformed bow shock for new particle acceleration mechanisms and also Saturn's magnetopause and magnetosphere.

  • 40. Richard, M. S.
    et al.
    Cravens, T. E.
    Wylie, C.
    Webb, D.
    Chediak, Q.
    Perryman, R.
    Mandt, K.
    Westlake, J.
    Waite, J. H., Jr.
    Robertson, I.
    Magee, B. A.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    An empirical approach to modeling ion production rates in Titan's ionosphere I: Ion production rates on the dayside and globally2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 2, p. 1264-1280Article in journal (Refereed)
    Abstract [en]

    Titan's ionosphere is created when solar photons, energetic magnetospheric electrons or ions, and cosmic rays ionize the neutral atmosphere. Electron densities generated by current theoretical models are much larger than densities measured by instruments on board the Cassini orbiter. This model density overabundance must result either from overproduction or from insufficient loss of ions. This is the first of two papers that examines ion production rates in Titan's ionosphere, for the dayside and nightside ionosphere, respectively. The first (current) paper focuses on dayside ion production rates which are computed using solar ionization sources (photoionization and electron impact ionization by photoelectrons) between 1000 and 1400km. In addition to theoretical ion production rates, empirical ion production rates are derived from CH4, CH3+, and CH4+ densities measured by the INMS (Ion Neutral Mass Spectrometer) for many Titan passes. The modeled and empirical production rate profiles from measured densities of N-2(+) and CH4+ are found to be in good agreement (to within 20%) for solar zenith angles between 15 and 90 degrees. This suggests that the overabundance of electrons in theoretical models of Titan's dayside ionosphere is not due to overproduction but to insufficient ion losses.

  • 41. Romanelli, N.
    et al.
    Modolo, R.
    Dubinin, E.
    Berthelier, J. -J
    Bertucci, C.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Leblanc, F.
    Canu, P.
    Edberg, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Waite, H.
    Kurth, W. S.
    Gurnett, D.
    Coates, A.
    Dougherty, M.
    Outflow and plasma acceleration in Titan's induced magnetotail: Evidence of magnetic tension forces2014In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 119, no 12Article in journal (Refereed)
    Abstract [en]

    Cassini plasma wave and particle observations are combined with magnetometer measurements to study Titan's induced magnetic tail. In this study, we report and analyze the plasma acceleration in Titan's induced magnetotail observed in flybys T17, T19, and T40. Radio and Plasma Wave Science observations show regions of cold plasma with electron densities between 0.1 and a few tens of electrons per cubic centimeter. The Cassini Plasma Spectrometer (CAPS)-ion mass spectrometer (IMS) measurements suggest that ionospheric plasma in this region is composed of ions with masses ranging from 15 to 17 amu and from 28 to 31 amu. From these measurements, we determine the bulk velocity of the plasma and the Alfven velocity in Titan's tail region. Finally, a Walen test of such measurements suggest that the progressive acceleration of the ionospheric plasma shown by CAPS can be interpreted in terms of magnetic tension forces.

  • 42.
    Shebanits, Oleg
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cui, Jun
    School of Atmospheric Sciences, Sun Yat-Sen University, China.
    Mandt, Kathleen
    Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas, USA.; Space Science and Engineering Division, Southwest Research Institute, San Antonio, TX, USA..
    Waite, Hunter
    Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas, USA.
    Photoionization modeling of Titan’s dayside ionosphere2017In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 850, no 2, article id L26Article in journal (Refereed)
    Abstract [en]

    Previous modeling studies of Titan’s dayside ionosphere predicts electron numberdensities roughly a factor of 2 higher than observed by the RPWS/Langmuir probe. The issuecan equivalently be described as that the ratio between the calculated electron productionrates and the square of the observed electron number densities result in roughly a factor of4 higher effective recombination coefficient than expected from the ion composition and theelectron temperature. Here we make an extended reassessment of Titan’s dayside ionizationbalance focusing on 34 flybys between TA and T120. Using a re-calibrated dataset and bytaking the presence of negative ions into account we arrive at lower effective recombinationcoefficients compared with earlier studies. The values are still higher than expected from theion composition and the electron temperature, but by a factor of ~2 − 3 instead of a factorof ~4. We have also investigated whether the derived effective recombination coefficientsdisplay dependencies on parameters such as the solar zenith angle, the integrated solar EUVintensity (< 80 nm) and the corotational plasma ram direction and found statisticallysignificant trends which may be explained by a declining photoionization against thebackground ionization by magnetospheric particles (SZA, RAM) and altered photochemistry(EUV). We find that a series of flybys that occurred during solar minimum (2008) and withsimilar flyby geometries are associated with enhanced values of the effective recombinationcoefficient compared with the remaining dataset, which also suggests a chemistry dependenton the sunlight conditions.

  • 43.
    Shebanits, Oleg
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Holmberg, Mika
    Université de Toulouse, UPS-OMP, IRAP, Toulouse, France.; CNRS, IRAP, Toulouse, France.
    Morooka, Michiko
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mandt, Kathleen
    Waite, Hunter
    Titan’s ionosphere: A survey of solar EUV influences2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 7, p. 7491-7503Article in journal (Refereed)
    Abstract [en]

    Effects of solar EUV on positive ions and heavy negative charge carriers (molecular ions, aerosol, and/or dust) in Titan’s ionosphere are studied over the course of almost 12 years, including 78 flybys below 1400 km altitude between TA (October 2004) and T120 (June 2016). The Radio and Plasma Wave Science/Langmuir Probe-measured ion charge densities (normalized by the solar zenith angle) show statistically significant variations with respect to the solar EUV flux. Dayside charge densities increase by a factor of ≈2 from solar minimum to maximum, while nightside charge densities are found to anticorrelate with the EUV flux and decrease by a factor of ≈3–4. The overall EUV dependence of the ion charge densities suggest inapplicability of the idealized Chapman theory below 1200 km in Titan’s ionosphere. Nightside charge densities are also found to vary along Titan’s orbit, with higher values in the sunward magnetosphere of Saturn compared to the magnetotail.

  • 44.
    Shebanits, Oleg
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, J. -E
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Crary, F. J.
    Univ Colorado Boulder, Boulder, CO USA..
    Wellbrock, A.
    UCL, Mullard Space Sci Lab, London, England.;Univ London Birkbeck Coll, Ctr Planetary Sci, London, England..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Desai, R. T.
    UCL, Mullard Space Sci Lab, London, England.;Univ London Birkbeck Coll, Ctr Planetary Sci, London, England..
    Coates, A. J.
    UCL, Mullard Space Sci Lab, London, England.;Univ London Birkbeck Coll, Ctr Planetary Sci, London, England..
    Mandt, K. E.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX USA..
    Waite, J. H., Jr.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA..
    Ion and aerosol precursor densities in Titan's ionosphere: A multi-instrument case study2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 10, p. 10075-10090Article in journal (Refereed)
    Abstract [en]

    The importance of the heavy ions and dust grains for the chemistry and aerosol formation in Titan's ionosphere has been well established in the recent years of the Cassini mission. In this study we combine independent in situ plasma (Radio Plasma and Wave Science Langmuir Probe (RPWS/LP)) and particle (Cassini Plasma Science Electron Spectrometer, Cassini Plasma Science Ion Beam Spectrometer, and Ion and Neutral Mass Spectrometer) measurements of Titan's ionosphere for selected flybys (T16, T29, T40, and T56) to produce altitude profiles of mean ion masses including heavy ions and develop a Titan-specific method for detailed analysis of the RPWS/LP measurements (applicable to all flybys) to further constrain ion charge densities and produce the first empirical estimate of the average charge of negative ions and/or dust grains. Our results reveal the presence of an ion-ion (dusty) plasma below similar to 1100 km altitude, with charge densities exceeding the primary ionization peak densities by a factor >= 2 in the terminator and nightside ionosphere (n(e)/n(i) <= 0.1). We suggest that ion-ion (dusty) plasma may also be present in the dayside ionosphere below 900 km (n(e)/n(i) < 0.5 at 1000 km altitude). The average charge of the dust grains (>= 1000 amu) is estimated to be between -2.5 and -1.5 elementary charges, increasing toward lower altitudes.

  • 45.
    Shebanits, Oleg
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mandt, K.
    Ågren, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Waite, J. H., Jr.
    Negative ion densities in the ionosphere of Titan-Cassini RPWS/LP results2013In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 84, p. 153-162Article in journal (Refereed)
    Abstract [en]

    The Cassini spacecraft Radio and Plasma Wave Science (RPWS) Langmuir Probe (LP) provides in-situ measurements of Titan's ionosphere. We present here data from 47 deep flybys in the time period October 2004 July 2012 of charge densities of positive and negative ions as well as electrons. These densities have been mapped with respect to altitude and solar zenith angle (SZA) in an altitude range of 880-1400 km. The inferred electron number densities are consistent with earlier presented observational results. Negative ion charge densities exhibit a trend that exponentially increases towards lower altitudes within the covered altitude range. This is especially evident on the nightside of Titan (SZA > 110 degrees). The negative ion charge densities at the lowest traversed altitudes (near 960 km) are inferred to be in the range 300-2500 cm(-3). The results show that very few free electrons (n(e)/n(i)similar to 0.1-0.7) exist in the deepest regions (880-1050 km) of Titan's nightside ionosphere. Instead the deep nightside part of Titan's ionosphere is dominated by both negatively and positively charged heavy (> 100 amu) organic ions. We therefore believe a dust/aerosol-ion plasma exists here, similar to what is found in noctilucent clouds in Earth's mesosphere. 

  • 46.
    Snodgrass, C.
    et al.
    Open Univ, Sch Phys Sci, Milton Keynes MK7 6AA, Bucks, England..
    A'Hearn, M. F.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Aceituno, F.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Afanasiev, V.
    Russian Acad Sci, Special Astrophys Observ, Nizhnii Arkhyz, Russia..
    Bagnulo, S.
    Armagh Observ, Coll Hill, Armagh BT61 9DG, North Ireland..
    Bauer, J.
    Jet Prop Lab, M-S 183-401,4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Bergond, G.
    CSIC MPG, Ctr Astron Hispano Aleman, Gergal 04550, Spain..
    Besse, S.
    ESA ESAC, POB 78, Villanueva La Canada 28691, Spain..
    Biver, N.
    Univ Paris Diderot, LESIA, Observ Paris, CNRS,UPMC Univ Paris 06, 5 Pl J Janssen, F-92195 Meudon, France..
    Bodewits, D.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Boehnhardt, H.
    Max Planck Inst Sonnensystforsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Bonev, B. P.
    Amer Univ, Dept Phys, 4400 Massachusetts Ave NW, Washington, DC 20016 USA..
    Borisov, G.
    Armagh Observ, Coll Hill, Armagh BT61 9DG, North Ireland.;Inst Astron, 72 Tsarigradsko Chaussee Blvd, BG-1784 Sofia, Bulgaria.;Natl Astron Observ, 72 Tsarigradsko Chaussee Blvd, BG-1784 Sofia, Bulgaria..
    Carry, B.
    Univ Cote Azur, Observ Cote Azur, CNRS, Lagrange, France.;Univ Lille, CNRS, IMCCE, Observ Paris,PSL Res Univ,Sorbonne Univ,UPMC Univ, Lille, France..
    Casanova, V.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Cochran, A.
    Armagh Observ, Coll Hill, Armagh BT61 9DG, North Ireland.;Univ Texas Austin, McDonald Observ, 1 Univ Stn, Austin, TX 78712 USA.;LATMOS IPSL, 11 Bld Alembert, F-78280 Guyancourt, France..
    Conn, B. C.
    Australian Natl Univ, Res Sch Astron & Astrophys, Canberra, ACT, Australia.;Recinto AURA, Gemini Observ, Colina El Pino S-N,Casilla 603, La Serena, Chile..
    Davidsson, B.
    Jet Prop Lab, M-S 183-401,4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Davies, J. K.
    Royal Observ Edinburgh, UK Astron Technol Ctr, Blackford Hill, Edinburgh EH9 3HJ, Midlothian, Scotland..
    de Leon, J.
    IAC, C Via Lactea S-N, San Cristobal la Laguna 38205, Spain.;Univ La Laguna, Dept Astrofis, Tenerife 38206, Spain..
    de Mooij, E.
    Queens Univ, Sch Math & Phys, Astrophys Res Ctr, Belfast BT7 1NN, Antrim, North Ireland..
    de Val-Borro, M.
    Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA.;Astrochemistry Lab, NASA Goddard Space Flight Ctr, Code 6930, Greenbelt, MD 20771 USA.;Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA..
    Delacruz, M.
    Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA..
    DiSanti, M. A.
    Astrochemistry Lab, NASA Goddard Space Flight Ctr, Code 6930, Greenbelt, MD 20771 USA..
    Drew, J. E.
    Univ Hertfordshire, Sch Phys Astron & Math, Coll Lane, Hatfield AL10 9AB, Herts, England..
    Duffard, R.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Faggi, S.
    INAF, Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Feaga, L.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Fitzsimmons, A.
    Queens Univ, Sch Math & Phys, Astrophys Res Ctr, Belfast BT7 1NN, Antrim, North Ireland..
    Fujiwara, H.
    Natl Astron Observ Japan, Subaru Telescope, 650 North Aohoku Pl, Hilo, HI 96720 USA..
    Gibb, E. L.
    Univ Missouri, Dept Phys & Astron, St Louis, MO 63121 USA..
    Gillon, M.
    Univ Liege, Inst Astrophys & Gephys, Allee 6 Aout 17, B-4000 Liege, Belgium..
    Green, S. F.
    Open Univ, Sch Phys Sci, Milton Keynes MK7 6AA, Bucks, England..
    Guijarro, A.
    CSIC MPG, Ctr Astron Hispano Aleman, Gergal 04550, Spain..
    Guilbert-Lepoutre, A.
    Univ Franche Comte, UMR 6213, CNRS, Inst UTINAM, Besancon, France..
    Gutierrez, P. J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Hadamcik, E.
    CNRS INSU, 11 Bld Alembert, F-78280 Guyancourt, France.;UPMC, Sorbonne Univ, 11 Bld Alembert, F-78280 Guyancourt, France.;UVSQ, UPSay, 11 Bld Alembert, F-78280 Guyancourt, France.;LATMOS IPSL, 11 Bld Alembert, F-78280 Guyancourt, France..
    Hainaut, O.
    European Southern Observ, Karl Schwarzschild Str 2, D-85748 Garching, Germany..
    Haque, S.
    Univ West Indies, Dept Phys, St Augustine, Trinid & Tobago..
    Hedrosa, R.
    CSIC MPG, Ctr Astron Hispano Aleman, Gergal 04550, Spain..
    Hines, D.
    Space Telescope Sci Inst, 3700 San Martin Dr, Baltimore, MD 21218 USA..
    Hopp, U.
    Ludwig Maximilian Univ Munich, UnivObserv, Scheiner Str 1, D-81679 Munich, Germany..
    Hoyo, F.
    CSIC MPG, Ctr Astron Hispano Aleman, Gergal 04550, Spain..
    Hutsemekers, D.
    Univ Liege, Inst Astrophys & Gephys, Allee 6 Aout 17, B-4000 Liege, Belgium..
    Hyland, M.
    Queens Univ, Sch Math & Phys, Astrophys Res Ctr, Belfast BT7 1NN, Antrim, North Ireland..
    Ivanova, O.
    Slovak Acad Sci, Astron Inst, Tatranska Lomnica 05960, Slovakia..
    Jehin, E.
    Univ Liege, Inst Astrophys & Gephys, Allee 6 Aout 17, B-4000 Liege, Belgium..
    Jones, G. H.
    Univ Coll London, Holmbury St Mary, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Keane, J. V.
    Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA..
    Kelley, M. S. P.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Kiselev, N.
    Natl Acad Sci, Main Astron Observ, Kiev, Ukraine..
    Kleyna, J.
    Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA..
    Kluge, M.
    Ludwig Maximilian Univ Munich, UnivObserv, Scheiner Str 1, D-81679 Munich, Germany..
    Knight, M. M.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Kokotanekova, R.
    Open Univ, Sch Phys Sci, Milton Keynes MK7 6AA, Bucks, England.;Max Planck Inst Sonnensystforsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Koschny, D.
    European Space Agcy, Res & Sci Support Dept, NL-2201 Noordwijk, Netherlands..
    Kramer, E. A.
    Jet Prop Lab, M-S 183-401,4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Lopez-Moreno, J. J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Lacerda, P.
    Queens Univ, Sch Math & Phys, Astrophys Res Ctr, Belfast BT7 1NN, Antrim, North Ireland..
    Lara, L. M.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Lasue, J.
    Univ Toulouse, UPS OMP, IRAP CNRS, Toulouse, France..
    Lehto, H. J.
    Univ Turku, Dept Phys & Astron, Tuorla Observ, Vaisalantie 20, Suzhou 21500, Peoples R China..
    Levasseur-Regourd, A. C.
    UPMC, Sorbonne Univ, BC 102,4 Pl Jussieu, F-75005 Paris, France.;UVSQ, UPSay, BC 102,4 Pl Jussieu, F-75005 Paris, France.;CNRS INSU, BC 102,4 Pl Jussieu, F-75005 Paris, France.;LATMOS IPSL, BC 102,4 Pl Jussieu, F-75005 Paris, France..
    Licandro, J.
    IAC, C Via Lactea S-N, San Cristobal la Laguna 38205, Spain.;Univ La Laguna, Dept Astrofis, Tenerife 38206, Spain..
    Lin, Z. Y.
    Natl Cent Univ, Grad Inst Astron, 300 Zhongda Rd, Taoyuan 320, Taiwan..
    Lister, T.
    Las Cumbres Observ, 6740 Cortona Dr,Ste 102, Goleta, CA 93117 USA..
    Lowry, S. C.
    Univ Kent, Sch Phys Sci, Ctr Astrophys & Planetary Sci, Canterbury CT2 7NH, Kent, England..
    Mainzer, A.
    Jet Prop Lab, M-S 183-401,4800 Oak Grove Dr, Pasadena, CA 91109 USA..
    Manfroid, J.
    Univ Liege, Inst Astrophys & Gephys, Allee 6 Aout 17, B-4000 Liege, Belgium..
    Marchant, J.
    Liverpool John Moores Univ, Astrophys Res Inst, Liverpool L3 5RF, Merseyside, England..
    Mckay, A. J.
    Univ Texas Austin, McDonald Observ, 1 Univ Stn, Austin, TX 78712 USA.;Astrochemistry Lab, NASA Goddard Space Flight Ctr, Code 6930, Greenbelt, MD 20771 USA..
    McNeill, A.
    Queens Univ, Sch Math & Phys, Astrophys Res Ctr, Belfast BT7 1NN, Antrim, North Ireland..
    Meech, K. J.
    Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA..
    Micheli, M.
    ESA SSA NEO Coordinat Ctr, Frascati, Italy..
    Mohammed, I.
    Caribbean Inst Astron, St Augustine, Trinid & Tobago..
    Monguio, M.
    Univ Hertfordshire, Sch Phys Astron & Math, Coll Lane, Hatfield AL10 9AB, Herts, England..
    Moreno, F.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Munoz, O.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Mumma, M. J.
    Astrochemistry Lab, NASA Goddard Space Flight Ctr, Code 6930, Greenbelt, MD 20771 USA..
    Nikolov, P.
    Inst Astron, 72 Tsarigradsko Chaussee Blvd, BG-1784 Sofia, Bulgaria.;Natl Astron Observ, 72 Tsarigradsko Chaussee Blvd, BG-1784 Sofia, Bulgaria..
    Opitom, C.
    Univ Liege, Inst Astrophys & Gephys, Allee 6 Aout 17, B-4000 Liege, Belgium.;European Southern Observ, Alonso Cordova 3107, Santiago, Chile..
    Ortiz, J. L.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Paganini, L.
    Astrochemistry Lab, NASA Goddard Space Flight Ctr, Code 6930, Greenbelt, MD 20771 USA..
    Pajuelo, M.
    Univ Lille, CNRS, IMCCE, Observ Paris,PSL Res Univ,Sorbonne Univ,UPMC Univ, Lille, France.;Pontificia Univ Catolica Peru, Dept Ciencias, Secc Fis, Apartado 1761, Lima, Peru..
    Pozuelos, F. J.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain.;Univ Liege, Inst Astrophys & Gephys, Allee 6 Aout 17, B-4000 Liege, Belgium..
    Protopapa, S.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Pursimo, T.
    Nord Optic Telescope, Apartado 474, Santa Cruz Tenerife, CA 38700 USA..
    Rajkumar, B.
    Univ West Indies, Dept Phys, St Augustine, Trinid & Tobago..
    Ramanjooloo, Y.
    Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA..
    Ramos, E.
    CSIC MPG, Ctr Astron Hispano Aleman, Gergal 04550, Spain..
    Ries, C.
    Ludwig Maximilian Univ Munich, UnivObserv, Scheiner Str 1, D-81679 Munich, Germany..
    Riffeser, A.
    Ludwig Maximilian Univ Munich, UnivObserv, Scheiner Str 1, D-81679 Munich, Germany..
    Rosenbush, V.
    Natl Acad Sci, Main Astron Observ, Kiev, Ukraine..
    Rousselot, P.
    Univ Franche Comte, Observ Sci, Inst UTINAM, UMR CNRS 6213,Univ THETA, BP 1615, F-25010 Besancon, France..
    Ryan, E. L.
    SETI Inst, 189 Bernardo Ave Suite 200, Mountain View, CA 94043 USA..
    Santos-Sanz, P.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Schleicher, D. G.
    Lowell Observ, 1400 W Mars Hill Rd, Flagstaff, AZ 86001 USA..
    Schmidt, M.
    Ludwig Maximilian Univ Munich, UnivObserv, Scheiner Str 1, D-81679 Munich, Germany..
    Schulz, R.
    European Space Agcy, Sci Support Off, NL-2201 AZ Noordwijk, Netherlands..
    Sen, A. K.
    Assam Univ, Dept Phys, Silchar 788011, India..
    Somero, A.
    Univ Turku, Dept Phys & Astron, Tuorla Observ, Vaisalantie 20, Suzhou 21500, Peoples R China..
    Sota, A.
    CSIC, Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain..
    Stinson, A.
    Armagh Observ, Coll Hill, Armagh BT61 9DG, North Ireland..
    Sunshine, J. M.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Thompson, A.
    Queens Univ, Sch Math & Phys, Astrophys Res Ctr, Belfast BT7 1NN, Antrim, North Ireland..
    Tozzi, G. P.
    INAF, Osserv Astrofis Arcetri, Largo E Fermi 5, I-50125 Florence, Italy..
    Tubiana, C.
    Max Planck Inst Sonnensystforsch, Justus von Liebig Weg 3, D-37077 Gottingen, Germany..
    Villanueva, G. L.
    Astrochemistry Lab, NASA Goddard Space Flight Ctr, Code 6930, Greenbelt, MD 20771 USA..
    Wang, X.
    Chinese Acad Sci, Yunnan Observ, POB 110, Kunming 650011, Yunnan, Peoples R China.;Chinese Acad Sci, Key Lab Struct & Evolut Celestial Objects, Kunming 650011, Peoples R China..
    Wooden, D. H.
    NASA Ames Res Ctr, MS 245-3, Moffett Field, CA 94035 USA..
    Yagi, M.
    Natl Astron Observ, 2-21-1 Osawa, 0 Mitaka, Tokyo 1818588, Japan..
    Yang, B.
    European Southern Observ, Alonso Cordova 3107, Santiago, Chile..
    Zaprudin, B.
    Univ Turku, Dept Phys & Astron, Tuorla Observ, Vaisalantie 20, Suzhou 21500, Peoples R China..
    Zegmott, T. J.
    Univ Kent, Sch Phys Sci, Ctr Astrophys & Planetary Sci, Canterbury CT2 7NH, Kent, England..
    The 67P/Churyumov-Gerasimenko observation campaign in support of the Rosetta mission2017In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, no 2097, article id 20160249Article in journal (Refereed)
    Abstract [en]

    We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/ Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively 'well-behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends-in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies. This article is part of the themed issue 'Cometary science after Rosetta'.

  • 47. Ulusen, D.
    et al.
    Luhmann, J. G.
    Ma, Y. J.
    Mandt, K. E.
    Waite, J. H.
    Dougherty, M. K.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Russell, C. T.
    Cravens, T. E.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Comparisons of Cassini flybys of the Titan magnetospheric interaction with an MHD model: Evidence for organized behavior at high altitudes2012In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 217, no 1, p. 43-54Article in journal (Refereed)
    Abstract [en]

    Recent papers suggest the significant variability of conditions in Saturn's magnetosphere at the orbit of Titan. Because of this variability, it was expected that models would generally have a difficult time regularly comparing to data from the Titan flybys. However, we find that in contrast to this expectation, it appears that there is underlying organization of the interaction features roughly above similar to 1800 km (1.7 Rt) altitude by the average external field due to Saturn's dipole moment. In this study, we analyze Cassini's plasma and magnetic field data collected at 9 Titan encounters during which the external field is close to the ideal southward direction and compare these observations to the results from a 2-fluid (1 ion, 1 electron) 7-species MHD model simulations obtained under noon SLT conditions. Our comparative analysis shows that under noon SLT conditions the Titan plasma interaction can be viewed in two layers: an outer layer between 6400 and 1800 km where interaction features observed in the magnetic field are in basic agreement with a purely southward external field interaction and an inner layer below 1800 km where the magnetic field measurements show strong variations and deviate from the model predictions. Thus the basic features inferred from the Voyager 1 flyby seem to be generally present above similar to 1800 km in spite of the ongoing external variations from SLT excursions, time variability and magnetospheric current systems as long as a significant southward external field component is present. At around similar to 1800 km kinetic effects (such as mass loading and heavy ion pickup) and below 1800 km ionospheric effects (such as drag of ionospheric plasma due to coupling with neutral winds and/or magnetic memory of Titan's ionosphere) complicate what is observed.

  • 48.
    Vech, Daniel
    et al.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Stenberg, Gabriella
    Swedish Inst Space Phys, Kiruna, Sweden..
    Nilsson, Hans
    Swedish Inst Space Phys, Kiruna, Sweden..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Opitz, Andrea
    Wigner Res Ctr Phys, Budapest, Hungary..
    Szego, Karoly
    Wigner Res Ctr Phys, Budapest, Hungary..
    Zhang, Tielong
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Futaana, Yoshifumi
    Swedish Inst Space Phys, Kiruna, Sweden..
    Statistical features of the global polarity reversal of the Venusian induced magnetosphere in response to the polarity change in interplanetary magnetic field2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 5, p. 3951-3962Article in journal (Refereed)
    Abstract [en]

    In this study we present the first statistical analysis on the effects of heliospheric current sheet crossings on the induced magnetosphere of Venus. These events are of particular interest because they lead to the reconfiguration of the induced magnetosphere with opposite polarity. We use a statistical approach based on 117 orbit pairs, and we study the spatial distribution of the heavy ion flux measurements in the plasma environment of Venus. The average and median heavy ion flux measurements are compared before and after the polarity reversal events. The results show that after the events the average and median heavy ion fluxes in the magnetotail are reduced by the factors of 0.750.09 and 0.52, respectively. We find that even if a passage of a current sheet is a short time scale event lasting about 10min, its effect on the near-Venus plasma environment lasts for a few hours. We conclude that the observations show similarities to the previous comet studies and the polarity reversal of the induced magnetosphere might be accompanied with dayside reconnection and magnetic disconnection of the plasma tail from the planetary ionosphere.

  • 49.
    Vigren, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Altwegg, K.
    Univ Bern, Inst Phys, Bern, Switzerland..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders. I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Galand, M.
    Imperial Coll London, Dept Phys, London, England..
    Henri, P.
    Lab Phys & Chim Environm & Espace, Orleans, France..
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. Lab Phys & Chim Environm & Espace, Orleans, France..
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Tzou, C. -Y
    Vallieres, X.
    Lab Phys & Chim Environm & Espace, Orleans, France..
    Model-Observation Comparisons Of Electron Number Densities In The Coma Of 67P/Churyumov-Gerasimenko During 2015 January2016In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 152, no 3, article id 59Article in journal (Refereed)
    Abstract [en]

    During 2015 January 9-11, at a heliocentric distance of similar to 2.58-2.57 au, the ESA Rosetta spacecraft resided at a cometocentric distance of similar to 28 km from the nucleus of comet 67P/Churyumov-Gerasimenko, sweeping the terminator at northern latitudes of 43 degrees N-58 degrees N. Measurements by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Comet Pressure Sensor (ROSINA/COPS) provided neutral number densities. We have computed modeled electron number densities using the neutral number densities as input into a Field Free Chemistry Free model, assuming H2O dominance and ion-electron pair formation by photoionization only. A good agreement (typically within 25%) is found between the modeled electron number densities and those observed from measurements by the Mutual Impedance Probe (RPC/MIP) and the Langmuir Probe (RPC/LAP), both being subsystems of the Rosetta Plasma Consortium. This indicates that ions along the nucleus-spacecraft line were strongly coupled to the neutrals, moving radially outward with about the same speed. Such a statement, we propose, can be further tested by observations of H3O+/H2O+ number density ratios and associated comparisons with model results.

  • 50.
    Vigren, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Engelhardt, Ilka. A. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Galand, M.
    Imperial Coll London, Dept Phys, London SW7 2AZ, England.
    Goetz, C.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, D-38106 Braunschweig, Germany.
    Henri, P.
    Lab Phys & Chim Environm & Espace, F-45071 Orleans 2, France.
    Heritier, K.
    Imperial Coll London, Dept Phys, London SW7 2AZ, England.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Nilsson, H.
    Swedish Inst Space Phys Kiruna, SE-98128 Kiruna, Sweden.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Rubin, M.
    Univ Bern, Inst Phys, CH-3012 Bern, Switzerland.
    Stenberg-Wieser, G.
    Swedish Inst Space Phys Kiruna, SE-98128 Kiruna, Sweden.
    Tzou, C. -Y
    Vallieres, X.
    Lab Phys & Chim Environm & Espace, F-45071 Orleans 2, France.
    Effective ion speeds at similar to 200-250 km from comet 67P/Churyumov-Gerasimenko near perihelion2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, p. S142-S148Article in journal (Refereed)
    Abstract [en]

    In 2015 August, comet 67P/Churyumov-Gerasimenko, the target comet of the ESA Rosetta mission, reached its perihelion at similar to 1.24 au. Here, we estimate for a three-day period near perihelion, effective ion speeds at distances similar to 200-250 km from the nucleus. We utilize two different methods combining measurements from the Rosetta Plasma Consortium (RPC)/Mutual Impedance Probe with measurements either from the RPC/Langmuir Probe or from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)/Comet Pressure Sensor (COPS) (the latter method can only be applied to estimate the effective ion drift speed). The obtained ion speeds, typically in the range 2-8 km s(-1), are markedly higher than the expected neutral outflow velocity of similar to 1 km s(-1). This indicates that the ions were de-coupled from the neutrals before reaching the spacecraft location and that they had undergone acceleration along electric fields, not necessarily limited to acceleration along ambipolar electric fields in the radial direction. For the limited time period studied, we see indications that at increasing distances from the nucleus, the fraction of the ions' kinetic energy associated with radial drift motion is decreasing.

12 1 - 50 of 61
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf