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  • 1. Agapitov, Oleksiy
    et al.
    Artemyev, Anton
    Krasnoselskikh, Vladimir
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mourenas, Didier
    Breuillard, Hugo
    Balikhin, Michael
    Rolland, Guy
    Statistics of whistler mode waves in the outer radiation belt: Cluster STAFF-SA measurements2013In: Journal of Geophysical Research-Space Physics, ISSN 2169-9380, Vol. 118, no 6, 3407-3420 p.Article in journal (Refereed)
    Abstract [en]

    ELF/VLF waves play a crucial role in the dynamics of the radiation belts and are partly responsible for the main losses and the acceleration of energetic electrons. Modeling wave-particle interactions requires detailed information of wave amplitudes and wave normal distribution over L-shells and over magnetic latitudes for different geomagnetic activity conditions. We performed a statistical study of ELF/VLF emissions using wave measurements in the whistler frequency range for 10years (2001-2010) aboard Cluster spacecraft. We utilized data from the STAFF-SA experiment, which spans the frequency range from 8Hz to 4kHz. We present distributions of wave magnetic and electric field amplitudes and wave normal directions as functions of magnetic latitude, magnetic local time, L-shell, and geomagnetic activity. We show that wave normals are directed approximately along the background magnetic field (with the mean value of the angle between the wave normal and the background magnetic field, about 10 degrees-15 degrees) in the vicinity of the geomagnetic equator. The distribution changes with magnetic latitude: Plasmaspheric hiss normal angles increase with latitude to quasi-perpendicular direction at approximate to 35 degrees-40 degrees where hiss can be reflected; lower band chorus are observed as two wave populations: One population of wave normals tends toward the resonance cone and at latitudes of around 35 degrees-45 degrees wave normals become nearly perpendicular to the magnetic field; the other part remains quasi-parallel at latitudes up to 30 degrees. The observed angular distribution is significantly different from Gaussian, and the width of the distribution increases with latitude. Due to the rapid increase of , the wave mode becomes quasi-electrostatic, and the corresponding electric field increases with latitude and has a maximum near 30 degrees. The magnetic field amplitude of the chorus in the day sector has a minimum at the magnetic equator but increases rapidly with latitude with a local maximum near 12 degrees-15 degrees. The wave magnetic field maximum is observed in the night sector at L>7 during low geomagnetic activity (at L approximate to 5 for K-p>3). Our results confirm the strong dependence of wave amplitude on geomagnetic activity found in earlier studies.

  • 2. Agapitov, Oleksiy
    et al.
    Krasnoselskikh, Vladimir
    de Wit, Thierry Dudok
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Pickett, Jolene S.
    Santolik, Ondrej
    Rolland, Guy
    Multispacecraft observations of chorus emissions as a tool for the plasma density fluctuations' remote sensing2011In: Journal of Geophysical Research, ISSN 0148-0227, Vol. 116, A09222- p.Article in journal (Refereed)
    Abstract [en]

    Discrete ELF/VLF chorus emissions are the most intense electromagnetic plasma waves that are observed in the radiation belts and in the outer magnetosphere of the Earth. They are assumed to propagate approximately along the magnetic field lines and are generated in source regions in the vicinity of the magnetic equator and in minimum B pockets in the dayside outer zone of the magnetosphere. The presence of plasma density irregularities along the raypath causes a loss of phase coherence of the chorus wave packets. These irregularities are often present around the plasmapause and in the radiation belts; they occur at scales ranging from a few meters up to several hundred kilometers and can be highly anisotropic. Such irregularities result in fluctuations of the dielectric permittivity, whose statistical properties can be studied making use of intersatellite correlations of whistler waves' phases and amplitudes. We demonstrate how the whistler-mode wave properties can be used to infer statistical characteristics of the density fluctuations. The analogy between weakly coupled oscillators under the action of uncorrelated random forces and wave propagation in a randomly fluctuating medium is used to determine the wave phase dependence on the duration of signal recording time. We study chorus whistler-mode waves observed by the Cluster WBD instrument and apply intersatellite correlation analysis to determine the statistical characteristics of the waveform phases and amplitudes. We then infer the statistical characteristics of the plasma density fluctuations and evaluate the spatial distribution of the irregularities using the same chorus events observed by the four Cluster spacecraft.

  • 3. Agapitov, Oleksiy
    et al.
    Krasnoselskikh, Vladimir
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Rolland, Guy
    A statistical study of the propagation characteristics of whistler waves observed by Cluster2011In: Geophysical Research Letters, ISSN 0094-8276, Vol. 38, L20103- p.Article in journal (Refereed)
    Abstract [en]

    VLF waves play a crucial role in the dynamics of radiation belts, and are responsible for the loss and the acceleration of energetic electrons. Modeling wave-particle interactions requires the best possible knowledge for how wave energy and wave-normal directions are distributed in L-shells and for the magnetic latitudes of different magnetic activity conditions. In this work, we performed a statistical study for VLF emissions using a whistler frequency range for nine years (2001-2009) of Cluster measurements. We utilized data from the STAFF-SA experiment, which spans the frequency range from 8.8 Hz to 3.56 kHz. We show that the wave energy distribution has two maxima around L similar to 4.5 = 6 and L similar to 2, and that wave-normals are directed approximately along the magnetic field in the vicinity of the geomagnetic equator. The distribution changes with magnetic latitude, and so that at latitudes of similar to 30 degrees, wave-normals become nearly perpendicular to the magnetic field. The observed angular distribution is significantly different from Gaussian and the width of the distribution increases with latitude. Since the resonance condition for wave-particle interactions depends on the wave normal orientation, our results indicate that, due to the observed change in the wave-normal direction with latitude, the most efficient particle diffusion due to wave-particle interaction should occur in a limited region surrounding the geomagnetic equator.

  • 4. Aikio, A. T.
    et al.
    Pitkanen, T.
    Fontaine, D.
    Dandouras, I.
    Amm, O.
    Kozlovsky, A.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fazakerley, A.
    EISCAT and Cluster observations in the vicinity of the dynamical polar cap boundary2008In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, no 1, 87-105 p.Article in journal (Refereed)
    Abstract [en]

    The dynamics of the polar cap boundary and auroral oval in the nightside ionosphere are studied during late expansion and recovery of a substorm from the region between Tromso (66.6 degrees cgmLat) and Longyearbyen (75.2 degrees cgmLat) on 27 February 2004 by using the coordinated EISCAT incoherent scatter radar, MIRACLE magnetometer and Cluster satellite measurements. During the late substorm expansion/early recovery phase, the polar cap boundary (PCB) made zig-zag-type motion with amplitude of 2.5 degrees cgmLat and period of about 30 min near magnetic midnight. We suggest that the poleward motions of the PCB were produced by bursts of enhanced reconnection at the near-Earth neutral line (NENL). The subsequent equatorward motions of the PCB would then represent the recovery of the merging line towards the equilibrium state (Cowley and Lockwood, 1992). The observed bursts of enhanced westward electrojet just equatorward of the polar cap boundary during poleward expansions were produced plausibly by particles accelerated in the vicinity of the neutral line and thus lend evidence to the Cowley-Lockwood paradigm. During the substorm recovery phase, the footpoints of the Cluster satellites at a geocentric distance of 4.4 R-E mapped in the vicinity of EISCAT measurements. Cluster data indicate that outflow of H+ and O+ ions took place within the plasma sheet boundary layer (PSBL) as noted in some earlier studies as well. We show that in this case the PSBL corresponded to a region of enhanced electron temperature in the ionospheric F region. It is suggested that the ion outflow originates from the F region as a result of increased ambipolar diffusion. At higher altitudes, the ions could be further energized by waves, which at Cluster altitudes were observed as BBELF (broad band extra low frequency) fluctuations. The four-satellite configuration of Cluster revealed a sudden poleward expansion of the PSBL by 2 degrees during similar to 5 min. The beginning of the poleward motion of the PCB was associated with an intensification of the downward FAC at the boundary. We suggest that the downward FAC sheet at the PCB is the high-altitude counterpart of the Earthward flowing FAC produced in the vicinity of the magnetotail neutral line by the Hall effect (Sonnerup, 1979) during a short-lived reconnection pulse.

  • 5.
    Alexandersson, Ilona
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Comet Ion Tail Observations Far From the Nucleus2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    On may 1, 1996, Ulysses spacecraft crossed the ion tail of comet Hyakutake, revealing an ion tail length of more than 3 times the Sun-Earth distance. The signatures of an ion tail, especially the ion tail far from the nucleus, are not well explored and many question marks remain. This report summarizes previous observations of spacecraft - ion tail crossings and what signatures that can be expected, as well as signatures of other known solar wind structures. A data analysis is made of possible ion tail encounters from Rosetta spacecraft measurements, Ulysses spacecraft measurements and Earth-orbiting spacecraft measurements. A search from Venus Express data to detect ion tails of sungrazing comets is presented.

  • 6. Allen, R. C.
    et al.
    Zhang, J. -C
    Kistler, L. M.
    Spence, H. E.
    Lin, R. -L
    Dunlop, M. W.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Multiple bidirectional EMIC waves observed by Cluster at middle magnetic latitudes in the dayside magnetosphere2013In: Journal of Geophysical Research: Space Physics, ISSN 2169-9380, Vol. 118, no 10, 6266-6278 p.Article in journal (Refereed)
    Abstract [en]

    It is well accepted that the propagation of electromagnetic ion cyclotron (EMIC) waves are bidirectional near their source regions and unidirectional when away from these regions. The generally believed source region for EMIC waves is around the magnetic equatorial plane. Here we describe a series of EMIC waves in the Pc1 (0.2-5 Hz) frequency band above the local He+ cyclotron frequency observed in situ by all four Cluster spacecraft on 9 April 2005 at midmagnetic latitudes (MLAT = similar to 33 degrees-49 degrees) with L = 10.7-11.5 on the dayside (MLT = 10.3-10.4). A Poynting vector spectrum shows that the wave packets consist of multiple groups of packets propagating bidirectionally, rather than unidirectionally, away from the equator, while the local plasma conditions indicate that the spacecraft are entering into a region sufficient for local wave excitation. One possible interpretation is that, while part of the observed waves are inside their source region, the others are either close enough to the source region, or mixed with the wave packets from multiple source regions at different latitudes.

  • 7.
    Allen, R. C.
    et al.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Zhang, J. -C
    Kistler, L. M.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Spence, H. E.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Lin, R. -L
    Klecker, B.
    Max Planck Inst Extraterr Phys, D-85748 Garching, Germany..
    Dunlop, M. W.
    Rutherford Appleton Lab, Space Sci Div, SSTD, Didcot OX11 0QX, Oxon, England..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    A statistical study of EMIC waves observed by Cluster: 1. Wave properties2014In: 2014 XXXITH URSI General Assembly And Scientific Symposium (URSI GRASS), 2014Conference paper (Refereed)
    Abstract [en]

    Electromagnetic ion cyclotron (EMIC) waves are an important mechanism for particle energization and losses inside the magnetosphere. In order to better understand the effects of these waves on particle dynamics, detailed information about the ellipticity, normal angle, energy propagation angle distributions, and local plasma parameters are required. Previous statistical studies have used in situ observations to investigate the distribution of these parameters in the L-MLT frame within a limited MLAT range. In this study, we present a statistical analysis of EMIC wave properties using ten years (2001-2010) of data from Cluster, totaling 17,987 minutes of wave activity. Due to the polar orbit of Cluster, we are able to investigate EMIC waves at all MLATs and MLTs. This allows us to further investigate the MLAT dependence of various wave properties inside different MLT sectors and further explore the effects of Shabansky orbits on EMIC wave generation and propagation. The current paper focuses on the wave occurrence distribution as well as the distribution of wave properties.

  • 8.
    Allen, R. C.
    et al.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Zhang, J. -C
    Kistler, L. M.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Spence, H. E.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Lin, R. -L
    Klecker, B.
    Max Planck Inst Extraterr Phys, D-85748 Garching, Germany..
    Dunlop, M. W.
    Rutherford Appleton Lab, Div Space Sci, Harwell, Oxon, England..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Jordanova, V. K.
    Los Alamos Natl Lab, Los Alamos, NM USA..
    A statistical study of EMIC waves observed by Cluster: 1. Wave properties2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 7, 5574-5592 p.Article in journal (Refereed)
    Abstract [en]

    Electromagnetic ion cyclotron (EMIC) waves are an important mechanism for particle energization and losses inside the magnetosphere. In order to better understand the effects of these waves on particle dynamics, detailed information about the occurrence rate, wave power, ellipticity, normal angle, energy propagation angle distributions, and local plasma parameters are required. Previous statistical studies have used in situ observations to investigate the distribution of these parameters in the magnetic local time versus L-shell (MLT-L) frame within a limited magnetic latitude (MLAT) range. In this study, we present a statistical analysis of EMIC wave properties using 10years (2001-2010) of data from Cluster, totaling 25,431min of wave activity. Due to the polar orbit of Cluster, we are able to investigate EMIC waves at all MLATs and MLTs. This allows us to further investigate the MLAT dependence of various wave properties inside different MLT sectors and further explore the effects of Shabansky orbits on EMIC wave generation and propagation. The statistical analysis is presented in two papers. This paper focuses on the wave occurrence distribution as well as the distribution of wave properties. The companion paper focuses on local plasma parameters during wave observations as well as wave generation proxies.

  • 9.
    Allen, R. C.
    et al.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA.;Univ New Hampshire, Dept Phys, Durham, NH 03824 USA.;Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX 78238 USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78249 USA..
    Zhang, J. -C
    Kistler, L. M.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA.;Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Spence, H. E.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA.;Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Lin, R. -L
    Klecker, B.
    Max Planck Inst Extraterr Phys, Garching, Germany..
    Dunlop, M. W.
    Rutherford Appleton Lab, SSTD, Div Space Sci, Didcot, Oxon, England..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Jordanova, V. K.
    Los Alamos Natl Lab, Los Alamos, NM USA..
    A statistical study of EMIC waves observed by Cluster: 2. Associated plasma conditions2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 7, 6458-6479 p.Article in journal (Refereed)
    Abstract [en]

    This is the second in a pair of papers discussing a statistical study of electromagnetic ion cyclotron (EMIC) waves detected during 10years (2001-2010) of Cluster observations. In the first paper, an analysis of EMIC wave properties (i.e., wave power, polarization, normal angle, and wave propagation angle) is presented in both the magnetic latitude (MLAT)-distance as well as magnetic local time (MLT)-L frames. This paper focuses on the distribution of EMIC wave-associated plasma conditions as well as two EMIC wave generation proxies (the electron plasma frequency to gyrofrequency ratio proxy and the linear theory proxy) in these same frames. Based on the distributions of hot H+ anisotropy, electron and hot H+ density measurements, hot H+ parallel plasma beta, and the calculated wave generation proxies, three source regions of EMIC waves appear to exist: (1) the well-known overlap between cold plasmaspheric or plume populations with hot anisotropic ring current populations in the postnoon to dusk MLT region; (2) regions all along the dayside magnetosphere at high L shells related to dayside magnetospheric compression and drift shell splitting; and (3) off-equator regions possibly associated with the Shabansky orbits in the dayside magnetosphere.

  • 10.
    Alm, L.
    et al.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Argall, M. R.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Torbert, R. B.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.;Southwest Res Inst, San Antonio, TX USA..
    Farrugia, C. J.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Russell, C. T.
    Univ Calif Los Angeles, IGPP EPSS, Los Angeles, CA USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, IGPP EPSS, Los Angeles, CA USA..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lindqvist, P. -A
    Marklund, G. T.
    KTH Royal Inst Technol, Stockholm, Sweden..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Shuster, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.;Univ Maryland, Coll Comp Math & Nat Sci, College Pk, MD 20742 USA..
    EDR signatures observed by MMS in the 16 October event presented in a 2-D parametric space2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 3, 3262-3276 p.Article in journal (Refereed)
    Abstract [en]

    We present a method for mapping the position of satellites relative to the X line using the measured B-L and B-N components of the magnetic field and apply it to the Magnetospheric multiscale (MMS) encounter with the electron diffusion region (EDR) which occurred on 13:07 UT on 16 October 2015. Mapping the data to our parametric space succeeds in capturing many of the signatures associated with magnetic reconnection and the electron diffusion region. This offers a method for determining where in the reconnection region the satellites were located. In addition, parametric mapping can also be used to present data from numerical simulations. This facilitates comparing data from simulations with data from in situ observations as one can avoid the complicated process using boundary motion analysis to determine the geometry of the reconnection region. In parametric space we can identify the EDR based on the collocation of several reconnection signatures, such as electron nongyrotropy, electron demagnetization, parallel electric fields, and energy dissipation. The EDR extends 2-3km in the normal direction and in excess of 20km in the tangential direction. It is clear that the EDR occurs on the magnetospheric side of the topological X line, which is expected in asymmetric reconnection. Furthermore, we can observe a north-south asymmetry, where the EDR occurs north of the peak in out-of-plane current, which may be due to the small but finite guide field.

  • 11. Amata, E.
    et al.
    Savin, S.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dunlop, M.
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marcucci, M. F.
    Fazakerley, A.
    Bogdanova, Y. V.
    Decreau, P. M. E.
    Rauch, J. L.
    Trotignon, J. G.
    Skalsky, A.
    Romanov, S.
    Buechner, J.
    Blecki, J.
    Reme, H.
    Experimental study of nonlinear interaction of plasma flow with charged thin current sheets: 1. Boundary structure and motion2006In: Nonlinear processes in geophysics, ISSN 1023-5809, E-ISSN 1607-7946, Vol. 13, no 4, 365-376 p.Article in journal (Refereed)
    Abstract [en]

    We study plasma transport at a thin magnetopause (MP), described hereafter as a thin current sheet (TCS), observed by Cluster at the southern cusp on 13 February 2001 around 20:01 UT. The Cluster observations generally agree with the predictions of the Gas Dynamic Convection Field (GDCF) model in the magnetosheath (MSH) up to the MSH boundary layer, where significant differences are seen. We find for the MP a normal roughly along the GSE x-axis, which implies a clear departure from the local average MP normal, a similar to 90 km thickness and an outward speed of 35 km/s. Two populations are identified in the MSH boundary layer: the first one roughly perpendicular to the MSH magnetic field, which we interpret as the "incident" MSH plasma, the second one mostly parallel to B. Just after the MP crossing a velocity jet is observed with a peak speed of 240 km/s, perpendicular to B, with M-A=3 and beta> 10 (peak value 23). The magnetic field clock angle rotates by 70 degrees across the MP. E-x is the main electric field component on both sides of the MP, displaying a bipolar signature, positive on the MSH side and negative on the opposite side, corresponding to a similar to 300 V electric potential jump across the TCS. The E x B velocity generally coincides with the perpendicular velocity measured by CIS; however, in the speed jet a difference between the two is observed, which suggests the need for an extra flow source. We propose that the MP TCS can act locally as an obstacle for low-energy ions (<350 eV), being transparent for ions with larger gyroradius. As a result, the penetration of plasma by finite gyroradius is considered as a possible source for the jet. The role of reconnection is briefly discussed. The electrodynamics of the TCS along with mass and momentum transfer across it are further discussed in the companion paper by Savin et al. (2006).

  • 12. Amm, O.
    et al.
    Aruliah, A.
    Buchert, Stephan C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fujii, R.
    Gjerloev, J. W.
    Ieda, A.
    Matsuo, T.
    Stolle, C.
    Vanhamaeki, H.
    Yoshikawa, A.
    Towards understanding the electrodynamics of the 3-dimensional high-latitude ionosphere: present and future2008In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, no 12, 3913-3932 p.Article, review/survey (Refereed)
    Abstract [en]

    Traditionally, due to observational constraints, ionospheric modelling and data analysis techniques have been devised either in one dimension (e. g. along a single radar beam), or in two dimensions (e. g. over a network of magnetometers). With new upcoming missions like the Swarm ionospheric multi-satellite project, or the EISCAT 3-D project, the time has come to take into account variations in all three dimensions simultaneously, as they occur in the real ionosphere. The link between ionospheric electrodynamics and the neutral atmosphere circulation which has gained increasing interest in the recent years also intrinsically requires a truly 3-dimensional (3-D) description. In this paper, we identify five major science questions that need to be addressed by 3-D ionospheric modelling and data analysis. We briefly review what proceedings in the young field of 3-D ionospheric electrodynamics have been made in the past to address these selected question, and we outline how these issues can be addressed in the future with additional observations and/or improved data analysis and simulation techniques. Throughout the paper, we limit the discussion to high-latitude and mesoscale ionospheric electrodynamics, and to directly data-driven (not statistical) data analysis.

  • 13.
    Andersson, L.
    et al.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Ergun, R. E.
    Univ Colorado, LASP, Boulder, CO 80309 USA.;Univ Colorado, APS, Boulder, CO 80309 USA..
    Delory, G. T.
    Univ Calif Berkeley, SSL, Berkeley, CA 94720 USA..
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Westfall, J.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Reed, H.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    McCauly, J.
    Univ Calif Berkeley, SSL, Berkeley, CA 94720 USA..
    Summers, D.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Meyers, D.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    The Langmuir Probe and Waves (LPW) Instrument for MAVEN2015In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 195, no 1-4, 173-198 p.Article, review/survey (Refereed)
    Abstract [en]

    We describe the sensors, the sensor biasing and control, the signal-processing unit, and the operation of the Langmuir Probe and Waves (LPW) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. The LPW instrument is designed to measure the electron density and temperature in the ionosphere of Mars and to measure spectral power density of waves (DC-2 MHz) in Mars' ionosphere, including one component of the electric field. Low-frequency plasma waves can heat ions resulting in atmospheric loss. Higher-frequency waves are used to calibrate the density measurement and to study strong plasma processes. The LPW is part of the Particle and Fields (PF) suite on the MAVEN spacecraft. The LPW instrument utilizes two, 40 cm long by 0.635 cm diameter cylindrical sensors with preamplifiers, which can be configured to measure either plasma currents or plasma waves. The sensors are mounted on a pair of meter long stacer booms. The sensors and nearby surfaces are controlled by a Boom Electronics Board (BEB). The Digital Fields Board (DFB) conditions the analog signals, converts the analog signals to digital, processes the digital signals including spectral analysis, and packetizes the data for transmission. The BEB and DFB are located inside of the Particle and Fields Digital Processing Unit (PFDPU).

  • 14. Andersson, L.
    et al.
    Ergun, R. E.
    Tao, J.
    Roux, A.
    LeContel, O.
    Angelopoulos, V.
    Bonnell, J.
    McFadden, J. P.
    Larson, D. E.
    Eriksson, S.
    Johansson, T.
    Cully, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Newman, D. N.
    Goldman, M. V.
    Glassmeier, K. -H
    Baumjohann, W.
    New Features of Electron Phase Space Holes Observed by the THEMIS Mission2009In: Physical Review Letters, ISSN 0031-9007, Vol. 102, no 22, 225004- p.Article in journal (Refereed)
    Abstract [en]

    Observations of electron phase-space holes (EHs) in Earth's plasma sheet by the THEMIS satellites include the first detection of a magnetic perturbation (delta B-parallel to) parallel to the ambient magnetic field (B-0). EHs with a detectable delta B-parallel to have several distinguishing features including large electric field amplitudes, a magnetic perturbation perpendicular to B-0, high speeds (similar to 0.3c) along B-0, and sizes along B-0 of tens of Debye lengths. These EHs have a significant center potential (Phi similar to k(B)T(e)/e), suggesting strongly nonlinear behavior nearby such as double layers or magnetic reconnection.

  • 15.
    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.

  • 16. Andreeova, K.
    et al.
    Pulkkinen, T. I.
    Laitinen, Tiera V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Prech, L.
    Shock propagation in the magnetosphere: Observations and MHD simulations compared2008In: Journal of Geophysical Research, ISSN 0148-0227, Vol. 113, no A9, A09224- p.Article in journal (Refereed)
    Abstract [en]

    We examine the propagation of disturbances in the Earth's magnetosphere caused by fast forward shock interaction with the magnetopause. Our statistical study and event analyses show that the propagation speeds are larger in the magnetosphere than in the solar wind and are larger in the nightside magnetosphere than in the dayside magnetosphere. A case study of a double shock during 9 November 2002 is examined both observationally and using the GUMICS-4 global MHD simulation. Tracing the disturbance propagation allows us to confirm that the MHD simulation results are in good agreement with the in situ observations. The simulation results show that the propagation of the disturbance occurs in the antisunward direction at all clock angles simultaneously. However, changes in the magnetosheath are largest at high latitudes, while in the magnetotail the largest variations are seen in the plasma sheet.

  • 17.
    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.

  • 18.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    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.

  • 22.
    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.

  • 23.
    Andriopoulou, M.
    et al.
    Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria..
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria..
    Torkar, K.
    Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria..
    Baumjohann, W.
    Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria..
    Torbert, R. B.
    Univ New Hampshire, Inst Study Earth Oceans & Space, Durham, NH 03824 USA..
    Lindqvist, P. -A
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dorelli, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Burch, J. L.
    SW Res Inst, San Antonio, TX USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Study of the spacecraft potential under active control and plasma density estimates during the MMS commissioning phase2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 10, 4858-4864 p.Article in journal (Refereed)
    Abstract [en]

    Each spacecraft of the recently launched magnetospheric multiscale MMS mission is equipped with Active Spacecraft Potential Control (ASPOC) instruments, which control the spacecraft potential in order to reduce spacecraft charging effects. ASPOC typically reduces the spacecraft potential to a few volts. On several occasions during the commissioning phase of the mission, the ASPOC instruments were operating only on one spacecraft at a time. Taking advantage of such intervals, we derive photoelectron curves and also perform reconstructions of the uncontrolled spacecraft potential for the spacecraft with active control and estimate the electron plasma density during those periods. We also establish the criteria under which our methods can be applied.

  • 24.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Previously hidden low-energy ions: a better map of near-Earth space and the terrestrial mass balance2015In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 90, no 12, 128005Article in journal (Refereed)
    Abstract [en]

    This is a review of the mass balance of planet Earth, intended also for scientists not usually working with space physics or geophysics. The discussion includes both outflow of ions and neutrals from the ionosphere and upper atmosphere, and the inflow of meteoroids and larger objects. The focus is on ions with energies less than tens of eV originating from the ionosphere. Positive low-energy ions are complicated to detect onboard sunlit spacecraft at higher altitudes, which often become positively charged to several tens of volts. We have invented a technique to observe low-energy ions based on the detection of the wake behind a charged spacecraft in a supersonic ion flow. We find that low-energy ions usually dominate the ion density and the outward flux in large volumes in the magnetosphere. The global outflow is of the order of 10(26) ions s(-1). This is a significant fraction of the total number outflow of particles from Earth, and changes plasma processes in near-Earth space. We compare order of magnitude estimates of the mass outflow and inflow for planet Earth and find that they are similar, at around 1 kg s(-1) (30 000 ton yr(-1)). We briefly discuss atmospheric and ionospheric outflow from other planets and the connection to evolution of extraterrestrial life.

  • 25.
    André, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cully, Christopher M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Low-energy ions: A previously hidden solar system particle population2012In: Geophysical Research Letters, ISSN 0094-8276, Vol. 39, L03101- p.Article in journal (Refereed)
    Abstract [en]

    Ions with energies less than tens of eV originate from the Terrestrial ionosphere and from several planets and moons in the solar system. The low energy indicates the origin of the plasma but also severely complicates detection of the positive ions onboard sunlit spacecraft at higher altitudes, which often become positively charged to several tens of Volts. We discuss some methods to observe low-energy ions, including a recently developed technique based on the detection of the wake behind a charged spacecraft in a supersonic flow. Recent results from this technique show that low-energy ions typically dominate the density in large regions of the Terrestrial magnetosphere on the nightside and in the polar regions. These ions also often dominate in the dayside magnetosphere, and can change the dynamics of processes like magnetic reconnection. The loss of this low-energy plasma to the solar wind is one of the primary pathways for atmospheric escape from planets in our solar system. We combine several observations to estimate how common low-energy ions are in the Terrestrial magnetosphere and briefly compare with Mars, Venus and Titan.

  • 26.
    André, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Li, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Outflow of low-energy ions and the solar cycle2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 2, 1072-1085 p.Article in journal (Refereed)
    Abstract [en]

    Magnetospheric ions with energies less than tens of eV originate from the ionosphere. Positive low-energy ions are complicated to detect onboard sunlit spacecraft at higher altitudes, which often become positively charged to several tens of volts. We use two Cluster spacecraft and study low-energy ions with a technique based on the detection of the wake behind a charged spacecraft in a supersonic ion flow. We find that low-energy ions usually dominate the density and the outward flux in the geomagnetic tail lobes during all parts of the solar cycle. The global outflow is of the order of 10(26) ions/s and often dominates over the outflow at higher energies. The outflow increases by a factor of 2 with increasing solar EUV flux during a solar cycle. This increase is mainly due to the increased density of the outflowing population, while the outflow velocity does not vary much. Thus, the outflow is limited by the available density in the ionospheric source rather than by the energy available in the magnetosphere to increase the velocity.

  • 27.
    André, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Li, Wenya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Toledo-Redondo, S.
    European Space Agcy ESAC, Madrid, Spain..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Norgren, Cecilia
    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.
    Burch, J.
    Southwest Res Inst, San Antonio, TX USA..
    Lindqvist, P. -A
    KTH, Stockholm, Sweden.
    Marklund, G.
    KTH, Stockholm, Sweden..
    Ergun, R.
    Univ Colorado, LASP, Boulder, CO 80309 USA..
    Torbert, R.
    Southwest Res Inst, San Antonio, TX USA.;Univ New Hampshire, Durham, NH 03824 USA..
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA..
    Giles, B.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Moore, T. E.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Chandler, M. O.
    NASA, Marshall Space Flight Ctr, Huntsville, AL USA..
    Pollock, C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Young, D. T.
    Southwest Res Inst, San Antonio, TX USA..
    Avanov, L. A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.;Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, Toulouse, France.;CNRS, UMR 5277, Toulouse, France..
    Saito, Y.
    Inst Space & Astronaut Sci, JAXA, Chofu, Tokyo, Japan..
    Magnetic reconnection and modification of the Hall physics due to cold ions at the magnetopause2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 13, 6705-6712 p.Article in journal (Refereed)
    Abstract [en]

    Observations by the four Magnetospheric Multiscale spacecraft are used to investigate the Hall physics of a magnetopause magnetic reconnection separatrix layer. Inside this layer of currents and strong normal electric fields, cold (eV) ions of ionospheric origin can remain frozen-in together with the electrons. The cold ions reduce the Hall current. Using a generalized Ohm's law, the electric field is balanced by the sum of the terms corresponding to the Hall current, the vxB drifting cold ions, and the divergence of the electron pressure tensor. A mixture of hot and cold ions is common at the subsolar magnetopause. A mixture of length scales caused by a mixture of ion temperatures has significant effects on the Hall physics of magnetic reconnection.

  • 28.
    André, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yu V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Laitinen, Tiera V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Nilsson, H.
    Stenberg, G.
    Fazakerley, A.
    Trotignon, J. G.
    Magnetic reconnection and cold plasma at the magnetopause2010In: Geophysical Research Letters, ISSN 0094-8276, Vol. 37, no 22, L22108- p.Article in journal (Refereed)
    Abstract [en]

    We report on detailed observations by the four Cluster spacecraft of magnetic reconnection and a Flux Transfer Event (FTE) at the magnetopause. We detect cold (eV) plasma at the magnetopause with two independent methods. We show that the cold ions can be essential for the electric field normal to the current sheet in the separatrix region at the edge of the FTE and for the associated acceleration of ions from the magnetosphere into the reconnection jet. The cold ions have small enough gyroradii to drift inside the limited separatrix region and the normal electric field can be balanced by this drift, E approximate to -v x B. The separatrix region also includes cold accelerated electrons, as part of the reconnection current circuit.

  • 29. Angelopoulos, V.
    et al.
    Sibeck, D.
    Carlson, C. W.
    McFadden, J. P.
    Larson, D.
    Lin, R. P.
    Bonnell, J. W.
    Mozer, F. S.
    Ergun, R.
    Cully, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Glassmeier, K. H.
    Auster, U.
    Roux, A.
    LeContel, O.
    Frey, S.
    Phan, T.
    Mende, S.
    Frey, H.
    Donovan, E.
    Russell, C. T.
    Strangeway, R.
    Liu, J.
    Mann, I.
    Rae, I. J.
    Raeder, J.
    Li, X.
    Liu, W.
    Singer, H. J.
    Sergeev, V. A.
    Apatenkov, S.
    Parks, G.
    Fillingim, M.
    Sigwarth, J.
    First Results from the THEMIS Mission2008In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 141, no 1-4, 453-476 p.Article, review/survey (Refereed)
    Abstract [en]

    THEMIS was launched on February 17, 2007 to determine the trigger and large-scale evolution of substorms. During the first seven months of the mission the five satellites coasted near their injection orbit to avoid differential precession in anticipation of orbit placement, which started in September 2007 and led to a commencement of the baseline mission in December 2007. During the coast phase the probes were put into a string-of-pearls configuration at 100 s of km to 2 R-E along-track separations, which provided a unique view of the magnetosphere and enabled an unprecedented dataset in anticipation of the first tail season. In this paper we describe the first THEMIS substorm observations, captured during instrument commissioning on March 23, 2007. THEMIS measured the rapid expansion of the plasma sheet at a speed that is commensurate with the simultaneous expansion of the auroras on the ground. These are the first unequivocal observations of the rapid westward expansion process in space and on the ground. Aided by the remote sensing technique at energetic particle boundaries and combined with ancillary measurements and MHD simulations, they allow determination and mapping of space currents. These measurements show the power of the THEMIS instrumentation in the tail and the radiation belts. We also present THEMIS Flux Transfer Events (FTE) observations at the magnetopause, which demonstrate the importance of multi-point observations there and the quality of the THEMIS instrumentation in that region of space.

  • 30. Apatenkov, S. V.
    et al.
    Sergeev, V. A.
    Amm, O.
    Baumjohann, W.
    Nakamura, R.
    Runov, A.
    Rich, F.
    Daly, P.
    Fazakerley, A.
    Alexeev, I.
    Sauvaud, J. A.
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Conjugate observation of sharp dynamical boundary in the inner magnetosphere by Cluster and DMSP spacecraft and ground network2008In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, no 9, 2771-2780 p.Article in journal (Refereed)
    Abstract [en]

    We investigate an unusual sharp boundary separating two plasma populations (inner magnetospheric plasma with high fluxes of energetic particles and plasma sheet) observed by the Cluster quartet near its perigee on 16 December 2003. Cluster was in a pearl-on-string configuration at 05:00 MLT and mapped along magnetic field lines to similar to 8-9 R-E in the equatorial plane. It was conjugate to the MIRACLE network and the DMSP F16 spacecraft passed close to Cluster footpoint. The properties of the sharp boundary, repeatedly crossed 7 times by five spacecraft during similar to 10 min, are: (1) upward FAC sheet at the boundary with similar to 30 nA/m(2) current density at Cluster and similar to 2000 nA/m(2) at DMSP; (2) the boundary had an embedded layered structure with different thickness scales, the electron population transition was at similar to 20 km scale at Cluster (<7 km at DMSP), proton population had a scale similar to 100 km, while the FAC sheet thickness was estimated to be similar to 500 km at Cluster (similar to 100 km at DMSP); (3) the boundary propagated in the earthward-eastward direction at similar to 8 km/s in situ (equatorward-eastward similar to 0.8 km/s in ionosphere), and then decelerated and/or stopped. We discuss the boundary formation by the collision of two different plasmas which may include dynamical three-dimensional field-aligned current loops.

  • 31. Apatenkov, S. V.
    et al.
    Sergeev, V. A.
    Kubyshkina, M. V.
    Nakamura, R.
    Baumjohann, W.
    Runov, A.
    Alexeev, I.
    Fazakerley, A.
    Frey, H.
    Muhlbachler, S.
    Daly, P. W.
    Sauvaud, J. -A
    Ganushkina, N.
    Pulkkinen, T.
    Reeves, G. D.
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Multi-spacecraft observation of plasma dipolarization/injection in the inner magnetosphere2007In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 25, no 3, 801-814 p.Article in journal (Refereed)
    Abstract [en]

    Addressing the origin of the energetic particle injections into the inner magnetosphere, we investigate the 23 February 2004 substorm using a favorable constellation of four Cluster (near perigee), LANL and Geotail spacecraft. Both an energy-dispersed and a dispersionless injection were observed by Cluster crossing the plasma sheet horn, which mapped to 9-12 R-E in the equatorial plane close to the midnight meridian. Two associated narrow equatorward auroral tongues/streamers propagating from the oval poleward boundary could be discerned in the global images obtained by IMAGE/WIC. As compared to the energy-dispersed event, the dispersionless injection front has important distinctions consequently repeated at 4 spacecraft: a simultaneous increase in electron fluxes at energies similar to 1.300 keV, similar to 25 nT increase in B-Z and a local increase by a factor 1.5-1.7 in plasma pressure. The injected plasma was primarily of solar wind origin. We evaluated the change in the injected flux tube configuration during the dipolarization by fitting flux increases observed by the PEACE and RAPID instruments, assuming adiabatic heating and the Liouville theorem. Mapping the locations of the injection front detected by the four spacecraft to the equatorial plane, we estimated the injection front thickness to be similar to 1 R-E and the earthward propagation speed to be similar to 200-400km/s (at 9-12 RE). Based on observed injection properties, we suggest that it is the underpopulated flux tubes (bubbles with enhanced magnetic field and sharp inner front propagating earthward), which accelerate and transport particles into the strong-field dipolar region.

  • 32. Arridge, Christopher S.
    et al.
    Agnor, Craig B.
    Andre, Nicolas
    Baines, Kevin H.
    Fletcher, Leigh N.
    Gautier, Daniel
    Hofstadter, Mark D.
    Jones, Geraint H.
    Lamy, Laurent
    Langevin, Yves
    Mousis, Olivier
    Nettelmann, Nadine
    Russell, Christopher T.
    Stallard, Tom
    Tiscareno, Matthew S.
    Tobie, Gabriel
    Bacon, Andrew
    Chaloner, Chris
    Guest, Michael
    Kemble, Steve
    Peacocke, Lisa
    Achilleos, Nicholas
    Andert, Thomas P.
    Banfield, Don
    Barabash, Stas
    Barthelemy, Mathieu
    Bertucci, Cesar
    Brandt, Pontus
    Cecconi, Baptiste
    Chakrabarti, Supriya
    Cheng, Andy F.
    Christensen, Ulrich
    Christou, Apostolos
    Coates, Andrew J.
    Collinson, Glyn
    Cooper, John F.
    Courtin, Regis
    Dougherty, Michele K.
    Ebert, Robert W.
    Entradas, Marta
    Fazakerley, Andrew N.
    Fortney, Jonathan J.
    Galand, Marina
    Gustin, Jaques
    Hedman, Matthew
    Helled, Ravit
    Henri, Pierre
    Hess, Sebastien
    Holme, Richard
    Karatekin, Ozgur
    Krupp, Norbert
    Leisner, Jared
    Martin-Torres, Javier
    Masters, Adam
    Melin, Henrik
    Miller, Steve
    Mueller-Wodarg, Ingo
    Noyelles, Benoit
    Paranicas, Chris
    de Pater, Imke
    Paetzold, Martin
    Prange, Renee
    Quemerais, Eric
    Roussos, Elias
    Rymer, Abigail M.
    Sanchez-Lavega, Agustin
    Saur, Joachim
    Sayanagi, Kunio M.
    Schenk, Paul
    Schubert, Gerald
    Sergis, Nick
    Sohl, Frank
    Sittler, Edward C., Jr.
    Teanby, Nick A.
    Tellmann, Silvia
    Turtle, Elizabeth P.
    Vinatier, Sandrine
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Zarka, Philippe
    Uranus Pathfinder: exploring the origins and evolution of Ice Giant planets2012In: Experimental astronomy (Print), ISSN 0922-6435, E-ISSN 1572-9508, Vol. 33, no 2-3, 753-791 p.Article in journal (Refereed)
    Abstract [en]

    The "Ice Giants" Uranus and Neptune are a different class of planet compared to Jupiter and Saturn. Studying these objects is important for furthering our understanding of the formation and evolution of the planets, and unravelling the fundamental physical and chemical processes in the Solar System. The importance of filling these gaps in our knowledge of the Solar System is particularly acute when trying to apply our understanding to the numerous planetary systems that have been discovered around other stars. The Uranus Pathfinder (UP) mission thus represents the quintessential aspects of the objectives of the European planetary community as expressed in ESA's Cosmic Vision 2015-2025. UP was proposed to the European Space Agency's M3 call for medium-class missions in 2010 and proposed to be the first orbiter of an Ice Giant planet. As the most accessible Ice Giant within the M-class mission envelope Uranus was identified as the mission target. Although not selected for this call the UP mission concept provides a baseline framework for the exploration of Uranus with existing low-cost platforms and underlines the need to develop power sources suitable for the outer Solar System. The UP science case is based around exploring the origins, evolution, and processes at work in Ice Giant planetary systems. Three broad themes were identified: (1) Uranus as an Ice Giant, (2) An Ice Giant planetary system, and (3) An asymmetric magnetosphere. Due to the long interplanetary transfer from Earth to Uranus a significant cruise-phase science theme was also developed. The UP mission concept calls for the use of a Mars Express/Rosetta-type platform to launch on a Soyuz-Fregat in 2021 and entering into an eccentric polar orbit around Uranus in the 2036-2037 timeframe. The science payload has a strong heritage in Europe and beyond and requires no significant technology developments.

  • 33. Aunai, N.
    et al.
    Retino, A.
    Belmont, G.
    Smets, R.
    Lavraud, B.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    The proton pressure tensor as a new proxy of the proton decoupling region in collisionless magnetic reconnection2011In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 29, no 9, 1571-1579 p.Article in journal (Refereed)
    Abstract [en]

    Cluster data is analyzed to test the proton pressure tensor variations as a proxy of the proton decoupling region in collisionless magnetic reconnection. The Hall electric potential well created in the proton decoupling region results in bounce trajectories of the protons which appears as a characteristic variation of one of the in-plane off-diagonal components of the proton pressure tensor in this region. The event studied in this paper is found to be consistent with classical Hall field signatures with a possible 20% guide field. Moreover, correlations between this pressure tensor component, magnetic field and bulk flow are proposed and validated, together with the expected counterstreaming proton distribution functions.

  • 34.
    Backrud, Marie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Tjulin, Anders
    Vaivads, Andris
    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, Department of Astronomy and Space Physics.
    Fazakerley, Andrew
    Interferometric Identification of Ion Acoustic Broadband Waves in the Auroral Region: CLUSTER Observations2005In: Geophysical Research Letters, ISSN 0094-8276, Vol. 32, no 21Article in journal (Refereed)
    Abstract [en]

    [1] We determine the phase velocity and k vector for parallel and oblique broadband extremely low frequency, ELF, waves on nightside auroral magnetic field lines at altitudes around 4.6 RE. We use internal burst mode data from the EFW electric field and wave instrument onboard the Cluster spacecraft to retrieve phase differences between the four probes of the instrument. The retrieved characteristic phase velocity is of the order of the ion acoustic speed and larger than the thermal velocity of the protons. The typical wavelength obtained from interferometry is around the proton gyro radius and always larger than the Debye length. We find that in regions with essentially no suprathermal electrons above a few tens of eV the observed broadband waves above the proton gyro frequency are consistent with upgoing ion acoustic and oblique ion acoustic waves.

  • 35.
    Backrud-Ivgren, Marie
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Stenberg, Gabriella
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morooka, Michiko
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Hobara, Yasuhide
    Joko, Sachiko
    Rönnmark, Kjell
    Cornilleau-Wehrlin, Nicole
    Fazakerley, Andrew
    Rème, Henri
    Cluster observations and theoretical identification of broadband waves in the auroral region2005In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 23, no 12, 3739-3752 p.Article in journal (Refereed)
    Abstract [en]

    Broadband waves are common on auroral field lines. We use two different methods to study the polarization of the waves at 10 to 180 Hz observed by the Cluster spacecraft at altitudes of about 4 Earth radii in the nightside auroral region. Observations of electric and magnetic wave fields, together with electron and ion data, are used as input to the methods. We find that much of the wave emissions are consistent with linear waves in homogeneous plasma. Observed waves with a large electric field perpendicular to the geomagnetic field are more common (electrostatic ion cyclotron waves), while ion acoustic waves with a large parallel electric field appear in smaller regions without suprathermal (tens of eV) plasma. The regions void of suprathermal plasma are interpreted as parallel potential drops of a few hundred volts.

  • 36.
    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.

  • 37.
    Bale, S. D.
    et al.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA..
    Goetz, K.
    Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA..
    Harvey, P. R.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Turin, P.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Bonnell, J. W.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Dudok de Wit, T.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    MacDowall, R. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Pulupa, M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Bolton, M.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Bougeret, J. -L
    Bowen, T. A.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA..
    Burgess, D.
    Queen Mary Univ London, Astron Unit, London, England..
    Cattell, C. A.
    Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA..
    Chandran, B. D. G.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Chaston, C. C.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Chen, C. H. K.
    Imperial Coll, Dept Phys, London, England..
    Choi, M. K.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Connerney, J. E.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Cranmer, S.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Diaz-Aguado, M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Donakowski, W.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Drake, J. F.
    Univ Maryland, Dept Phys, College Pk, MD 20742 USA..
    Farrell, W. M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Fergeau, P.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Fermin, J.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Fischer, J.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Fox, N.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Glaser, D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Goldstein, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gordon, D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Hanson, E.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA..
    Harris, S. E.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Hayes, L. M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Hinze, J. J.
    Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA..
    Hollweg, J. V.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Horbury, T. S.
    Imperial Coll, Dept Phys, London, England..
    Howard, R. A.
    Naval Res Lab, Washington, DC 20375 USA..
    Hoxie, V.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Jannet, G.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Karlsson, M.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Kasper, J. C.
    Univ Michigan, Ann Arbor, MI 48109 USA..
    Kellogg, P. J.
    Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA..
    Kien, M.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Klimchuk, J. A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Krasnoselskikh, V. V.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Krucker, S.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Lynch, J. J.
    Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA..
    Maksimovic, M.
    Observ Paris, LESIA, Meudon, France..
    Malaspina, D. M.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Marker, S.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Martin, P.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Martinez-Oliveros, J.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    McCauley, J.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    McComas, D. J.
    Southwest Res Inst, San Antonio, TX USA..
    McDonald, T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Meyer-Vernet, N.
    Observ Paris, LESIA, Meudon, France..
    Moncuquet, M.
    Observ Paris, LESIA, Meudon, France..
    Monson, S. J.
    Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA..
    Mozer, F. S.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Murphy, S. D.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Odom, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Oliverson, R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Olson, J.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Parker, E. N.
    Univ Chicago, Dept Astron & Astrophys, 5640 S Ellis Ave, Chicago, IL 60637 USA..
    Pankow, D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Phan, T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Quataert, E.
    Univ Calif Berkeley, Dept Astron, 601 Campbell Hall, Berkeley, CA 94720 USA..
    Quinn, T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Ruplin, S. W.
    Praxis Studios, Brooklyn, NY USA..
    Salem, C.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Seitz, D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Sheppard, D. A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Siy, A.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Stevens, K.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Summers, D.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Szabo, A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Timofeeva, M.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Velli, M.
    UCLA, Earth Planetary & Space Sci, Los Angeles, CA USA..
    Yehle, A.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO USA..
    Werthimer, D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Wygant, J. R.
    Univ Minnesota, Sch Phys & Astron, Minneapolis, MN 55455 USA..
    The FIELDS Instrument Suite for Solar Probe Plus2016In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 204, no 1-4, 49-82 p.Article, review/survey (Refereed)
    Abstract [en]

    NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.

  • 38. Baumjohann, W.
    et al.
    Roux, A.
    Le Contel, O.
    Nakamura, R.
    Birn, J.
    Hoshino, M.
    Lui, A. T. Y.
    Owen, C. J.
    Sauvaud, J. -A
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fontaine, D.
    Runov, A.
    Dynamics of thin current sheets: Cluster observations2007In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 25, no 6, 1365-1389 p.Article, review/survey (Refereed)
    Abstract [en]

    The paper tries to sort out the specific signatures of the Near Earth Neutral Line (NENL) and the Current Disruption (CD) models. and looks for these signatures in Cluster data from two events. For both events transient magnetic si-natures are observed, together with fast ion flows. In the simplest form of NENL scenario, with a large-scale two-dimensional reconnection site, quasi-invariance along Y is expected. Thus the magnetic signatures in the S/C frame are interpreted as relative motions, along the X or Z direction, of a quasi-steady X-line, with respect to the S/C. In the simplest form of CD scenario an azimuthal modulation is expected. Hence the signatures in the S/C frame are interpreted as signatures of azimuthally (along Y) moving current system associated with low frequency fluctuations of J(y) and the corresponding field-aligned currents Event I covers a pseudo-breakup, developing only at high latitudes. First, a thin (H approximate to 2000Km approximate to 2 rho(i), with pi the ion gyroradius) Current Sheet (CS) is found to be quiet. A slightly thinner CS (H approximate to 1000-2000 km approximate to 1-2 rho(i)), crossed about 30 min later, is found to be active. with fast earthward ion flow bursts (300-600 km/s) and simultaneous large amplitude fluctuations (delta B/B similar to 1). In the quiet CS the current density J(y) is carried by ions. Conversely, in the active CS ions are moving eastward; the westward current is carried by electrons that move eastward, faster than ions. Similarly, the velocity of earthward flows (300-600 km/s), observed during the active period. maximizes near or at the CS center. During the active phase of Event I no signature of the crossing of an X-line is identified, but an X-line located beyond Cluster could account for the observed ion flows, provided that it is active for at least 20 min. Ion flow bursts can also be due to CD and to the corresponding dipolarizations which are associated with changes in the current density. Yet their durations are shorter than the duration of the active period. While the overall partial derivative Bz/partial derivative t is too weak to accelerate ions up to the observed velocities, short duration partial derivative B-z/partial derivative t can produce the azimuthal electric field requested to account for the observed ion flow bursts. The corresponding large amplitude perturbations are shown to move eastward. which suggests that the reduction in the tail current could be achieved via a series of eastward traveling partial dipolarisations/CD. The second event is much more active than the first one. The observed flapping of the CS corresponds to an azimuthally propagating wave. A reversal in the proton flow velocity, from 1000 to + 1000 km/s, is measured by CODIF. The overall flow reversal, the associated change in the sign of B-z and the relationship between B-x and B-y suggest that the spacecraft are moving with respect to an X-line and its associated Hall-structure. Yet, a simple tailward retreat of a large-scale X-line cannot account for all the observations, since several flow reversals are observed. These quasi-periodic flow reversals can also be associated with an azimuthal motion of the low frequency oscillations. Indeed, at the beginning of the interval B-y varies rapidly along the Y direction; the magnetic signature is three-dimensional and essentially corresponds to a structure of filamentary field-aligned current, moving eastward at similar to 200 km/s. The transverse size of the structure is similar to 1000 km. Similar structures are observed before and after. Thesefilamentary structures are consistent with an eastward propagation of an azimuthal modulation associated with a current system J(y), J(x). During Event 1, signatures of filamentary field-aligned current structures are also observed, in association with modulations of J(y). Hence, for both events the structure of the magnetic fields and currents is three-dimensional.

  • 39. Bavassano Cattaneo, M. Bice
    et al.
    Marcucci, M. Federica
    Retinò, Alessandro
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Pallocchia, G.
    Rème, H.
    Dandouras, I.
    Kistler, L. M.
    Klecker, B.
    Carlson, C. W.
    Korth, A.
    McCarthy, M.
    Lundin, Rickard
    Balogh, A.
    Kinetic signatures during a quasi-continuous lobe reconnection event: Cluster Ion Spectrometer (CIS) observations2006In: Journal of Geophysical Research, ISSN 0148-0227, Vol. 111, no A9, A09212- p.Article in journal (Refereed)
    Abstract [en]

    On 3 December 2001 the Cluster spacecraft observed a long-lasting lobe reconnection event in the southern high-latitude dusk magnetopause (MP) tailward of the cusp, during a 4 hour interval of mainly northward interplanetary magnetic field ( IMF) and of sub-Alfvenic magnetosheath flow. Almost all the MP encounters have accelerated flows ( for which the Walen test has been successfully verified by Retino et al. ( 2005)) as well as a large number of secondary populations related to reconnection, that is, ions of magnetosheath or magnetospheric origin which cross the MP either way. The detailed analysis of the distribution functions shows that the reconnection site frequently moves relative to the spacecraft, but simultaneous measurements by two spacecraft on opposite sides of the reconnection site indicate that the spacecraft's distance from the X line is small, i.e., below 3200 km. The vicinity to the X line throughout the event is probably the reason why the distribution functions characteristics agree with theoretical expectations on both sides of the reconnection site throughout this long event. Moreover, the detailed analysis of the distribution functions shows evidence, during a few time intervals, of dual reconnection, i.e., of reconnection simultaneously going on also in the northern hemisphere.

  • 40. Berthomier, M.
    et al.
    Fazakerley, A. N.
    Forsyth, C.
    Pottelette, R.
    Alexandrova, O.
    Anastasiadis, A.
    Aruliah, A.
    Blelly, P. -L
    Briand, C.
    Bruno, R.
    Canu, P.
    Cecconi, B.
    Chust, T.
    Daglis, I.
    Davies, J.
    Dunlop, M.
    Fontaine, D.
    Genot, V.
    Gustavsson, B.
    Haerendel, G.
    Hamrin, M.
    Hapgood, M.
    Hess, S.
    Kataria, D.
    Kauristie, K.
    Kemble, S.
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Koskinen, H.
    Lamy, L.
    Lanchester, B.
    Louarn, P.
    Lucek, E.
    Lundin, R.
    Maksimovic, M.
    Manninen, J.
    Marchaudon, A.
    Marghitu, O.
    Marklund, G.
    Milan, S.
    Moen, J.
    Mottez, F.
    Nilsson, H.
    Ostgaard, N.
    Owen, C. J.
    Parrot, M.
    Pedersen, A.
    Perry, C.
    Pincon, J. -L
    Pitout, F.
    Pulkkinen, T.
    Rae, I. J.
    Rezeau, L.
    Roux, A.
    Sandahl, I.
    Sandberg, I.
    Turunen, E.
    Vogt, J.
    Walsh, A.
    Watt, C. E. J.
    Wild, J. A.
    Yamauchi, M.
    Zarka, P.
    Zouganelis, I.
    Alfven: magnetosphere-ionosphere connection explorers2012In: Experimental astronomy (Print), ISSN 0922-6435, E-ISSN 1572-9508, Vol. 33, no 2-3, 445-489 p.Article in journal (Refereed)
    Abstract [en]

    The aurorae are dynamic, luminous displays that grace the night skies of Earth's high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the ionospheric environment at the top of Earth's atmosphere play a central role. In this Auroral Acceleration Region (AAR) persistent electric fields directed along the magnetic field accelerate magnetospheric electrons to the high energies needed to excite luminosity when they hit the atmosphere. The "ideal magnetohydrodynamics" description of space plasmas which is useful in much of the magnetosphere cannot be used to understand the AAR. The AAR has been studied by a small number of single spacecraft missions which revealed an environment rich in wave-particle interactions, plasma turbulence, and nonlinear acceleration processes, acting on a variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster magnetospheric research mission is now fortuitously visiting the AAR, but its particle instruments are too slow to allow resolve many of the key plasma physics phenomena. The Alfv,n concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planets.

  • 41. Bertucci, C.
    et al.
    Achilleos, N.
    Dougherty, M. K.
    Modolo, R.
    Coates, A. J.
    Szego, K.
    Masters, A.
    Ma, Y.
    Neubauer, F. M.
    Garnier, P.
    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.
    Young, D. T.
    The magnetic memory of Titan's ionized atmosphere2008In: Science, ISSN 0036-8075, Vol. 321, no 5895, 1475-1478 p.Article in journal (Refereed)
    Abstract [en]

    After 3 years and 31 close flybys of Titan by the Cassini Orbiter, Titan was finally observed in the shocked solar wind, outside of Saturn's magnetosphere. These observations revealed that Titan's flow- induced magnetosphere was populated by "fossil" fields originating from Saturn, to which the satellite was exposed before its excursion through the magnetopause. In addition, strong magnetic shear observed at the edge of Titan's induced magnetosphere suggests that reconnection may have been involved in the replacement of the fossil fields by the interplanetary magnetic field.

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

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

  • 43. Bertucci, C.
    et al.
    Neubauer, F. M.
    Szego, K.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Coates, A. J.
    Dougherty, M. K.
    Young, D. T.
    Kurth, W. S.
    Structure of Titan's mid-range magnetic tail: Cassini magnetometer observations during the T9 flyby2007In: Geophysical Research Letters, ISSN 0094-8276, Vol. 34, no 24, L24S02- p.Article in journal (Refereed)
    Abstract [en]

    We analyze the magnetic structure of Titan's mid-range magnetic tail (5-6 Titan radii downstream from the moon) during Cassini's T9 flyby. Cassini magnetometer (MAG) measurements reveal a well-defined, induced magnetic tail consisting of two lobes and a distinct central current sheet. MAG observations also indicate that Saturn's background magnetic field is close to the moon's orbital plane and that the magnetospheric flow has a significant component in the Saturn-Titan direction. The analysis of MAG data in a coordinate system based on the orientation of the background magnetic field and an estimation of the incoming flow direction suggests that Titan's magnetic tail is extremely asymmetric. An important source of these asymmetries is the connection of the inbound tail lobe and the outbound tail lobe to the dayside and nightside hemispheres of Titan, respectively. Another source could be the perturbations generated by changes in the upstream conditions.

  • 44.
    Beth, A.
    et al.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Altwegg, K.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Balsiger, H.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Berthelier, J. -J
    Calmonte, U.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Combi, M. R.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, 2455 Hayward, Ann Arbor, MI 48109 USA..
    De Keyser, J.
    Royal Belgian Inst Space Aeron, BIRA, IASB, Ringlaan 3, B-1180 Brussels, Belgium..
    Dhooghe, F.
    Royal Belgian Inst Space Aeron, BIRA, IASB, Ringlaan 3, B-1180 Brussels, Belgium..
    Fiethe, B.
    TU Braunschweig, Inst Comp & Network Engn IDA, Hans Sommer Str 66, D-38106 Braunschweig, Germany..
    Fuselier, S. A.
    Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78228 USA.;Southwest Res Inst San Antonio, San Antonio, TX 78228 USA..
    Galand, M.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Gasc, S.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Gombosi, T. I.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, 2455 Hayward, Ann Arbor, MI 48109 USA..
    Hansen, K. C.
    Univ Michigan, Dept Atmospher Ocean & Space Sci, 2455 Hayward, Ann Arbor, MI 48109 USA..
    Hassig, M.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78228 USA..
    Heritier, K. L.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Kopp, E.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Le Roy, L.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Mandt, K. E.
    Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX 78228 USA.;Southwest Res Inst San Antonio, San Antonio, TX 78228 USA..
    Peroy, S.
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Rubin, M.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Semon, T.
    Univ Bern, Phys Inst, CH-3012 Bern, Switzerland..
    Tzou, C. -Y
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    First in situ detection of the cometary ammonium ion NH4+ (protonated ammonia NH3) in the coma of 67P/C-G near perihelion2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 462, S562-S572 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we report the first in situ detection of the ammonium ion NH4+ at 67P/Churyumov-Gerasimenko (67P/C-G) in a cometary coma, using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)/Double Focusing Mass Spectrometer (DFMS). Unlike neutral and ion spectrometers onboard previous cometary missions, the ROSINA/DFMS spectrometer, when operated in ion mode, offers the capability to distinguish NH4+ from H2O+ in a cometary coma. We present here the ion data analysis of mass-to-charge ratios 18 and 19 at high spectral resolution and compare the results with an ionospheric model to put these results into context. The model confirms that the ammonium ion NH4+ is one of the most abundant ion species, as predicted, in the coma near perihelion.

  • 45. Blagoveshchenskaya, N. F.
    et al.
    Borlsova, T. D.
    Kornienko, V. A.
    Leyser, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Rietveld, M. T.
    Thidé, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Artificial field-aligned irregularities in the nightside auroral ionosphere2006In: Advances in Space Research, ISSN 0273-1177, Vol. 38, no 11, 2503-2510 p.Article in journal (Refereed)
    Abstract [en]

    Experimental results from two Tromso HF heating experiments in the nightside high latitudinal F region are examined. Bi-static scatter measurements of HF diagnostic signals were carried out on the London-Tromso-St. Petersburg and Pori-Tromso-St. Petersburg paths using a Doppler spectral method. The properties and behaviour of artificial field-aligned small-scale irregularities (striations) in the nightside high latitudinal F-region in course of the Tromso ionospheric modification experiments are studied. Experimental studies have been performed by the use of phased array I with a beamwidth of 6 degrees instead of 12-14 degrees in phased array 2, more often used in Tromso ionospheric modification experiments. The comparison between two experiments carried out in the same background geophysical conditions, shows the strongest striations in the field-aligned position of the heater beam. Possible explanation for this angular dependence is self-focusing of HF pump waves on striations causing the energy to be distributed asymmetrically. A principal question related to HF heating experiments is how is the disturbed auroral ionosphere modified. The results obtained on two paths simultaneously have shown that the strong heater-induced striations were observed along with natural ones. Velocities of heater-induced striations were quite different at different parts of the heated volume. It is suggested that the heater-induced striations can be grouped in two patches at different heights possibly due to the temperature-gradient-driven instability.

  • 46. Blagoveshchenskaya, N. F.
    et al.
    Kornienko, V. A.
    Borisova, T. D.
    Rietveld, M. T.
    Bösinger, T.
    Thidé, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Leyser, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Brekke, A.
    Heater-induced phenomena in a coupled ionosphere-magnetosphere system2006In: Advances in Space Research, ISSN 0273-1177, Vol. 38, no 11, 2495-2502 p.Article in journal (Refereed)
    Abstract [en]

    Experimental results from HF pumping experiments in the nightside auroral E and F region are reported. The experiments were carried out by the use of the EISCAT HF heating facility located near Tromso, Norway, allowing HF pumping the ionosphere in a near magnetic field-aligned direction. We present experimental results from multi-instrument observations related to heater-induced phenomena in a coupled ionosphere-magnetosphere system. The following results have been observed on different occasions: a reverberation effect in scattered signals observed simultaneously on two diagnostic paths which is an indication of Alfven wave generation. This phenomenon was seen under specific disturbed background geophysical conditions, namely, a high electron density in the F region up to 8 MHz produced by soft electron precipitation from the magnetosphere along with low electron density in lower ionosphere; increased ionospheric electric fields; ion outflows from the ionosphere. On another occasion a magnetospheric response to heater turning on and off was found from magnetic pulsation observations over a frequency range up to 5 Hz (the upper frequency limit of the sensitive magnetometer at Kilpisjarvi, located near Tromso). The response manifests itself about 1 min after the heater is turned on and off. Other results have shown the modification of a natural auroral arc and local spiral-like formation. It is thought that a local heater-driven current system is formed. An interesting feature is the generation of the heater-induced ion outflows from the ionosphere. They are observed in night hours under both quiet and disturbed magnetic conditions.

  • 47.
    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.

  • 48. Blomberg, L. G.
    et al.
    Matsumoto, H.
    Bougeret, J. -L
    Kojima, H.
    Yagitani, S.
    Cumnock, J. A.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marklund, G. T.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Bylander, L.
    Åhlén, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Holtet, J. A.
    Ishisaka, K.
    Kallio, E.
    Kasaba, Y.
    Matsuoka, A.
    Moncuquet, M.
    Mursula, K.
    Omura, Y.
    Trotignon, J. G.
    MEFISTO - An electric field instrument for BepiColombo/MMO2006In: Advances in Space Research, ISSN 0273-1177, Vol. 38, no 4, 672-679 p.Article in journal (Refereed)
    Abstract [en]

    MEFISTO, together with the companion instrument WPT, are planning the first-ever in situ measurements of the electric field in the magnetosphere of planet Mercury. The instruments have been selected by JAXA for inclusion in the BepiColombo/MMO payload, as part of the Plasma Wave Investigation coordinated by Kyoto University. The magnetosphere of Mercury was discovered by Mariner 10 in 1974 and will be studied further by Messenger starting in 2011. However, neither spacecraft did or will measure the electric field. Electric fields are crucial in the dynamics of a magnetosphere and for the energy and plasma transport between different regions within the magnetosphere as well as between the magnetosphere and the surrounding regions. The MEFISTO instrument will be capable of measuring electric fields from DC to 3 MHz, and will thus also allow diagnostics of waves at all frequencies of relevance to the Hermean magnetosphere. MEFISTO is a double-probe electric field instrument. The double-probe technique has strong heritage and is well proven on missions such as Viking, Polar, and Cluster. For BepiColombo, a newly developed deployment mechanism is planned which reduces the mass by a factor of about 5 compared to conventional mechanisms for 15 in long booms. We describe the basic characteristics of the instrument and briefly discuss the new developments made to tailor the instrument to flight in Mercury orbit.

  • 49. Blomberg, L.G.
    et al.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Electric fields in the Hermean environment2006In: Advances in Space Research, ISSN 0273-1177, Vol. 38, no 4, 627-631 p.Article in journal (Refereed)
    Abstract [en]

    Returning to Mercury with the BepiColombo mission will provide a unique opportunity to obtain in situ information on the electric field in Mercury's magnetosphere. The electric field plays a crucial role for plasma transport in the magnetosphere, for transfer of energy between different parts of the system, and for propagation of information. Measuring the electric field, we will be able to better understand plasma motion and wave propagation in Mercury's magnetosphere. Together with knowledge of the magnetic field a better understanding will be derived of the magnetospheric current systems and their closure at or near the planetary surface. Further, insight into possible substorms at Mercury will be gained. We here focus on the expected amplitudes and frequencies of the electric fields concerned and the requirements for instrument capability that they pose.

  • 50. Bortnik, J.
    et al.
    Li, W.
    Thorne, R. M.
    Angelopoulos, V.
    Cully, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Bonnell, J.
    Le Contel, O.
    Roux, A.
    An Observation Linking the Origin of Plasmaspheric Hiss to Discrete Chorus Emissions2009In: Science, ISSN 0036-8075, Vol. 324, no 5928, 775-778 p.Article in journal (Refereed)
    Abstract [en]

    A long-standing problem in the field of space physics has been the origin of plasmaspheric hiss, a naturally occurring electromagnetic wave in the high-density plasmasphere (roughly within 20,000 kilometers of Earth) that is known to remove the high-energy Van Allen Belt electrons that pose a threat to satellites and astronauts. A recent theory tied the origin of plasmaspheric hiss to a seemingly different wave in the outer magnetosphere, but this theory was difficult to test because of a challenging set of observational requirements. Here we report on the experimental verification of the theory, made with a five-satellite NASA mission. This confirmation will allow modeling of plasmaspheric hiss and its effects on the high-energy radiation environment.

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