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  • 1.
    Andersson, L.
    et al.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Weber, T. D.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Malaspina, D.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Crary, F.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Ergun, R. E.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Fowler, C. M.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Morooka, M. W.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    McEnulty, T.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Eriksson, Anders. I.
    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.
    Horanyi, M.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Collette, A.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Yelle, R.
    Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA..
    Jakosky, B. M.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Dust observations at orbital altitudes surrounding Mars2015In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 350, no 6261, aad0398Article in journal (Refereed)
    Abstract [en]

    Dust is common close to the martian surface, but no known process can lift appreciable concentrations of particles to altitudes above similar to 150 kilometers. We present observations of dust at altitudes ranging from 150 to above 1000 kilometers by the Langmuir Probe and Wave instrument on the Mars Atmosphere and Volatile Evolution spacecraft. Based on its distribution, we interpret this dust to be interplanetary in origin. A comparison with laboratory measurements indicates that the dust grain size ranges from 1 to 12 micrometers, assuming a typical grain velocity of similar to 18 kilometers per second. These direct observations of dust entering the martian atmosphere improve our understanding of the sources, sinks, and transport of interplanetary dust throughout the inner solar system and the associated impacts on Mars's atmosphere.

  • 2.
    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, 3042-3058 p.Article 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.

  • 3.
    Andrews, David J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andersson, L.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Ergun, R. E.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fowler, C. M.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    McEnulty, T.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Morooka, M. W.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Weber, T.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Jakosky, B. M.
    Lab Atmospher & Space Phys, Boulder, CO USA..
    Ionospheric plasma density variations observed at Mars by MAVEN/LPW2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 21, 8862-8869 p.Article in journal (Refereed)
    Abstract [en]

    We report on initial observations made by the Langmuir Probe and Waves relaxation sounding experiment on board the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. These measurements yield the ionospheric thermal plasma density, and we use these data here for an initial survey of its variability. Studying orbit-to-orbit variations, we show that the relative variability of the ionospheric plasma density is lowest at low altitudes near the photochemical peak, steadily increases toward higher altitudes and sharply increases as the spacecraft crosses the terminator and moves into the nightside. Finally, despite the small volume of data currently available, we show that a clear signature of the influence of crustal magnetic fields on the thermal plasma density fluctuations is visible. Such results are consistent with previously reported remote measurements made at higher altitudes, but crucially, here we sample a new span of altitudes between similar to 130 and similar to 300 km using in situ techniques.

  • 4.
    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, 3944-3960 p.Article 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.

  • 5.
    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, 3139-3154 p.Article 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.

  • 6.
    Andrews, David J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cowley, S. W. H.
    Dougherty, M. K.
    Lamy, L.
    Provan, G.
    Southwood, D. J.
    Planetary period oscillations in Saturn's magnetosphere: Evolution of magnetic oscillation properties from southern summer to post-equinox2012In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117, A04224- p.Article in journal (Refereed)
    Abstract [en]

    We investigate the evolution of the properties of planetary period magnetic field oscillations observed by the Cassini spacecraft in Saturn's magnetosphere over the interval from late 2004 to early 2011, spanning equinox in mid-2009. Oscillations within the inner quasi-dipolar region (L <= 12) consist of two components of close but distinct periods, corresponding essentially to the periods of the northern and southern Saturn kilometric radiation (SKR) modulations. These give rise to modulations of the combined amplitude and phase at the beat period of the two oscillations, from which the individual oscillation amplitudes and phases (and hence periods) can be determined. Phases are also determined from northern and southern polar oscillation data when available. Results indicate that the southern-period amplitude declines modestly over this interval, while the northern-period amplitude approximately doubles to become comparable with the southern-period oscillations during the equinox interval, producing clear effects in pass-to-pass oscillation properties. It is also shown that the periods of the two oscillations strongly converge over the equinox interval, such that the beat period increases significantly from similar to 20 to more than 100 days, but that they do not coalesce or cross during the interval investigated, contrary to recent reports of the behavior of the SKR periods. Examination of polar oscillation data for similar beat phase effects yields a null result within a similar to 10% upper limit on the relative amplitude of northern-period oscillations in the south and vice versa. This result strongly suggests a polar origin for the two oscillation periods.

  • 7.
    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, 6228-6242 p.Article 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.

  • 8.
    Badman, S. V.
    et al.
    JAXA Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2525210, Japan..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cowley, S. W. H.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Lamy, L.
    Observ Paris, Meudon, France..
    Provan, G.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Tao, C.
    JAXA Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2525210, Japan..
    Kasahara, S.
    JAXA Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2525210, Japan..
    Kimura, T.
    JAXA Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2525210, Japan..
    Fujimoto, M.
    JAXA Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2525210, Japan..
    Melin, H.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Stallard, T.
    Univ Leicester, Dept Phys & Astron, Leicester, Leics, England..
    Brown, R. H.
    Univ Arizona, Lunar & Planetary Lab, Tucson, AZ USA..
    Baines, K. H.
    Univ Wisconsin Madison, SSEC, Madison, NJ USA..
    Rotational modulation and local time dependence of Saturn's infrared H-3(+) auroral intensity2012In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 117, A09228Article in journal (Refereed)
    Abstract [en]

    Planetary auroral emissions reveal the configuration of magnetospheric field-aligned current systems. In this study, Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of Saturn's pre-equinox infrared H-3(+) aurorae were analysed to show (a) rotational modulation of the auroral intensity in both hemispheres and (b) a significant local time dependence of the emitted intensity. The emission intensity is modulated by the 'planetary period' rotation of auroral current systems in each hemisphere. The northern auroral intensity also displays a lesser anti-phase dependence on the southern rotating current system, indicating that part of the southern current system closes in the northern hemisphere. The southern hemisphere aurorae were most intense in the post-dawn sector, in agreement with some past measurements of auroral field-aligned currents, UV aurora and SKR emitted power. A corresponding investigation of the northern hemisphere auroral intensity reveals a broader dawn-noon enhancement, possibly due to the interaction of the southern rotating current system with that of the north. The auroral intensity was reduced around dusk and post-midnight in both hemispheres. These observations can be explained by the interaction of a rotating field-aligned current system in each hemisphere with one fixed in local time, which is related to the solar wind interaction with magnetospheric field lines.

  • 9.
    Blanc, M.
    et al.
    Univ Toulouse 3, CNRS, IRAP, F-31062 Toulouse, France..
    Andrews, David. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Coates, A. J.
    Univ Coll London, Mullard Space Sci Lab, Dorking RH5 6NT, Surrey, England..
    Hamilton, D. C.
    Univ Maryland, Dept Phys, College Pk, MD 20742 USA..
    Jackman, C. M.
    Univ Southampton, Sch Phys & Astron, Southampton SO17 1BJ, Hants, England..
    Jia, X.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, Ann Arbor, MI 48109 USA..
    Kotova, A.
    Univ Toulouse 3, CNRS, IRAP, F-31062 Toulouse, France.;Max Planck Inst Solar Syst Res, Gottingen, Germany..
    Morooka, M.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Smith, H. T.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Westlake, J. H.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Saturn Plasma Sources and Associated Transport Processes2015In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 192, no 1-4, 237-283 p.Article, review/survey (Refereed)
    Abstract [en]

    This article reviews the different sources of plasma for Saturn's magnetosphere, as they are known essentially from the scientific results of the Cassini-Huygens mission to Saturn and Titan. At low and medium energies, the main plasma source is the cloud produced by the "geyser" activity of the small satellite Enceladus. Impact ionization of this cloud occurs to produce on the order of 100 kg/s of fresh plasma, a source which dominates all the other ones: Titan (which produces much less plasma than anticipated before the Cassini mission), the rings, the solar wind (a poorly known source due to the lack of quantitative knowledge of the degree of coupling between the solar wind and Saturn's magnetosphere), and the ionosphere. At higher energies, energetic particles are produced by energy diffusion and acceleration of lower energy plasma produced by the interchange instabilities induced by the rapid rotation of Saturn, and possibly, for the highest energy range, by contributions from the CRAND process acting inside Saturn's magnetosphere. Discussion of the transport and acceleration processes acting on these plasma sources shows the importance of rotation-induced radial transport and energization of the plasma, and also shows how much the unexpected planetary modulation of essentially all plasma parameters of Saturn's magnetosphere remains an unexplained mystery.

  • 10. Bunce, E. J.
    et al.
    Grodent, D. C.
    Jinks, S. L.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Badman, S. V.
    Coates, A. J.
    Cowley, S. W. H.
    Dougherty, M. K.
    Kurth, W. S.
    Mitchell, D. G.
    Provan, G.
    Cassini nightside observations of the oscillatory motion of Saturn's northern auroral oval2014In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, Vol. 119, no 5, 3528-3543 p.Article in journal (Refereed)
    Abstract [en]

    In recent years we have benefitted greatly from the first in-orbit multi-wavelength images of Saturn's polar atmosphere from the Cassini spacecraft. Specifically, images obtained from the Cassini UltraViolet Imaging Spectrograph (UVIS) provide an excellent view of the planet's auroral emissions, which in turn give an account of the large-scale magnetosphere-ionosphere coupling and dynamics within the system. However, obtaining near-simultaneous views of the auroral regions with in situ measurements of magnetic field and plasma populations at high latitudes is more difficult to routinely achieve. Here we present an unusual case, during Revolution 99 in January 2009, where UVIS observes the entire northern UV auroral oval during a 2h interval while Cassini traverses the magnetic flux tubes connecting to the auroral regions near 21 LT, sampling the related magnetic field, particle, and radio and plasma wave signatures. The motion of the auroral oval evident from the UVIS images requires a careful interpretation of the associated latitudinally oscillating magnetic field and auroral field-aligned current signatures, whereas previous interpretations have assumed a static current system. Concurrent observations of the auroral hiss (typically generated in regions of downward directed field-aligned current) support this revised interpretation of an oscillating current system. The nature of the motion of the auroral oval evident in the UVIS image sequence, and the simultaneous measured motion of the field-aligned currents (and related plasma boundary) in this interval, is shown to be related to the northern hemisphere magnetosphere oscillation phase. This is in agreement with previous observations of the auroral oval oscillatory motion.

  • 11.
    Cowley, S. W. H.
    et al.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    Provan, G.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Comment on "Magnetic phase structure of Saturn's 10.7h oscillations" by Yates et al.2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 7, 5686-5690 p.Article in journal (Other academic)
  • 12.
    Cowley, S. W. H.
    et al.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    Zarka, P.
    Univ Paris Diderot, Sorbonne Paris Cite, Univ Paris 06, Univ Paris 04,CNRS,PSL Res Univ,LESIA,Observ Pari, Meudon, France..
    Provan, G.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    Lamy, L.
    Univ Paris Diderot, Sorbonne Paris Cite, Univ Paris 06, Univ Paris 04,CNRS,PSL Res Univ,LESIA,Observ Pari, Meudon, France..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Comment on "A new approach to Saturn's periodicities" by J. F. Carbary2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 3, 2418-2422 p.Article in journal (Other academic)
  • 13.
    Dieval, C.
    et al.
    Univ Lancaster, Dept Phys, Lancaster, England.;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.
    Morgan, D. D.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Brain, D. A.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    MARSIS remote sounding of localized density structures in the dayside Martian ionosphere: A study of controlling parameters2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 9, 8125-8145 p.Article in journal (Refereed)
    Abstract [en]

    Enhanced topside electron densities in the dayside Martian ionosphere have been repetitively observed in areas of near-radial crustal magnetic fields, for periods of tens of days, indicating their long-term spatial and temporal stability despite changing solar wind conditions. We perform a statistical study of these density structures using the ionospheric mode of the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) onboard Mars Express. We estimate the apparent extents of these structures relative to the altitude of the surrounding ionosphere. The apex of the density structures often lies higher than the surrounding ionosphere (median vertical extent of 18km), which indicates upwellings. These structures are much wider than they are high, with latitudinal scales of several degrees. The radar reflector regions are observed above both moderate and strong magnetic anomalies, and their precise locations and latitudinal extents match quite well with the locations and latitudinal extents of magnetic structures of given magnetic polarity (oblique to vertical fields), which happen to be regions where the field lines are open part of the time. The majority of the density structures occur in regions where ionospheric plasma is dominant, indicating closed field regions shielded from shocked solar wind plasma.

  • 14.
    Dubinin, E.
    et al.
    Max Planck Inst Solar Syst Res, D-37077 Gottingen, Germany..
    Fraenz, M.
    Max Planck Inst Solar Syst Res, D-37077 Gottingen, Germany..
    Andrews, David
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morgan, D.
    Univ Iowa, Iowa City, IA USA..
    Martian ionosphere observed by Mars Express. 1. Influence of the crustal magnetic fields2016In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 124, 62-75 p.Article in journal (Refereed)
    Abstract [en]

    We present multi-instrument observations of the effects of the crustal magnetic field on the Martian ionosphere at different altitudes and solar zenith angles by Mars Express. Total electron content (TEC) at solar zenith angles 55 degrees >= SZA >= 105 degrees over the ionosphere with crustal sources increases with the strength of the magnetic field. A similar trend is observed in a dependence of the local electron density in the upper ionosphere on the crustal magnetic field. On the nightside, at SZA >= 110 degrees, the opposite trend of TEC increase with decrease in the magnetic field value is observed. A dependence on the magnetic field inclination also varies between the day and night sides. TEC decreases for vertical field inclination at 90 degrees >= SZA >= 70 degrees and increases at SZA >= 110 degrees. This effect becomes stronger for larger magnetic field values. A different dependence of the local electron densities in the upper ionosphere at small and high SZA is observed too. An ionospheric exhaust for vertical field inclination in the regions with strong crustal sources is probably caused by escape to space along open field lines which arise due to reconnection that is confirmed by the case studies. The existence of such localized ionospheric depressions is also observed by the in-situ plasma observations. In contrast, on the nightside downward plasma transport and electron precipitation along the field lines produce patches of enhanced ionization.

  • 15.
    Dubinin, E.
    et al.
    Max Planck Inst Solar Syst Res, D-37077 Gottingen, Germany..
    Fraenz, M.
    Max Planck Inst Solar Syst Res, D-37077 Gottingen, Germany..
    Paetzold, M.
    Rheinische Inst Umweltforsch, Abt Planetforsch, Cologne, Germany..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaisberg, O.
    Inst Space Res, Moscow, Russia..
    Zelenyi, L.
    Inst Space Res, Moscow, Russia..
    Barabash, S.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Martian ionosphere observed by Mars Express. 2. Influence of solar irradiance on upper ionosphere and escape fluxes2017In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 145, 1-8 p.Article in journal (Refereed)
    Abstract [en]

    We present multi-instrument observations of the effects of solar irradiance on the upper Martian ionosphere and escape fluxes based on Mars Express measurements obtained over almost 12 years. It is shown that the variations in the upper ionosphere caused by solar irradiance lead to significant changes in the trans-terminator fluxes of low-energy ions and total ion losses through the tail. The observed dependence of the electron number density in the upper ionosphere at altitudes above 300 km on solar irradiance implies that the ionosphere at such altitudes was denser by a factor of ten during the periods of solar maxima in solar cycles 22-23. Correspondingly, the trans terminator fluxes of cold ions and escape fluxes through the tail were also significantly higher. We estimate an increase of total ion losses through the tail during these solar maxima by a factor of 5-6.

  • 16.
    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, S45-S56 p.Article 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.

  • 17.
    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, 8884-8898 p.Article 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.

  • 18.
    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, 5255-5264 p.Article 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.

  • 19.
    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, 2879-2883 p.Article 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.

  • 20.
    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, 949-965 p.Article 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.

  • 21.
    Engelhardt, Ilka. A. D.
    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.
    Andrews, David J.
    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.
    Ye, S.
    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..
    Morooka, M. W.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Farrell, W. M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Dougherty, M. K.
    Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England..
    Plasma regions, charged dust and field-aligned currents near Enceladus2015In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 117, 453-469 p.Article in journal (Refereed)
    Abstract [en]

    We use data from several instruments on board Cassini to determine the characteristics of the plasma and dust regions around Saturn's moon Enceladus. For this we utilize the Langmuir probe and the electric antenna connected to the wideband receiver of the radio and plasma wave science (RPWS) instrument package as well as the magnetometer (MAG). We show that there are several distinct plasma and dust regions around Enceladus. Specifically they are the plume filled with neutral gas, plasma, and charged dust, with a distinct edge boundary region. Here we present observations of a new distinct plasma region, being a dust trail on the downstream side. This is seen both as a difference in ion and electron densities, indicating the presence of charged dust, and directly from the signals created on RPWS antennas by the dust impacts on the spacecraft. Furthermore, we show a very good scaling of these two independent dust density measurement methods over four orders of magnitude in dust density, thereby for the first time cross-validating them. To establish equilibrium with the surrounding plasma the dust becomes negatively charged by attracting free electrons. The dust distribution follows a simple power law and the smallest dust particles in the dust trail region are found to be 10 nm in size as well as in the edge region around the plume. Inside the plume the presence of even smaller particles of about 1 nm is inferred. From the magnetic field measurements we infer strong field-aligned currents at the geometrical edge of Enceladus.

  • 22.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Andersson, L. A.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Fowler, C. M.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Woodson, A. K.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Weber, T. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Andrews, David J.
    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.
    McEnulty, T.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Morooka, M. W.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Stewart, A. I. F.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Mahaffy, P. R.
    NASA, Goddard Space Flight Ctr, Planetary Environm Lab, Code 699, Greenbelt, MD USA..
    Jakosky, B. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Enhanced O-2(+) loss at Mars due to an ambipolar electric field from electron heating2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 5, 4668-4678 p.Article in journal (Refereed)
    Abstract [en]

    Recent results from the MAVEN Langmuir Probe and Waves instrument suggest higher than predicted electron temperatures (T-e) in Mars' dayside ionosphere above similar to 180km in altitude. Correspondingly, measurements from Neutral Gas and Ion Mass Spectrometer indicate significant abundances of O-2(+) up to similar to 500km in altitude, suggesting that O-2(+) may be a principal ion loss mechanism of oxygen. In this article, we investigate the effects of the higher T-e (which results from electron heating) and ion heating on ion outflow and loss. Numerical solutions show that plasma processes including ion heating and higher T-e may greatly increase O-2(+) loss at Mars. In particular, enhanced T-e in Mars' ionosphere just above the exobase creates a substantial ambipolar electric field with a potential (e) of several k(B)T(e), which draws ions out of the region allowing for enhanced escape. With active solar wind, electron, and ion heating, direct O-2(+) loss could match or exceed loss via dissociative recombination of O-2(+). These results suggest that direct loss of O-2(+) may have played a significant role in the loss of oxygen at Mars over time.

  • 23.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Morooka, M. W.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Andersson, L. A.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Fowler, C. M.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Andrews, David J.
    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.
    McEnulty, T.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Jakosky, B. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Dayside electron temperature and density profiles at Mars: First results from the MAVEN Langmuir probe and waves instrument2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 21, 8846-8853 p.Article in journal (Refereed)
    Abstract [en]

    We present Mars' electron temperature (T-e) and density (n(e)) altitude profiles derived from the MAVEN (Mars Atmosphere and Volatile EvolutioN) mission deep dip orbits in April 2015, as measured by the Langmuir probe instrument. These orbits had periapsides below 130 km in altitude at low solar zenith angles. The periapsides were above the peak in n(e) during this period. Using a Chapman function fit, we find that scale height and projected altitude of the n(e) peak are consistent with models and previous measurements. The peak electron density is slightly higher than earlier works. For the first time, we present in situ measurements of T-e altitude profiles in Mars' dayside in the altitude range from similar to 130 km to 500 km and provide a functional fit. Importantly, T-e rises rapidly with altitude from similar to 180 km to similar to 300 km. These results and functional fit are important for modeling Mars' ionosphere and understanding atmospheric escape.

  • 24.
    Fowler, C. M.
    et al.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Andersson, L.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Morooka, M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Delory, G.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lillis, Robert J.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    McEnulty, T.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Weber, T. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Chamandy, T. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mitchell, D. L.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Mazelle, C.
    Inst Rech Astrophys & Planetol, CNRS, Toulouse, France.;Univ Toulouse 3, Inst Rech Astrophys & Planetol, F-31062 Toulouse, France..
    Jakosky, B. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    The first in situ electron temperature and density measurements of the Martian nightside ionosphere2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 21, 8854-8861 p.Article in journal (Refereed)
    Abstract [en]

    The first in situ nightside electron density and temperature profiles at Mars are presented as functions of altitude and local time (LT) from the Langmuir Probe and Waves (LPW) instrument on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission spacecraft. LPW is able to measure densities as low as similar to 100 cm(-3), a factor of up to 10 or greater improvement over previous measurements. Above 200 km, near-vertical density profiles of a few hundred cubic centimeters were observed for almost all nightside LT, with the lowest densities and highest temperatures observed postmidnight. Density peaks of a few thousand cubic centimeters were observed below 200 km at all nightside LT. The lowest temperatures were observed below 180 km and approach the neutral atmospheric temperature. One-dimensional modeling demonstrates that precipitating electrons were able to sustain the observed nightside ionospheric densities below 200 km.

  • 25.
    Fowler, C. M.
    et al.
    University of Colorado Boulder, Laboratory for Atmospheric and Space Physics.
    Andersson, L.
    University of Colorado Boulder, Laboratory for Atmospheric and Space Physics.
    Halekas, J.
    University Of Iowa, Department of Physics And Astronomy.
    Espley, J. R.
    NASA, Goddard Space Flight Center.
    Mazelle, C.
    University of Toulouse, CNRS, UPS, IRAP,CNES.
    Coughlin, E. R.
    University of California Berkeley, Department Astronomy; University of California Berkeley, Theoretical Astrophysics Center; Einstein Fellow.
    Ergun, R. E.
    University of Colorado Boulder, Laboratory for Atmospheric and Space Physics.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Connerney, J. E. P.
    NASA, Goddard Space Flight Center.
    Jakosky, B.
    University of Colorado Boulder, Laboratory for Atmospheric and Space Physics.
    Electric and magnetic variations in the near-Mars environment2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 8, 8536-8559 p.Article in journal (Refereed)
    Abstract [en]

    For the first time at Mars the statistical distribution of (1-D) electric field wave power in the magnetosphere is presented, along with the distribution of magnetic field wave power, as observed by the Mars Atmosphere and Volatile EvolutioN spacecraft from the first 14.5months of the mission. Wave power in several different frequency bands was investigated, and the strongest wave powers were observed at the lowest frequencies. The presented statistical studies suggest that the full thermalization of ions within the magnetosheath does not appear to occur, as has been predicted by previous studies. Manual inspection of 140 periapsis passes on the dayside shows that Poynting fluxes (at 2-16 Hz) between similar to 10(-11) and 10(-8) Wm(-2) reach the upper ionosphere for all 140 cases. Wave power is not observed in the ionosphere for integrated electron densities greater than 10(10.8)cm(-2), corresponding to typical depths of 100-200 km. The observations presented support previous suggestions that energy from the Mars-solar wind interaction can propagate into the upper ionosphere and may provide an ionospheric heating source. Upstream of the shock, the orientation of the solar wind interplanetary magnetic field was shown to significantly affect the statistical distribution of wave power, based on whether the spacecraft was likely magnetically connected to the shock or not-something that is predicted but has not been quantitatively shown at Mars before. In flight performance and caveats of the Langmuir Probe and Waves electric field power spectra are also discussed.

  • 26.
    Fränz, M.
    et al.
    Max Planck Inst Sonnensyst Forsch, D-37077 Gottingen, Germany..
    Dubinin, E.
    Max Planck Inst Sonnensyst Forsch, D-37077 Gottingen, Germany..
    Andrews, David
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Barabash, S.
    Swedish Inst Space Phys, S-89128 Kiruna, Sweden..
    Nilsson, H.
    Swedish Inst Space Phys, S-89128 Kiruna, Sweden..
    Fedorov, A.
    Ctr Etud Spatiale Rayonnements, F-31028 Toulouse, France..
    Cold ion escape from the Martian ionosphere2015In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 119, 92-102 p.Article in journal (Refereed)
    Abstract [en]

    We here report on new measurements of the escape flux of oxygen ions from Mars by combining the observations of the ASPERA-3 and MARSIS experiments on board the European Mars Express spacecraft. We show that in previous estimates of the total heavy ion escape flow the contribution of the cold ionospheric outflow with energies below 10 eV has been underestimated. Both case studies and the derived flow pattern indicate that the cold plasma observed by MARSIS and the superthermal plasma observed by ASPERA-3 move with the same bulk speed in most regions of the Martian tail. We determine maps of the tailside heavy ion flux distribution derived from mean ion velocity distributions sampled over 7 years. If we assume that the superthermal bulk speed derived from these long time averages of the ion distribution function represent the total plasma bulk speed we derive the total tailside plasma flux. Assuming cylindrical symmetry we determine the mean total escape rate for the years 2007-2014 at 2.8 +/- 0.4 x 10(25) atoms/s which is in good agreement with model estimates. A possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside.

  • 27.
    Hall, B. E. S.
    et al.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England..
    Lester, M.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England..
    Nichols, J. D.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England..
    Sanchez-Cano, B.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England..
    Andrews, David J.
    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. Swedish Inst Space Phys, Uppsala, Sweden..
    Fraenz, M.
    Max Planck Inst Solar Syst Res, Gottingen, Germany..
    A survey of superthermal electron flux depressions, or "electron holes," within the illuminated Martian induced magnetosphere2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 5, 4835-4857 p.Article in journal (Refereed)
    Abstract [en]

    Since Mars lacks a global intrinsic magnetic field, the solar wind interacts directly with the Martian upper atmosphere and ionosphere. The presence of localized intense remnant crustal magnetic fields adds to this interaction, making the Martian plasma system a unique environment within the solar system. Rapid reductions in the electron flux, referred to as electron holes, occur within the Martian induced magnetosphere (IM). We present a statistical analysis of this phenomenon identified from proxy measurements of the electron flux derived from measurements by the Analyser of Space Plasmas and Energetic Neutral Atoms Electron Spectrometer experiment on board the Mars Express (MEX) spacecraft. The study is completed for the period of 9 February 2004 to 9 May 2014. Electron holes are observed within the IM in more than 56% of MEX orbits during this study period, occurring predominantly at altitudes less than 1300km, with the majority in the negative X Mars-Centric Solar Orbital direction. The spatial distribution above the surface of Mars is observed to bear close resemblance to that of the crustal magnetic fields as predicted by the Cain et al. [] magnetic field model, suggesting that they play an important role in the formation of these phenomena.

  • 28.
    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, 11474-11494 p.Article 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.

  • 29. Han, X.
    et al.
    Fraenz, M.
    Dubinin, E.
    Wei, Y.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wan, W.
    He, M.
    Rong, Z. J.
    Chai, L.
    Zhong, J.
    Li, K.
    Barabash, S.
    Discrepancy between ionopause and photoelectron boundary determined from Mars Express measurements2014In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, no 23, 8221-8227 p.Article in journal (Refereed)
    Abstract [en]

    The Martian ionosphere directly interacts with the solar wind due to lack of a significant intrinsic magnetic field, and an interface is formed in between. The interface is usually recognized by two kinds of indicators: the ionopause identified from ionospheric density profiles and the photoelectron boundary (PEB) determined from the electron energy spectrum at higher energies. However, the difference between them remains unclear. We have determined the locations of crossings of the ionopause and PEB from Mars Express observations during 2005-2013 and found that the average position of the PEB appears to be similar to 200km higher than that of the ionopause, which corresponds to 10(3)cm(-3) in the electron density profile. The discrepancy can be explained by cross-field transport of photoelectrons.

  • 30.
    Holmberg, Mika
    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.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cassidy, Tim
    Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA.
    Andrews, David
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Transport and chemical loss rates in Saturn's inner plasma disk2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 3, 2321-2334 p.Article in journal (Refereed)
    Abstract [en]

    The Kronian moon Enceladus is constantly feeding its surrounding with new gas and dust, from cryovolcanoes located in its south polar region. Through photoionization and impact ionization of the neutrals a plasma disk is created, which mainly contains hydrogen ions H+ and water group ions W+. This paper investigates the importance of ion loss by outward radial transport and ion loss by dissociative recombination, which is the dominant chemical loss process in the inner plasma disk. We use plasma densities derived from several years of measurements by the Cassini Radio and Plasma Wave Science (RPWS) electric field spectrums and Langmuir probe (LP), to derive the total flux tube content NL2. Our calculation show that NL2 agrees well with earlier estimates within L shell 8. We also show that loss by transport dominates chemical loss in between L shell 2.5 and 10. The loss rate by transport is ∼5 times larger at 5 Saturn radii (1 RS = 60,268 km) and the difference is increasing as L7.7 for larger radial distances, for the total ion population. Chemical loss may still be important for the structure of the plasma disk in the region closest to Enceladus (∼±0.5 RS) at 3.95 RS, since the transport and chemical loss rates only differ by a factor of ∼2 in this region. We also derive the total plasma content of the plasma disk from L shell 4 to 10 to be 1.9×10^33 ions, and the total ion source rate for the same region to be 5.8×10^27 s^−1. The equatorial ion production rate P, ranges from 2.6×10^−5 cm^−3s^−1 (at L = 10) to 1.1×10^−4 cm^−3s^−1 (at L = 4.8). The net mass loading rate is derived to be 123 kg/s for L shell 4 to 10. 

  • 31.
    Jakosky, B. M.
    et al.
    Univ Colorado, Boulder, CO 80309 USA..
    Grebowsky, J. M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Luhmann, J. G.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Connerney, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Eparvier, F.
    Univ Colorado, Boulder, CO 80309 USA..
    Ergun, R.
    Univ Colorado, Boulder, CO 80309 USA..
    Halekas, J.
    Univ Iowa, Iowa City, IA USA..
    Larson, D.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Mahaffy, P.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    McFadden, J.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Mitchell, D. F.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Schneider, N.
    Univ Colorado, Boulder, CO 80309 USA..
    Zurek, R.
    CALTECH, Jet Prop Lab, Pasadena, CA USA..
    Bougher, S.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Brain, D.
    Univ Colorado, Boulder, CO 80309 USA..
    Ma, Y. J.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Mazelle, C.
    CNRS, IRAP, Toulouse, France.;Univ Paul Sabatier, Toulouse, France..
    Andersson, L.
    Univ Colorado, Boulder, CO 80309 USA..
    Andrews, David
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Baird, D.
    NASA, Lyndon B Johnson Space Ctr, Houston, TX 77058 USA..
    Baker, D.
    Univ Colorado, Boulder, CO 80309 USA..
    Bell, J. M.
    Natl Inst Aerosp, Hampton, VA USA..
    Benna, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Chaffin, M.
    Univ Colorado, Boulder, CO 80309 USA..
    Chamberlin, P.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Chaufray, Y. -Y
    Clarke, J.
    Boston Univ, Boston, MA 02215 USA..
    Collinson, G.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Combi, M.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Crary, F.
    Univ Colorado, Boulder, CO 80309 USA..
    Cravens, T.
    Univ Kansas, Lawrence, KS 66045 USA..
    Crismani, M.
    Univ Colorado, Boulder, CO 80309 USA..
    Curry, S.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Curtis, D.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Deighan, J.
    Univ Colorado, Boulder, CO 80309 USA..
    Delory, G.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Dewey, R.
    Univ Colorado, Boulder, CO 80309 USA..
    DiBraccio, G.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Dong, C.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Dong, Y.
    Univ Colorado, Boulder, CO 80309 USA..
    Dunn, P.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Elrod, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    England, S.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Espley, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Evans, S.
    Computat Phys Inc, Boulder, CO USA..
    Fang, X.
    Univ Colorado, Boulder, CO 80309 USA..
    Fillingim, M.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Fortier, K.
    Univ Colorado, Boulder, CO 80309 USA..
    Fowler, C. M.
    Univ Colorado, Boulder, CO 80309 USA..
    Fox, J.
    Wright State Univ, Dayton, OH 45435 USA..
    Groeller, H.
    Univ Arizona, Tucson, AZ USA..
    Guzewich, S.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Hara, T.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Harada, Y.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Holsclaw, G.
    Univ Colorado, Boulder, CO 80309 USA..
    Jain, S. K.
    Univ Colorado, Boulder, CO 80309 USA..
    Jolitz, R.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Leblanc, F.
    CNRS, Lab Atmospheres Milieux & Observat Spatiales, Paris, France..
    Lee, C. O.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Lee, Y.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Lefevre, F.
    CNRS, Lab Atmospheres Milieux & Observat Spatiales, Paris, France..
    Lillis, R.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Livi, R.
    Univ Calif Berkeley, Berkeley, CA 94720 USA..
    Lo, D.
    Univ Arizona, Tucson, AZ USA..
    Mayyasi, M.
    Boston Univ, Boston, MA 02215 USA..
    McClintock, W.
    Univ Colorado, Boulder, CO 80309 USA..
    McEnulty, T.
    Univ Colorado, Boulder, CO 80309 USA..
    Modolo, R.
    CNRS, Lab Atmospheres Milieux & Observat Spatiales, Paris, France..
    Montmessin, F.
    CNRS, Lab Atmospheres Milieux & Observat Spatiales, Paris, France..
    Morooka, M.
    Univ Colorado, Boulder, CO 80309 USA..
    Nagy, A.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Olsen, K.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Peterson, W.
    Univ Colorado, Boulder, CO 80309 USA..
    Rahmati, A.
    Univ Kansas, Lawrence, KS 66045 USA..
    Ruhunusiri, S.
    Univ Iowa, Iowa City, IA USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Sakai, S.
    Univ Kansas, Lawrence, KS 66045 USA..
    Sauvaud, J. -A
    Seki, K.
    Nagoya Univ, Nagoya, Aichi 4648601, Japan..
    Steckiewicz, M.
    CNRS, IRAP, Toulouse, France.;Univ Paul Sabatier, Toulouse, France..
    Stevens, M.
    Naval Res Lab, Washington, DC 20375 USA..
    Stewart, A. I. F.
    Univ Colorado, Boulder, CO 80309 USA..
    Stiepen, A.
    Univ Colorado, Boulder, CO 80309 USA..
    Stone, S.
    Univ Arizona, Tucson, AZ USA..
    Tenishev, V.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Thiemann, E.
    Univ Colorado, Boulder, CO 80309 USA..
    Tolson, R.
    N Carolina State Univ, Raleigh, NC 27695 USA..
    Toublanc, D.
    CNRS, IRAP, Toulouse, France.;Univ Paul Sabatier, Toulouse, France..
    Vogt, M.
    Boston Univ, Boston, MA 02215 USA..
    Weber, T.
    Univ Colorado, Boulder, CO 80309 USA..
    Withers, P.
    Boston Univ, Boston, MA 02215 USA..
    Woods, T.
    Univ Colorado, Boulder, CO 80309 USA..
    Yelle, R.
    Univ Arizona, Tucson, AZ USA..
    MAVEN observations of the response of Mars to an interplanetary coronal mass ejection2015In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 350, no 6261, aad0210Article in journal (Refereed)
    Abstract [en]

    Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-term evolution of the Mars atmosphere.

  • 32.
    Nemec, F.
    et al.
    Charles Univ Prague, Fac Math & Phys, Prague, Czech Republic..
    Morgan, D. D.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Gurnett, D. A.
    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.
    Empirical model of the Martian dayside ionosphere: Effects of crustal magnetic fields and solar ionizing flux at higher altitudes2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 2, 1760-1771 p.Article in journal (Refereed)
    Abstract [en]

    We use electron density profiles measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument on board the Mars Express spacecraft to investigate the effects of possible controlling parameters unconsidered in the empirical model of Nemec et al. (2011, hereafter N11). Specifically, we focus on the effects of crustal magnetic fields and F-10.7 proxy of the solar ionizing flux at higher altitudes. It is shown that while peak electron densities are nearly unaffected by crustal magnetic fields, electron densities at higher altitudes are significantly increased in areas of stronger magnetic fields. The magnetic field inclination appears to have only a marginal effect. Moreover, while the N11 empirical model accounted for the variable solar ionizing flux at low altitudes, the high-altitude diffusive region was parameterized only by the solar zenith angle and the altitude. It is shown that this can lead to considerable inaccuracies. A simple correction of the N11 model, which takes into account both the crustal magnetic field magnitude and the effect of F-10.7 at higher altitudes, is suggested.

  • 33.
    Opgenoorth, Hermann J.
    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.
    Fraenz, M.
    Lester, M.
    Edberg, N. J. T.
    Morgan, D.
    Duru, F.
    Witasse, O.
    Williams, A. O.
    Mars ionospheric response to solar wind variability2013In: Journal of Geophysical Research: Space Physics, ISSN 2169-9380, Vol. 118, no 10, 6558-6587 p.Article in journal (Refereed)
    Abstract [en]

    At planets with induced magnetospheres, the coupling between the ionosphere, the weak draped magnetosphere, and the solar wind is very direct in comparison to Earth. The weak induced magnetosphere itself is created by the prevailing Solar wind conditions and therefore in its shape and strength dynamically depending on it. In early 2010, Mars was located behind Earth in the Solar wind; thus, we can use coordinated data from multiple near-Earth spacecraft (Stereo, Wind) to evaluate what kind of Solar wind disturbances have passed by Earth and might consecutively hit Mars, and when. We employ plasma data from the ESA Mars-Express mission, the ASPERA-3 particle instrument, and the MARSIS Active Ionospheric Sounder (AIS) to investigate, for a number of isolated events in March and April 2010, how the ionosphere and the induced magnetosphere at Mars develop and decay in response to Solar wind variability in the magnetic field, density, and velocity. In a dedicated campaign mode, we use frequent long-duration MARSIS AIS operations for several consecutive orbits, to monitor for the first time the long-term development of the Martian plasma environment during solar wind disturbances. We find that the magnetosphere and ionosphere of Mars can become considerably compressed by solar wind dynamic pressure variations, which usually are also associated with changes in the magnetic draping of the interplanetary magnetic field around the planet. These are typically associated with corotating interaction regions and coronal mass ejections, and can last for several days. During such episodes of compression, we see signatures of increased plasma transport over the terminator and enhanced ion outflow from the upper atmosphere.

  • 34. Provan, G.
    et al.
    Cowley, S. W. H.
    Sandhu, J.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dougherty, M. K.
    Planetary period magnetic field oscillations in Saturn's magnetosphere: Postequinox abrupt nonmonotonic transitions to northern system dominance2013In: Journal of Geophysical Research-Space Physics, ISSN 2169-9380, Vol. 118, no 6, 3243-3264 p.Article in journal (Refereed)
    Abstract [en]

    We examine the planetary period magnetic field oscillations observed in the core region of Saturn's magnetosphere (dipole L12), on 56 near-equatorial Cassini periapsis passes that took place between vernal equinox in August 2009 and November 2012. Previous studies have shown that these consist of the sum of two oscillations related to the northern and southern polar regions having differing amplitudes and periods that had reached near-equal amplitudes and near-converged periods 10.68 h in the interval to 1 year after equinox. The present analysis shows that an interval of strongly differing behavior then began 1.5 years after equinox, in which abrupt changes in properties took place at 6- to 8-month intervals, with three clear transitions occurring in February 2011, August 2011, and April 2012, respectively. These are characterized by large simultaneous changes in the amplitudes of the two systems, together with small changes in period about otherwise near-constant values of 10.63 h for the northern system and 10.69 h for the southern (thus, not reversed postequinox) and on occasion jumps in phase. The first transition produced a resumption of strong southern system dominance unexpected under northern spring conditions, while the second introduced comparably strong northern system dominance for the first time in these data. The third resulted in suppression of all core oscillations followed by re-emergence of both systems on a time scale of 85 days, with the northern system remaining dominant but not as strongly as before. This behavior poses interesting questions for presently proposed theoretical scenarios.

  • 35.
    Sanchez-Cano, B.
    et al.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England..
    Hall, B. E. S.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England..
    Lester, M.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England..
    Mays, M. L.
    NASA Goddard Space Flight Ctr, Heliophys Sci Div, Greenbelt, MD USA..
    Witasse, O.
    ESTEC Sci Support Off, European Space Agcy, Noordwijk, Netherlands..
    Ambrosi, R.
    Univ Leicester, Dept Phys & Astron, Space Res Ctr, Leicester, Leics, England..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cartacci, M.
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Cicchetti, A.
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Holmstrom, M.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Imber, S.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England..
    Kajdic, P.
    Univ Nacl Autonoma Mexico, Inst Geofis, Ciudad Univ, Mexico City, DF, Mexico..
    Milan, S. E.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England..
    Noschese, R.
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Odstrcil, D.
    George Mason Univ, Sch Phys Astron & Computat Sci, Fairfax, VA 22030 USA..
    Opgenoorth, Hermann J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Plaut, J.
    Jet Prop Lab, Pasadena, CA USA..
    Ramstad, R.
    Swedish Inst Space Phys, Kiruna, Sweden..
    Reyes-Ayala, K. I.
    Univ Nacl Autonoma Mexico, Inst Geofis, Ciudad Univ, Mexico City, DF, Mexico..
    Mars plasma system response to solar wind disturbances during solar minimum2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 6, 6611-6634 p.Article in journal (Refereed)
    Abstract [en]

    This paper is a phenomenological description of the ionospheric plasma and induced magnetospheric boundary (IMB) response to two different types of upstream solar wind events impacting Mars in March 2008, at the solar minimum. A total of 16 Mars Express orbits corresponding to five consecutive days is evaluated. Solar TErrestrial RElations Observatory-B (STEREO-B) at 1AU and Mars Express and Mars Odyssey at 1.644AU detected the arrival of a small transient interplanetary coronal mass ejection (ICME-like) on the 6 and 7 of March, respectively. This is the first time that this kind of small solar structure is reported at Mars's distance. In both cases, it was followed by a large increase in solar wind velocity that lasted for similar to 10days. This scenario is simulated with the Wang-Sheeley-Arge (WSA) - ENLIL + Cone solar solar wind model. At Mars, the ICME-like event caused a strong compression of the magnetosheath and ionosphere, and the recovery lasted for similar to 3 orbits (similar to 20h). After that, the fast stream affected the upper ionosphere and the IMB, which radial and tangential motions in regions close to the subsolar point are analyzed. Moreover, a compression in the Martian plasma system is also observed, although weaker than after the ICME-like impact, and several magnetosheath plasma blobs in the upper ionosphere are detected by Mars Express. We conclude that, during solar minimum and at aphelion, small solar wind structures can create larger perturbations than previously expected in the Martian system.

  • 36.
    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, 10075-10090 p.Article 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.

  • 37.
    Vogt, Marissa F.
    et al.
    Boston Univ, Ctr Space Phys, Boston, MA 02215 USA..
    Withers, Paul
    Boston Univ, Ctr Space Phys, Boston, MA 02215 USA.;Boston Univ, Dept Astron, 725 Commonwealth Ave, Boston, MA 02215 USA..
    Fallows, Kathryn
    Boston Univ, Ctr Space Phys, Boston, MA 02215 USA..
    Flynn, Casey L.
    Boston Univ, Dept Astron, 725 Commonwealth Ave, Boston, MA 02215 USA..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Duru, Firdevs
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Morgan, David D.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Electron densities in the ionosphere of Mars: A comparison of MARSIS and radio occultation measurements2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 10, 10241-10257 p.Article in journal (Refereed)
    Abstract [en]

    Radio occultation electron densities measurements from the Mariner 9 and Viking spacecraft, which orbited Mars in the 1970s, have recently become available in a digital format. These data are highly complementary to the radio occultation electron density profiles from Mars Global Surveyor, which were restricted in solar zenith angle and altitude. Wehave compiled data from the Mariner 9, Viking, and Mars Global Surveyor radio occultation experiments for comparison to electron density measurements made by Mars AdvancedRadar for SubsurfaceandIonosphere Sounding (MARSIS), the topside radar sounder on Mars Express, and MARSIS-based empirical density models. Wefind that the electron densities measured by radio occultation are in generally good agreement with the MARSIS data and model, especially near the altitude of the peak electron density but that the MARSIS data and model display a larger plasma scale height than the radio occultation profiles at altitudes between the peak density and 200 km. Consequently, the MARSIS-measured and model electron densities are consistently larger than radio occultation densities at altitudes similar to 200-300 km. Finally, we have analyzed transitions in the topside ionosphere, at the boundary between the photochemically controlled and transport-controlled regions, and identified the average transition altitude, or altitude at which a change in scale height occurs. The average transition altitude is similar to 200 km in the Mariner 9 and Viking radio occultation profiles and in profiles of the median MARSIS radar sounding electron densities.

  • 38.
    Witasse, O.
    et al.
    European Space Agcy, ESTEC.
    Sanchez-Cano, B.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp.
    Mays, M. L.
    NASA Goddard Space Flight Ctr, Heliophys Sci Div.
    Kajdic, P.
    Univ Nacl Autonoma Mexico, Inst Geofis.
    Opgenoorth, Hermann
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Elliott, H. A.
    Southwest Res Inst, San Antonio.
    Richardson, I. G.
    NASA Goddard Space Flight Ctr, Heliophys Sci Div.;Univ Maryland, Dept Astron.
    Zouganelis, I.
    European Space Agcy, ESAC, Villanueva De La Canada.
    Zender, J.
    European Space Agcy, ESTEC.
    Wimmer-Schweingruber, R. F.
    Univ Kiel, Inst Expt & Appl Phys.
    Turc, L.
    European Space Agcy, ESTEC.
    Taylor, M. G. G. T.
    European Space Agcy, ESTEC.
    Roussos, E.
    Max Planck Inst Solar Syst Res Justus von Liebig.
    Rouillard, A.
    IRAP, Toulouse.
    Richter, I.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterrestrial Phys.
    Richardson, J. D.
    MIT, Ctr Space Res, Cambridge.
    Ramstad, R.
    Swedish Inst Space Phys, IRF, Kiruna.
    Provan, G.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp.
    Posner, A.
    NASA Headquarters, Sci Miss Directorate.
    Plaut, J. J.
    Jet Prop Lab, Pasadena.
    Odstrcil, D.
    George Mason Univ, Dept Phys & Astron.;NASA Goddard Space Flight Ctr, Space Weather Lab.
    Nilsson, H.
    Swedish Inst Space Phys, IRF, Kiruna.
    Niemenen, P.
    European Space Agcy, ESTEC.
    Milan, S. E.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp.
    Mandt, K.
    Southwest Res Inst, San Antonio.; UTSA, Dept Phys & Astron, San Antonio.
    Lohf, H.
    Univ Kiel, Inst Expt & Appl Phys.
    Lester, M.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp.
    Lebreton, J. -P
    Univ Orleans, CNRS, LPC2E.
    Kuulkers, E.
    European Space Agcy, ESTEC.
    Krupp, N.
    Max Planck Inst Solar Syst Res Justus von Liebig.
    Koenders, C.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterrestrial Phys.
    James, M. K.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp.
    Intzekara, D.
    European Space Agcy, ESTEC.; European Space Agcy, ESAC, Villanueva De La Canada.
    Holmstrom, M.
    Swedish Inst Space Phys, IRF, Kiruna.
    Hassler, D. M.
    Southwest Res Inst, Boulder.; Inst Astrophys Spatiale, Orsay.
    Hall, B. E. S.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp.
    Guo, J.
    Univ Kiel, Inst Expt & Appl Phys.
    Goldstein, R.
    Southwest Res Inst, San Antonio.
    Goetz, C.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterrestrial Phys.
    Glassmeier, K. H.
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterrestrial Phys.
    Genot, V.
    IRAP, Toulouse.
    Evans, H.
    European Space Agcy, ESTEC.
    Espley, J.
    Goddard Space Flight Ctr, Lab Planetary Magnetospheres, Greenbelt.
    Edberg, N. J. T.
    Swedish Inst Space Phys, IRF, Uppsala, Sweden..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cowley, S. W. H.
    Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp.
    Burch, J.
    Southwest Res Inst, San Antonio.
    Behar, E.
    Swedish Inst Space Phys, IRF, Kiruna.
    Barabash, S.
    Swedish Inst Space Phys, IRF, Kiruna.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Altobelli, N.
    European Space Agcy, ESAC, Villanueva De La Canada.
    Interplanetary coronal mass ejection observed at STEREO-A, Mars, comet 67P/Churyumov-Gerasimenko, Saturn, and New Horizons en route to Pluto: Comparison of its Forbush decreases at 1.4, 3.1, and 9.9 AU2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 8, 7865-7890 p.Article in journal (Refereed)
    Abstract [en]

    We discuss observations of the journey throughout the Solar System of a large interplanetary coronal mass ejection (ICME) that was ejected at the Sun on 14 October 2014. The ICME hit Mars on 17 October, as observed by the Mars Express, Mars Atmosphere and Volatile EvolutioN Mission (MAVEN), Mars Odyssey, and Mars Science Laboratory (MSL) missions, 44h before the encounter of the planet with the Siding-Spring comet, for which the space weather context is provided. It reached comet 67P/Churyumov-Gerasimenko, which was perfectly aligned with the Sun and Mars at 3.1 AU, as observed by Rosetta on 22 October. The ICME was also detected by STEREO-A on 16 October at 1 AU, and by Cassini in the solar wind around Saturn on the 12 November at 9.9AU. Fortuitously, the New Horizons spacecraft was also aligned with the direction of the ICME at 31.6 AU. We investigate whether this ICME has a nonambiguous signature at New Horizons. A potential detection of this ICME by Voyager 2 at 110-111 AU is also discussed. The multispacecraft observations allow the derivation of certain properties of the ICME, such as its large angular extension of at least 116 degrees, its speed as a function of distance, and its magnetic field structure at four locations from 1 to 10 AU. Observations of the speed data allow two different solar wind propagation models to be validated. Finally, we compare the Forbush decreases (transient decreases followed by gradual recoveries in the galactic cosmic ray intensity) due to the passage of this ICME at Mars, comet 67P, and Saturn.

1 - 38 of 38
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