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  • 251.
    Emile, Olivier
    et al.
    Univ Rennes 1, F-35042 Rennes, France..
    Niemiec, Ronan
    Univ Rennes 1, F-35042 Rennes, France.;Univ Rennes 1, CNRS, UMR 6164, IETR, F-35042 Rennes, France..
    Brousseau, Christian
    Univ Rennes 1, CNRS, UMR 6164, IETR, F-35042 Rennes, France..
    Emile, Janine
    Univ Rennes 1, CNRS, UMR 6251, IPR, F-35042 Rennes, France..
    Mahdjoubi, Kouroch
    Univ Rennes 1, CNRS, UMR 6164, IETR, F-35042 Rennes, France..
    Wei, Wenlong
    Univ Rennes 1, CNRS, UMR 6164, IETR, F-35042 Rennes, France..
    Thidé, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mechanism of angular momentum transfer from microwaves to a copper ring2016In: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 70, no 8, article id 172Article in journal (Refereed)
    Abstract [en]

    In the exchange of orbital angular momentum between an electromagnetic wave and a copper ring we examine the origin of the Angular Momentum. We then investigate the transfer mechanism between the microwave and the object, and compare it with other mechanisms. We evidence a transfer mechanism based on the reflection of the electromagnetic field on the copper ring. In particular, at a microscopic scale, we show that the electromagnetic field induces alternative electric currents in the ring, with a small drift. Although little, the resistivity of copper leads to a force that rotates the ring. The estimation of the torque, which is of the order of 10(-8) Nm, is in good agreement with the experimental measurements. We also show that the transfer of electromagnetic orbital angular momentum to objects could be a way to measure the orbital angular momentum carried by electromagnetic fields, and we discuss possible applications.

  • 252.
    Engelhardt, Ilka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Plasma Structures at Enceladus’ South Polar Region2013Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The outflow of Saturns moon Enceladus is studied by analysing the electron density variation.Here the density variation of the 20 Hz data from the Cassini Radio Plasma Wave Science(RPWS) Langmuir Probe (LP) are presented. Of a total of 20 flybys 11 have been analysed onthe fine-structure of the electron densities.There is fine-structure to be found in the plume, but obvious association to the tiger stripes andsources of jets is not seen. Tiger stripes are a set of cracks in the ice sheet visible near thesouth pole of Enceladus. An increase in density near the tiger stripe region is also observed aswell as more fine structure close to the surface meaning that this might result from boundaryconditions like the cracks.The shape of the plume, due to plasma processes, its fine structure and jets needs to betaken into account as well as charging mechanisms of the dust, altitude dependencies and theelectromagnetic field.

  • 253.
    Engelhardt, Ilka. A. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Plasma and Dust at Saturn's Icy Moon Enceladus and Comet 67P/Churyumov-Gerasimenko2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Saturn’s moon Enceladus and comet 67P/Churyumov-Gerasimenko both are examples of icy solar system objects from which gas and dust flow into space. At both bodies, the gas becomes partly ionized and the dust grains get charged. Both bodies have been visited by spacecraft carrying similar Langmuir probe instruments for observing the plasma and the charged dust. The conditions at Enceladus and the comet turn out to be different, so we emphasize different aspects of their plasma environments. At Enceladus, we concentrate on the characteristic plasma regions and charged dust. At the comet, we investigate cold electrons.

    At Enceladus, internal frictional heating leads to gas escaping from cracks in the ice in the south pole region. This causes a plume of gas, which becomes partially ionized, and dust, becoming charged. We have investigated the plasma and charged nanodust in this region by the use of the Langmuir Probe (LP) of the Radio and Plasma Wave Science (RPWS) instrument on Cassini. The dust charge density can be calculated from the quasineutrality condition, the difference between ion and electron density measurements from LP. We found support for this method by comparing to measurements of larger dust grains by the RPWS electric antennas. We use the LP method to find that the plasma and dust environment of Enceladus can be divided into at least three regions. In addition to the well known plume, these are the plume edge and the trail region.

    At the comet, heat from the Sun sublimates ice to gas dragging dust along as it flows out into space. When gas molecules are hit by ionizing radiation we get a plasma. Models predict that the electron temperature just after ionization is around 10 eV, but that this collisions with the neutral gas should cool the electrons to below 0.1 eV. The Langmuir Probe instrument LAP has previously been used to show that the warm component exists at the comet. We present the first measurements of the cold component, co-existing with the warm component. We find that that the cold plasma often is observed as brief pulses in the LAP data, which we interpret as filamentation of the cold plasma.

    List of papers
    1. Plasma regions, charged dust and field-aligned currents near Enceladus
    Open this publication in new window or tab >>Plasma regions, charged dust and field-aligned currents near Enceladus
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    2015 (English)In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 117, p. 453-469Article in journal (Refereed) Published
    Abstract [en]

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

    Keywords
    Enceladus, Langmuir probe, Plasma, Charged dust, MAG, RPWS
    National Category
    Astronomy, Astrophysics and Cosmology
    Identifiers
    urn:nbn:se:uu:diva-268421 (URN)10.1016/j.pss.2015.09.010 (DOI)000364257400039 ()
    Funder
    Swedish National Space Board, 171/12Swedish National Space Board, 162/14
    Available from: 2015-12-04 Created: 2015-12-04 Last updated: 2018-04-18Bibliographically approved
    Download full text (pdf)
    fulltext
  • 254.
    Engelhardt, Ilka. A. D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Valliéres, X.
    Rubin, M.
    Gilet, N.
    Henri, P.
    Cold electrons at comet 67P/Churyumov-Gerasimenko2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 616, article id A51Article in journal (Refereed)
    Abstract [en]

    Context. The electron temperature of the plasma is one important aspect of the environment. Electrons created by photoionization or impact ionization of atmospheric gas have energies ∼10 eV. In an active comet coma the gas density is high enough for rapid cooling of the electron gas to the neutral gas temperature (few hundred kelvin). How cooling evolves in less active comets has not been studied before.

    Aims. To investigate how electron cooling varied as comet 67P/Churyumov-Gerasimenko changed its activity by three orders of magnitude during the Rosetta mission.

    Methods. We use in-situ data from Rosetta plasma and neutral gas sensors. By combining Langmuir probe bias voltage sweeps and Mutual Impedance Probe measurements we determine when cold electrons form at least 25% of the total electron density. We compare the results to what is expected from simple models of electron cooling, using the observed neutral gas density as input.

    Results. We demonstrate that the slope of the Langmuir probe sweep can be used as a proxy for cold electron presence. We show statistics of cold electron observations over the 2 year mission period. We find cold electrons at lower activity than expected by a simple model based on free radial expansion and continuous loss of electron energy. Cold electrons are seen mainly when the gas density indicates an exobase may have formed.

    Conclusions. Collisional cooling of electrons following a radial outward path is not sufficient for explaining the observations. We suggest the ambipolar electric field is important for the observed cooling. This field keeps electrons in the inner coma for much longer time, giving them time to dissipate energy by collisions with the neutrals. We conclude there is need of better models to describe the plasma environment of comets, including at least two populations of electrons and the ambipolar field.

  • 255.
    Engelhardt, Ilka. A. D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Stenberg Wieser, G.
    Goetz, C.
    Rubin, M.
    Henri, P.
    Nilsson, H.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Hajra, R.
    Valliéres, X.
    Plasma Density Structures at Comet 67P/Churyumov-Gerasimenko2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 477, no 1, p. 1296-1307Article in journal (Refereed)
    Abstract [en]

    We present Rosetta RPC case study from four events at various radial distance, phase angle and local time from autumn 2015, just after perihelion of comet 67P/Churyumov-Gerasimenko. Pulse like (high amplitude, up to minutes in time) signatures are seen with several RPC instruments in the plasma density (LAP, MIP), ion energy and flux (ICA) as well as magnetic field intensity (MAG). Furthermore the cometocentric distance relative to the electron exobase is seen to be a good organizing parameter for the measured plasma variations. The closer Rosetta is to this boundary, the more pulses are measured. This is consistent with the pulses being filaments of plasma originating from the diamagnetic cavity boundary as predicted by simulations. 

  • 256.
    Engelhardt, Ilka. A. D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Wahlund, Jan -Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders. I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ye, S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Kurth, W. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Morooka, M. W.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Farrell, W. M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Dougherty, M. K.
    Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London SW7 2BZ, England..
    Plasma regions, charged dust and field-aligned currents near Enceladus2015In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 117, p. 453-469Article in journal (Refereed)
    Abstract [en]

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

  • 257.
    Engelhardt, Ilka A.D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Plasma Structures at the Enceladus Plume2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cassini-RPWS high resolution (20 Hz) Langmuir probe data was analyzed to find the source of fast variations in the electron density especially in the Enceladus plume region. The spatial scale on the variations is between 1 and 10 km in size. The approaches were to check for correlations between the plasma density and its variations on one hand, and boundary conditions such as the cracks on Enceladus surface as well as dust and single jets on the other hand. None of these mechanisms could be identified as the only or dominating source of observed fine structure, though partial correlation can sometimes be found and the comparison to dust presence is qualitative more than quantitative. Along the way the charging mechanism in the plume was found to be most likely due to solar UV ionization since the maximum electron density was found to be around 200km altitude. Also the deformation of the plume in the corotation direction is visible in the 20 Hz data. 

    Download full text (pdf)
    EnceladusPlasma
  • 258.
    Engwall, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Double-Probe Measurements in Cold Tenuous Space Plasma Flows2006In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 34, no 5:2, p. 2071-2077Article in journal (Refereed)
    Abstract [en]

    Cold flowing tenuous plasmas are common in the terrestrial magnetosphere, particularly in the polar cap and tail lobe regions, which are filled by the supersonic plasma flow known as the polar wind. Electric field measurements with double-probe instruments in these regions suffer mainly from two error sources: 1) an apparent sunward electric field due to photoemission asymmetries in the probe-boom system and 2) an enhanced negatively charged wake forming behind the spacecraft, which will affect the probe measurements. The authors investigate these effects experimentally by Fourier analysis of the spin signature from the double-probe instrument Electric Fields and Waves (EFW) on the Cluster spacecraft. They show that while the signature due to photoemission asymmetry is very close to sinusoidal, the wake effect is characterized by a spectrum of spin harmonics. The Fourier decomposition can therefore be used for identifying wake effects in the data. As a spin-off, the analysis has also given information on the cold flowing ion population.

  • 259.
    Engwall, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
    Eriksson, Anders I.
    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.
    Dandouras, Iannis
    Centre d’Etude Spatiale des Rayonnements, Centre National de la Recherche Scientifique, Toulouse, Toulouse, France.
    Paschmann, Goetz
    International Space Science Institute, Bern, Switzerland..
    Quinn, Jack
    Center for Space Physics, Boston University, Boston, Massachusetts, USA..
    Torkar, Klaus
    Space Research Institute of the Austrian Academy of Science, Graz, Austria..
    Low-energy (order 10 eV) ion flow in the magnetotail lobes inferred from spacecraft wake observations2006In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 33, p. L06110-1-L06110-4Article in journal (Refereed)
    Abstract [en]

    Cold ionospheric ions with eV energies are common inthe magnetosphere and can travel far out in the magnetotail.However, they are difficult to measure with conventional ionspectrometers mounted on spacecraft, since the potential of asunlit spacecraft often reaches several tens of volts. In thispaper we present two alternative methods of measuring thecold-ion flow with the Cluster spacecraft and apply them onone case in the magnetotail at 18 RE: 1. Ion spectrometer incombination with artificial spacecraft potential control;2. Deriving ion flow velocity (both perpendicular andparallel) from electric field instruments. The secondmethod takes advantage of the effect on the doubleprobeinstrument of the wake formed behind a spacecraftin a plasma flow. The results from the two methods showgood agreement and are also consistent with polar windmodels and previous measurements at lower altitudes,confirming the continuation of low-energy ion outflows.

  • 260.
    Engwall, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cully, Christopher M.
    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.
    Puhl-Quinn, Pamela
    Space Science Center, University of New Hampshire, Durham, New Hampshire 03824-3525, USA.
    Vaith, Hans
    Space Science Center, University of New Hampshire, Durham, New Hampshire 03824-3525, USA.
    Torbert, Roy
    Space Science Center, University of New Hampshire, Durham, New Hampshire 03824-3525, USA.
    Survey of cold ionospheric outflows in the magnetotail2009In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, no 8, p. 3185-3201Article in journal (Refereed)
    Abstract [en]

    Low-energy ions escape from the ionosphere and constitute a large part of the magnetospheric content, especially in the geomagnetic tail lobes. However, they are normally invisible to spacecraft measurements, since the potential of a sunlit spacecraft in a tenuous plasma in many cases exceeds the energy-per-charge of the ions, and little is therefore known about their outflow properties far from the Earth. Here we present an extensive statistical study of cold ion outflows (0-60 eV) in the geomagnetic tail at geocentric distances from 5 to 19 R-E using the Cluster spacecraft during the period from 2001 to 2005. Our results were obtained by a new method, relying on the detection of a wake behind the spacecraft. We show that the cold ions dominate in both flux and density in large regions of the magnetosphere. Most of the cold ions are found to escape from the Earth, which improves previous estimates of the global outflow. The local outflow in the magnetotail corresponds to a global outflow of the order of 10(26) ions s(-1). The size of the outflow depends on different solar and magnetic activity levels.

  • 261.
    Engwall, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cully, Christopher M.
    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.
    Torbert, Roy
    Space Science Center, University of New Hampshire, Durham, New Hampshire 03824-3525, USA.
    Vaith, Hans
    Space Science Center, University of New Hampshire, Durham, New Hampshire 03824-3525, USA.
    Earth’s ionospheric outflow dominated by hidden cold plasma2009In: Nature Geoscience, ISSN 1752-0894, Vol. 2, no 1, p. 24-27Article in journal (Refereed)
    Abstract [en]

    The Earth constantly loses matter, mostly in the form of H+and O+ ions, through various outflow processes from the upper atmosphere and ionosphere. Most of these ions are cold (below 1 eV in thermal energy), but can still escape and travel farther out along the magnetic field lines into the magnetospheric tail lobes. The outflow has previously beenmeasured close to the Earth. To understand what fraction does not return but instead escapes, the measurements should be conducted at larger geocentric distances. However, at high altitudes the cold ions are normally invisible to spacecraft measurements, because the potential of a sunlit spacecraft exceeds the equivalent energy of the ions. Here we show that cold ions dominate in both flux and density in the distant magnetotail lobes, using a new measurement technique on the Cluster spacecraft. The total loss of cold hydrogen ions from the planet is inferred to be of the order of 1026 s−1, which is larger than the previously observed more energetic outflow. Quantification and insight of the loss processes of the Earth’s atmosphere and ionosphere are also important for understanding the evolution of atmospheres on other celestial bodies.

  • 262.
    Engwall, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics. 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.
    Forest, Julien
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wake formation behind positively charged spacecraft in flowing tenuous plasmas2006In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, no 6, article id 062904Article in journal (Refereed)
    Abstract [en]

    Spacecraft in tenuous plasmas become positively charged because of photoelectron emission. If the plasma is supersonically drifting with respect to the spacecraft, a wake forms behind it. When the kinetic energy of the positive ions in the plasma is not sufficient to overcome the electrostatic barrier of the spacecraft potential, they scatter on the potential structure from the spacecraft rather than get absorbed or scattered by the spacecraft body. For tenuous plasmas with Debye lengths much exceeding the spacecraft size, the potential structure extends far from the spacecraft, and consequently in this case the wake is of transverse dimensions much larger than the spacecraft. This enhanced wake formation process is demonstrated by theoretical analysis and computer simulations. Comparison to observations from the Cluster satellites shows good agreement.

  • 263.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Andersson, L. A.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Fowler, C. M.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Woodson, A. K.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Weber, T. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    McEnulty, T.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Morooka, M. W.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Stewart, A. I. F.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Mahaffy, P. R.
    NASA, Goddard Space Flight Ctr, Planetary Environm Lab, Code 699, Greenbelt, MD USA..
    Jakosky, B. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Enhanced O-2(+) loss at Mars due to an ambipolar electric field from electron heating2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 5, p. 4668-4678Article in journal (Refereed)
    Abstract [en]

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

  • 264. Ergun, R. E.
    et al.
    Andersson, L.
    Tao, J.
    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.
    Roux, A.
    LeContel, O.
    Glassmeier, K. -H
    Baumjohann, W.
    Observations of Double Layers in Earth's Plasma Sheet2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, no 15, p. 155002-Article in journal (Refereed)
    Abstract [en]

    We report the first direct observations of parallel electric fields (E-parallel to) carried by double layers (DLs) in the plasma sheet of Earth's magnetosphere. The DL observations, made by the THEMIS spacecraft, have E-parallel to signals that are analogous to those reported in the auroral region. DLs are observed during bursty bulk flow events, in the current sheet, and in plasma sheet boundary layer, all during periods of strong magnetic fluctuations. These observations imply that DLs are a universal process and that strongly nonlinear and kinetic behavior is intrinsic to Earth's plasma sheet.

  • 265.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Chen, L. -J
    Wilder, F. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Ahmadi, N.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Eriksson, S.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Usanova, M. E.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Goodrich, K. A.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Holmes, J. C.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Sturner, A. P.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Malaspina, D. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Newman, D. L.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.;Univ Colorado, Dept Phys, Boulder, CO 80309 USA..
    Torbert, R. B.
    Univ New Hampshire, Durham, NH 03824 USA.;Southwest Res Inst, San Antonio, TX USA..
    Argall, M. R.
    Univ New Hampshire, Durham, NH 03824 USA..
    Lindqvist, P. -A
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Webster, J. M.
    Southwest Res Inst, San Antonio, TX USA..
    Drake, J. F.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Price, L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Cassak, P. A.
    West Virginia Univ, Morgantown, WV USA..
    Swisdak, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Shay, M. A.
    Univ Delaware, Newark, DE USA..
    Graham, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Strangeway, R. J.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gershman, D.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.;Univ Maryland, IREAP, College Pk, MD 20742 USA..
    Avanov, L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Hesse, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, Toulouse, France.;Ctr Natl Rech Sci, Toulouse, France..
    Le Contel, O.
    Lab Phys Plasmas, Palaiseau, France..
    Retino, A.
    Lab Phys Plasmas, Palaiseau, France..
    Phan, T. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Goldman, M. V.
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA..
    Stawarz, J. E.
    Imperial Coll London, Blackett Lab, London, England..
    Schwartz, S. J.
    Imperial Coll London, Blackett Lab, London, England..
    Eastwood, J. P.
    Imperial Coll London, Blackett Lab, London, England..
    Hwang, K. -J
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Wang, S.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.;Univ Maryland, IREAP, College Pk, MD 20742 USA..
    Drift waves, intense parallel electric fields, and turbulence associated with asymmetric magnetic reconnection at the magnetopause2017In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, no 7, p. 2978-2986Article in journal (Refereed)
    Abstract [en]

    Observations of magnetic reconnection at Earth's magnetopause often display asymmetric structures that are accompanied by strong magnetic field (B) fluctuations and large-amplitude parallel electric fields (E-||). The B turbulence is most intense at frequencies above the ion cyclotron frequency and below the lower hybrid frequency. The B fluctuations are consistent with a thin, oscillating current sheet that is corrugated along the electron flow direction (along the X line), which is a type of electromagnetic drift wave. Near the X line, electron flow is primarily due to a Hall electric field, which diverts ion flow in asymmetric reconnection and accompanies the instability. Importantly, the drift waves appear to drive strong parallel currents which, in turn, generate large-amplitude (similar to 100mV/m) E-|| in the form of nonlinear waves and structures. These observations suggest that turbulence may be common in asymmetric reconnection, penetrate into the electron diffusion region, and possibly influence the magnetic reconnection process.

  • 266.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Goodrich, K. A.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Wilder, F. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Ahmadi, N.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Holmes, J. C.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Eriksson, S.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Stawarz, J. E.
    Imperial Coll London, Blackett Lab, London, England.
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Genestreti, K. J.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Hesse, M.
    Univ Bergen, Dept Phys & Technol, Bergen, Norway.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA.
    Torbert, R. B.
    Southwest Res Inst, San Antonio, TX USA;Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA.
    Phan, T. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.
    Schwartz, S. J.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Eastwood, J. P.
    Imperial Coll London, Blackett Lab, London, England.
    Strangeway, R. J.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA.
    Le Contel, O.
    Univ Paris Sud, Observ Paris, Sorbonne Univ, Lab Phys Plasmas,CNRS,Ecole Polytech, Paris, France.
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA.
    Argall, M. R.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA.
    Lindqvist, P. -A
    Chen, L. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA;Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
    Cassak, P. A.
    West Univ Virginia, Dept Phys & Astron, Morgantown, WV USA.
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Gershman, D.
    West Univ Virginia, Dept Phys & Astron, Morgantown, WV USA.
    Leonard, T. W.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, Toulouse, France;CNRS, Toulouse, France.
    Retino, A.
    Univ Paris Sud, Observ Paris, Sorbonne Univ, Lab Phys Plasmas,CNRS,Ecole Polytech, Paris, France.
    Matthaeus, W.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Magnetic Reconnection, Turbulence, and Particle Acceleration: Observations in the Earth's Magnetotail2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 8, p. 3338-3347Article in journal (Refereed)
    Abstract [en]

    We report observations of turbulent dissipation and particle acceleration from large-amplitude electric fields (E) associated with strong magnetic field (B) fluctuations in the Earth's plasma sheet. The turbulence occurs in a region of depleted density with anti-earthward flows followed by earthward flows suggesting ongoing magnetic reconnection. In the turbulent region, ions and electrons have a significant increase in energy, occasionally > 100 keV, and strong variation. There are numerous occurrences of vertical bar E vertical bar > 100 mV/m including occurrences of large potentials (> 1 kV) parallel to B and occurrences with extraordinarily large J.E (J is current density). In this event, we find that the perpendicular contribution of J.E with frequencies near or below the ion cyclotron frequency (f(ci)) provide the majority net positive J.E. Large-amplitude parallel E events with frequencies above f(ci) to several times the lower hybrid frequency provide significant dissipation and can result in energetic electron acceleration. Plain Language Summary The Magnetospheric Multiscale mission is able to examine dissipation associated with magnetic reconnection with unprecedented accuracy and frequency response. The observations show that roughly 80% of the dissipation is from the perpendicular currents and electric fields. However, large-amplitude parallel electric fields appear to play a strong role in turbulent dissipation into electrons and in electron acceleration.

  • 267.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80303 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80303 USA..
    Goodrich, K. A.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80303 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80303 USA..
    Wilder, F. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80303 USA..
    Holmes, J. C.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80303 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80303 USA..
    Stawarz, J. E.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80303 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80303 USA..
    Eriksson, S.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80303 USA..
    Sturner, A. P.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80303 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80303 USA..
    Malaspina, D. M.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80303 USA..
    Usanova, M. E.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80303 USA..
    Torbert, R. B.
    Univ New Hampshire, Durham, NH 03824 USA.;Southwest Res Inst, San Antonio, TX 78238 USA..
    Lindqvist, P. -A
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Los Angeles, CA 90095 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA 90095 USA..
    Pollock, C. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Hesse, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Chen, L. J.
    Univ Maryland, College Pk, MD 20742 USA..
    Lapenta, G.
    Leuven Univ, Leuven, Belgium..
    Goldman, M. V.
    Univ Colorado, Dept Phys, Boulder, CO 80303 USA..
    Newman, D. L.
    Univ Colorado, Dept Phys, Boulder, CO 80303 USA..
    Schwartz, S. J.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80303 USA.;Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London, England..
    Eastwood, J. P.
    Univ London Imperial Coll Sci Technol & Med, Blackett Lab, London, England..
    Phan, T. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Mozer, F. S.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Drake, J.
    Univ Maryland, College Pk, MD 20742 USA..
    Shay, M. A.
    Univ Delaware, Newark, DE 19716 USA..
    Cassak, P. A.
    W Virginia Univ, Morgantown, WV 26506 USA..
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, A-8010 Graz, Austria..
    Marklund, G.
    KTH Royal Inst Technol, Stockholm, Sweden..
    Magnetospheric Multiscale Satellites Observations of Parallel Electric Fields Associated with Magnetic Reconnection2016In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 116, no 23, article id 235102Article in journal (Refereed)
    Abstract [en]

    We report observations from the Magnetospheric Multiscale satellites of parallel electric fields (E-vertical bar vertical bar) associated with magnetic reconnection in the subsolar region of the Earth's magnetopause. E-vertical bar vertical bar events near the electron diffusion region have amplitudes on the order of 100 mV/m, which are significantly larger than those predicted for an antiparallel reconnection electric field. This Letter addresses specific types of E-vertical bar vertical bar events, which appear as large-amplitude, near unipolar spikes that are associated with tangled, reconnected magnetic fields. These E-vertical bar vertical bar events are primarily in or near a current layer near the separatrix and are interpreted to be double layers that may be responsible for secondary reconnection in tangled magnetic fields or flux ropes. These results are telling of the three-dimensional nature of magnetopause reconnection and indicate that magnetopause reconnection may be often patchy and/or drive turbulence along the separatrix that results in flux ropes and/or tangled magnetic fields.

  • 268.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Hoilijoki, S.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Ahmadi, N.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Schwartz, S. J.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Wilder, F. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA.
    Torbert, R. B.
    Southwest Res Inst, San Antonio, TX USA;Univ New Hampshire, Dept Phys, Durham, NH 03824 USA.
    Lindqvist, P-A
    Royal Inst Technol, Stockholm, Sweden.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Strangeway, R. J.
    Univ Calif Los Angeles, IGGP, Los Angeles, CA USA.
    Le Contel, O.
    Lab Phys Plasmas, Palaiseau, France.
    Holmes, J. C.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Stawarz, J. E.
    Imperial Coll London, Blackett Lab, London, England.
    Goodrich, K. A.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.
    Eriksson, S.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Gershman, D.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Chen, L. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA;Univ Maryland, IREAP, College Pk, MD 20742 USA.
    Magnetic Reconnection in Three Dimensions: Observations of Electromagnetic Drift Waves in the Adjacent Current Sheet2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 12, p. 10104-10118Article in journal (Refereed)
    Abstract [en]

    Magnetic reconnection at the subsolar magnetopause is persistently accompanied by strong fluctuations of the magnetic field (B), plasma density (n), and all components of the electric field (E) and current (J). The strongest fluctuations are at frequencies below the lower hybrid frequency and observed in a thin, intense current sheet adjacent to the electron diffusion region. In this current sheet, the background magnitudes of B and n are changing considerably, creating an inhomogeneous plasma environment. We show that the fluctuations in B and n are consistent with an oscillatory displacement of the current sheet in the surface normal direction. The displacement is propagating parallel to the magnetic reconnection X line. Wavelengths are on the order of or longer than the thickness of the current sheet to which they are confined, so we label these waves electromagnetic drift waves. E and J fluctuations are more complex than a simple displacement. They have significant variations in the component along B, which suggest that the drift waves also may be confined along B. The current sheet is supported by an electron drift driven by normal electric field, which, in turn, is balanced by an ion pressure gradient. We suggest that wave growth comes from an instability related to the drift between the electrons and ions. We discuss the possibility that drift waves can displace or penetrate into the electron diffusion region giving magnetic reconnection three-dimensional structure. Drift waves may corrugate the X line, possibly breaking the X line and generating turbulence.

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  • 269.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Hoilijoki, S.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Ahmadi, N.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Schwartz, S. J.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Wilder, F. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Drake, J. F.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
    Hesse, M.
    Univ Bergen, Birkeland Ctr Space Sci, Bergen, Norway.
    Shay, M. A.
    Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA.
    Ji, H.
    Princeton Plasma Phys Lab, POB 451, Princeton, NJ 08543 USA;Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA.
    Yamada, M.
    Princeton Plasma Phys Lab, POB 451, Princeton, NJ 08543 USA.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cassak, P. A.
    West Virginia Univ, Dept Phys & Astron, Morgantown, WV 26506 USA.
    Swisdak, M.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA.
    Torbert, R. B.
    Southwest Res Inst, San Antonio, TX USA;Univ New Hampshire, Dept Phys, Durham, NH 03824 USA.
    Holmes, J. C.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Stawarz, J. E.
    Imperial Coll London, Blackett Lab, London, England.
    Goodrich, K. A.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.
    Eriksson, S.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.
    Strangeway, R. J.
    Univ Calif Los Angeles, IGGP, Los Angeles, CA USA.
    LeContel, O.
    Lab Phys Plasmas, Palaiseau, France.
    Magnetic Reconnection in Three Dimensions: Modeling and Analysis of Electromagnetic Drift Waves in the Adjacent Current Sheet2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 12, p. 10085-10103Article in journal (Refereed)
    Abstract [en]

    We present a model of electromagnetic drift waves in the current sheet adjacent to magnetic reconnection at the subsolar magnetopause. These drift waves are potentially important in governing 3-D structure of subsolar magnetic reconnection and in generating turbulence. The drift waves propagate nearly parallel to the X line and are confined to a thin current sheet. The scale size normal to the current sheet is significantly less than the ion gyroradius and can be less than or on the order of the wavelength. The waves also have a limited extent along the magnetic field (B), making them a three-dimensional eigenmode structure. In the current sheet, the background magnitudes of B and plasma density change significantly, calling for a treatment that incorporates an inhomogeneous plasma environment. Using detailed examination of Magnetospheric Multiscale observations, we find that the waves are best represented by series of electron vortices, superimposed on a primary electron drift, that propagate along the current sheet (parallel to the X line). The waves displace or corrugate the current sheet, which also potentially displaces the electron diffusion region. The model is based on fluid behavior of electrons, but ion motion must be treated kinetically. The strong electron drift along the X line is likely responsible for wave growth, similar to a lower hybrid drift instability. Contrary to a classical lower hybrid drift instability, however, the strong changes in the background B and n(o), the normal confinement to the current sheet, and the confinement along B are critical to the wave description.

  • 270.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Holmes, J. C.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Goodrich, K. A.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Wilder, F. D.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Stawarz, J. E.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Eriksson, S.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Newman, D. L.
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA..
    Schwartz, S. J.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA.;Imperial Coll London, Blackett Lab, London, England..
    Goldman, M. V.
    Univ Colorado, Dept Phys, Boulder, CO 80309 USA..
    Sturner, A. P.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Malaspina, D. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Usanova, M. E.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Torbert, R. B.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA.;Southwest Res Inst, San Antonio, TX USA..
    Argall, M.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Lindqvist, P-A
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA..
    Pollock, C. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Avanov, L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Hesse, M.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Chen, L. J.
    Univ Maryland, Dept Phys, College Pk, MD 20742 USA..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, Toulouse, France.;CNRS, Toulouse, France..
    Le Contel, O.
    Lab Phys Plasmas, Palaiseau, France..
    Retino, A.
    Lab Phys Plasmas, Palaiseau, France..
    Phan, T. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Eastwood, J. P.
    Imperial Coll London, Blackett Lab, London, England..
    Oieroset, M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Drake, J.
    Univ Maryland, Dept Phys, College Pk, MD 20742 USA..
    Shay, M. A.
    Univ Delaware, Dept Phys & Astron, Bartol Res Inst, Newark, DE 19716 USA..
    Cassak, P. A.
    West Virginia Univ, Dept Phys & Astron, Morgantown, WV USA..
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Zhou, M.
    Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA USA..
    Ashour-Abdalla, M.
    Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA USA..
    Andre, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Magnetospheric Multiscale observations of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the magnetopause2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 11, p. 5626-5634Article in journal (Refereed)
    Abstract [en]

    We report observations from the Magnetospheric Multiscale satellites of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the Earth's magnetopause. The observed waves have parallel electric fields (E-||) with amplitudes on the order of 100mV/m and display nonlinear characteristics that suggest a possible net E-||. These waves are observed within the ion diffusion region and adjacent to (within several electron skin depths) the electron diffusion region. They are in or near the magnetosphere side current layer. Simulation results support that the strong electrostatic linear and nonlinear wave activities appear to be driven by a two stream instability, which is a consequence of mixing cold (<10eV) plasma in the magnetosphere with warm (similar to 100eV) plasma from the magnetosheath on a freshly reconnected magnetic field line. The frequent observation of these waves suggests that cold plasma is often present near the magnetopause.

  • 271.
    Ergun, R. E.
    et al.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Morooka, M. W.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Andersson, L. A.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Fowler, C. M.
    Univ Colorado, Dept Astrophys & Planetary Sci, Boulder, CO 80309 USA.;Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Delory, G. T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Eriksson, Anders I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    McEnulty, T.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Jakosky, B. M.
    Univ Colorado, Lab Atmospher & Space Sci, Boulder, CO 80309 USA..
    Dayside electron temperature and density profiles at Mars: First results from the MAVEN Langmuir probe and waves instrument2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, no 21, p. 8846-8853Article in journal (Refereed)
    Abstract [en]

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

  • 272.
    Eriksson, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Boström, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gill, Reine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Åhlén, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Jansson, Sven-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mälkki, A.
    Holtet, J. A.
    Lybekk, B.
    Pedersen, A.
    Blomberg, L. G.
    RPC-LAP: The Rosetta Langmuir probe instrument2007In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 128, no 1-4, p. 729-744Article, review/survey (Refereed)
    Abstract [en]

    The Rosetta dual Langmuir probe instrument, LAP, utilizes the multiple powers of a pair of spherical Langmuir probes for measurements of basic plasma parameters with the aim of providing detailed knowledge of the outgassing, ionization, and subsequent plasma processes around the Rosetta target comet. The fundamental plasma properties to be studied are the plasma density, the electron temperature, and the plasma flow velocity. However, study of electric fields up to 8 kHz, plasma density fluctuations, spacecraft potential, integrated UV flux, and dust impacts is also possible. LAP is fully integrated in the Rosetta Plasma Consortium (RPC), the instruments of which together provide a comprehensive characterization of the cometary plasma.

  • 273.
    Eriksson, Anders I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Engelhardt, Ilka. A. D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Boström, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johansson, Fredrik L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Odelstad, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Henri, P.
    LPC2E, Lab Phys & Chim Environm & Espace.
    Lebreton, J. -P
    LPC2E, Lab Phys & Chim Environm & Espace.
    Miloch, W. J.
    Univ Oslo, Dept Phys.
    Paulsson, J. J. P.
    Univ Oslo, Dept Phys.
    Wedlund, Cyril Simon
    Univ Oslo, Dept Phys.
    Yang, L.
    Univ Oslo, Dept Phys.
    Karlsson, T.
    Royal Inst Technol, Alfvén Lab.
    Jarvinen, R.
    Finnish Meteorol Inst, Helsinki 00560.
    Broiles, Thomas
    Southwest Res Inst, San Antonio.
    Mandt, K.
    Southwest Res Inst, San Antonio; Univ Texas San Antonio, Dept Phys & Astron.
    Carr, C. M.
    Imperial Coll London, Dept Phys.
    Galand, M.
    Imperial Coll London, Dept Phys.
    Nilsson, H.
    Swedish Inst Space Phys, S-98128 Kiruna.
    Norberg, C.
    Swedish Inst Space Phys, S-98128 Kiruna.
    Cold and warm electrons at comet 67P/Churyumov-Gerasimenko2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 605, article id A15Article in journal (Refereed)
    Abstract [en]

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

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

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

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

  • 274.
    Eriksson, Elin
    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.
    3D Magnetic Nulls and Regions of Strong Current in the Earth's Magnetosphere2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Plasma, a gas of charged particles exhibiting collective behaviour, can be found everywhere in our vast Universe. The characteristics of plasma in very distant parts of the Universe can be similar to characteristics in our solar system and near-Earth space. We can therefore gain an understanding of what happens in astrophysical plasmas by studying processes occurring in near Earth space, an environment much easier to reach.

    Large volumes in space are filled with plasma and when different plasmas interact distinct boundaries are often created. Many important physical processes, for example particle acceleration, occur at these boundaries. Thus, it is very important to study and understand such boundaries. In Paper I we study magnetic nulls, regions of vanishing magnetic fields, that form inside boundaries separating plasmas with different magnetic field orientations. For the first time, a statistical study of magnetic nulls in the Earth’s nightside magnetosphere has been done by using simultaneous measurements from all four Cluster spacecraft. We find that magnetic nulls occur both in the magnetopause and the magnetotail. In addition, we introduce a method to determine the reliability of the type identification of the observed nulls. In the manuscript of Paper II we study a different boundary, the shocked solar wind plasma in the magnetosheath, using the new Magnetospheric Multiscale mission. We show that a region of strong current in the form of a current sheet is forming inside the turbulent magnetosheath behind a quasi-parallel shock. The strong current sheet can be related to the jets with extreme dynamic pressure, several times that of the undisturbed solar wind dynamic pressure. The current sheet is also associated with electron acceleration parallel to the background magnetic field. In addition, the current sheet satisfies the Walén relation suggesting that plasmas on both sides of the current region are magnetically connected. We speculate on the formation mechanisms of the current sheet and the physical processes inside and around the current sheet.

    List of papers
    1. Statistics and accuracy of magnetic null identification in multispacecraft data
    Open this publication in new window or tab >>Statistics and accuracy of magnetic null identification in multispacecraft data
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    2015 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, p. 6883-6889Article in journal (Refereed) Published
    Abstract [en]

    Complex magnetic topologies are ubiquitous in astrophysical plasmas. Analyzing magnetic nulls, regions of vanishing magnetic field, is one way to characterize 3-D magnetic topologies. Magnetic nulls are believed to be important in 3-D reconnection and turbulence. In the vicinity of a null, plasma particles become unmagnetized and can be accelerated to high energies by electric fields. We present the first statistical study of the occurrence of magnetic nulls and their types in the Earth's nightside magnetosphere. We are able to identify the nulls both in the tail and in the magnetopause current sheets. On average, we find one null for every few current sheet crossings. We show that the type identification of magnetic nulls may be sensitive to local fluctuations in the magnetic field. We develop and demonstrate a method to estimate the reliability of the magnetic null type identification.

    National Category
    Geophysics Fusion, Plasma and Space Physics
    Identifiers
    urn:nbn:se:uu:diva-267334 (URN)10.1002/2015GL064959 (DOI)000363411200002 ()
    Funder
    Swedish Research Council, 2013-4309
    Available from: 2015-11-24 Created: 2015-11-20 Last updated: 2018-09-06Bibliographically approved
    2. Kinetic Study of Thin Current Sheet in Magnetosheath Jet
    Open this publication in new window or tab >>Kinetic Study of Thin Current Sheet in Magnetosheath Jet
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    (English)Manuscript (preprint) (Other academic)
    Keywords
    Current sheet, Particle acceleration, Magnetosheath
    National Category
    Fusion, Plasma and Space Physics
    Research subject
    Physics with specialization in Space and Plasma Physics
    Identifiers
    urn:nbn:se:uu:diva-292738 (URN)
    Funder
    Swedish Research Council, 2013-4309
    Available from: 2016-05-09 Created: 2016-05-09 Last updated: 2018-06-20
    Download full text (pdf)
    EE_Lic
  • 275.
    Eriksson, Elin
    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.
    Electron energization in near-Earth space: Studies of kinetic scales using multi-spacecraft data2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Plasma, a gas of charged particles exhibiting collective behavior, is everywhere in the Universe. The heating of plasma to millions of degrees and acceleration of charged particles to very high energies has been observed in many astrophysical environments. How and where the heating and acceleration occur is in many cases unclear. In most astrophysical environments, plasma consists of negative electrons and positive ions. In this thesis we focus on understanding the heating and acceleration of electrons. Several plasma processes have been proposed to explain the observed acceleration. However, the exact heating and acceleration mechanisms involved and their importance are still unclear. This thesis contributes toward a better understanding of this topic by using observations from two multi-spacecraft missions, Cluster and the Magnetospheric MultiScale (MMS), in near-Earth space.

    In Article I we look at magnetic nulls, regions of vanishing magnetic field B believed to be important in particle acceleration, in the Earth's nightside magnetosphere. We find that nulls are common at the nightside magnetosphere and that the characterization of the B geometry around a null can be affected by localized B fluctuations. We develop and present a method for determining the effect of the B fluctuation on the null's characterization.

    In Article II we look at a thin (a few km) current sheet (CS) in the turbulent magnetosheath. Observations suggest local electron heating and beam formation parallel to B inside the CS. The electron observations fits well with the theory of electron acceleration across a shock due to a potential difference. However, in our case the electron beams are formed locally inside the magnetosheath that is contrary to current belief that the beam formation only occurs at the shock.

    In Article III we present observations of electron energization inside a very thin (thinner than Article II) reconnecting CS located in the turbulent magnetosheath. Currently, very little is know about electron acceleration mechanisms at these small scales. MMS observe local electron heating and acceleration parallel to B when crossing the CS. We show that the energized electrons correspond to acceleration due to a quasi-static potential difference rather than electrostatic waves. This energization is similar to what has been observed inside ion diffusion regions at the magnetopause and magnetotail. Thus, despite the different plasma conditions a similar energization occurs in all these plasma regions.

    In Article IV we study electron acceleration by Fermi acceleration, betatron acceleration, and acceleration due to parallel electric fields inside tailward plasma jets formed due to reconnection, the so called tailward outflow region. We show that most observations are consistent with local electron heating and acceleration from a simplified two dimensional picture of Fermi acceleration and betatron acceleration in an outflow region. We find that Fermi acceleration is the dominant electron acceleration mechanism.

    List of papers
    1. Statistics and accuracy of magnetic null identification in multispacecraft data
    Open this publication in new window or tab >>Statistics and accuracy of magnetic null identification in multispacecraft data
    Show others...
    2015 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, p. 6883-6889Article in journal (Refereed) Published
    Abstract [en]

    Complex magnetic topologies are ubiquitous in astrophysical plasmas. Analyzing magnetic nulls, regions of vanishing magnetic field, is one way to characterize 3-D magnetic topologies. Magnetic nulls are believed to be important in 3-D reconnection and turbulence. In the vicinity of a null, plasma particles become unmagnetized and can be accelerated to high energies by electric fields. We present the first statistical study of the occurrence of magnetic nulls and their types in the Earth's nightside magnetosphere. We are able to identify the nulls both in the tail and in the magnetopause current sheets. On average, we find one null for every few current sheet crossings. We show that the type identification of magnetic nulls may be sensitive to local fluctuations in the magnetic field. We develop and demonstrate a method to estimate the reliability of the magnetic null type identification.

    National Category
    Geophysics Fusion, Plasma and Space Physics
    Identifiers
    urn:nbn:se:uu:diva-267334 (URN)10.1002/2015GL064959 (DOI)000363411200002 ()
    Funder
    Swedish Research Council, 2013-4309
    Available from: 2015-11-24 Created: 2015-11-20 Last updated: 2018-09-06Bibliographically approved
    2. Strong current sheet at a magnetosheath jet: Kinetic structure and electron acceleration
    Open this publication in new window or tab >>Strong current sheet at a magnetosheath jet: Kinetic structure and electron acceleration
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    2016 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 10, p. 9608-9618Article in journal (Refereed) Published
    Abstract [en]

    Localized kinetic-scale regions of strong current are believed to play an important role in plasma thermalization and particle acceleration in turbulent plasmas. We present a detailed study of a strong localized current, 4900 nA m(-2), located at a fast plasma jet observed in the magnetosheath downstream of a quasi-parallel shock. The thickness of the current region is similar to 3 ion inertial lengths and forms at a boundary separating magnetosheath-like and solar wind-like plasmas. On ion scales the current region has the shape of a sheet with a significant average normal magnetic field component but shows strong variations on smaller scales. The dynamic pressure within the magnetosheath jet is over 3 times the solar wind dynamic pressure. We suggest that the current sheet is forming due to high velocity shears associated with the jet. Inside the current sheet we observe local electron acceleration, producing electron beams, along the magnetic field. However, there is no clear sign of ongoing reconnection. At higher energies, above the beam energy, we observe a loss cone consistent with part of the hot magnetosheath-like electrons escaping into the colder solar wind-like plasma. This suggests that the acceleration process within the current sheet is similar to the one that occurs at shocks, where electron beams and loss cones are also observed. Therefore, electron beams observed in the magnetosheath do not have to originate from the bow shock but can also be generated locally inside the magnetosheath.

    National Category
    Fusion, Plasma and Space Physics
    Identifiers
    urn:nbn:se:uu:diva-312116 (URN)10.1002/2016JA023146 (DOI)000388965900020 ()
    Available from: 2017-01-09 Created: 2017-01-04 Last updated: 2019-11-22Bibliographically approved
    3. Electron Energization at a Reconnecting Magnetosheath Current Sheet
    Open this publication in new window or tab >>Electron Energization at a Reconnecting Magnetosheath Current Sheet
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    2018 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 16Article in journal, Letter (Refereed) Published
    Abstract [en]

    We present observations of electron energization within a sub-ion-scale magnetosheath current sheet (CS). A number of signatures indicate ongoing reconnection, including the thickness of the CS (∼0.7 ion inertial length), nonzero normal magnetic field, Hall magnetic fields with electrons carrying the Hall currents, and electron heating. We observe localized electron acceleration and heating parallel to the magnetic field at the edges of the CS. Electrostatic waves observed in these regions have low phase velocity and small wave potentials and thus cannot provide the observed acceleration and heating. Instead, we find that the electrons are accelerated by a parallel potential within the separatrix regions. Similar acceleration has been reported based on magnetopause and magnetotail observations.Thus, despite the different plasma conditions in magnetosheath, magnetopause, and magnetotail,the acceleration mechanism and corresponding heating of electrons is similar.

    Keywords
    magnetic reconnection, magnetosheath, electron heating, electron acceleration, Magnetospheric Multiscale
    National Category
    Other Physics Topics
    Research subject
    Physics with specialization in Space and Plasma Physics
    Identifiers
    urn:nbn:se:uu:diva-359592 (URN)10.1029/2018GL078660 (DOI)000445612500023 ()
    Funder
    Swedish Research Council, 2013-4309Swedish National Infrastructure for Computing (SNIC), m.2017-1-422Swedish National Infrastructure for Computing (SNIC), m.2016-457
    Available from: 2018-09-04 Created: 2018-09-04 Last updated: 2018-10-25Bibliographically approved
    4. Electron acceleration in a magnetotail reconnection outflow region using Magnetospheric MultiScale data
    Open this publication in new window or tab >>Electron acceleration in a magnetotail reconnection outflow region using Magnetospheric MultiScale data
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    2020 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 47, no 1, article id e2019GL085080Article in journal (Refereed) Published
    National Category
    Fusion, Plasma and Space Physics
    Research subject
    Physics with specialization in Space and Plasma Physics
    Identifiers
    urn:nbn:se:uu:diva-359593 (URN)10.1029/2019GL085080 (DOI)000513983400005 ()
    Funder
    Swedish Research Council, 2013-4309
    Available from: 2018-09-06 Created: 2018-09-06 Last updated: 2020-03-23Bibliographically approved
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  • 276.
    Eriksson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Space & Plasma Phys, Stockholm, Sweden.
    Alm, Love
    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.
    Khotyaintsev, Yuri V.
    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.
    Electron acceleration in a magnetotail reconnection outflow region using Magnetospheric MultiScale data2020In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 47, no 1, article id e2019GL085080Article in journal (Refereed)
    Download full text (pdf)
    fulltext
  • 277.
    Eriksson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    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.
    Divin, Andrey
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Physics Department, St. Petersburg State University, St. Petersburg, Russia.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Yordanova, Emiliya
    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. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Electron Energization at a Reconnecting Magnetosheath Current Sheet2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 16Article in journal (Refereed)
    Abstract [en]

    We present observations of electron energization within a sub-ion-scale magnetosheath current sheet (CS). A number of signatures indicate ongoing reconnection, including the thickness of the CS (∼0.7 ion inertial length), nonzero normal magnetic field, Hall magnetic fields with electrons carrying the Hall currents, and electron heating. We observe localized electron acceleration and heating parallel to the magnetic field at the edges of the CS. Electrostatic waves observed in these regions have low phase velocity and small wave potentials and thus cannot provide the observed acceleration and heating. Instead, we find that the electrons are accelerated by a parallel potential within the separatrix regions. Similar acceleration has been reported based on magnetopause and magnetotail observations.Thus, despite the different plasma conditions in magnetosheath, magnetopause, and magnetotail,the acceleration mechanism and corresponding heating of electrons is similar.

  • 278.
    Eriksson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    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.
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Hietala, H.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA USA..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    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..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Lavraud, B.
    CNRS, IRAP, Toulouse, France..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Pollock, C. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Saito, Y.
    JAXA, Chofu, Tokyo, Japan..
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Russell, C.
    Torbert, R.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Ergun, R.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA..
    Lindqvist, P-A
    Burch, J.
    Southwest Res Inst, San Antonio, TX USA..
    Strong current sheet at a magnetosheath jet: Kinetic structure and electron acceleration2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 10, p. 9608-9618Article in journal (Refereed)
    Abstract [en]

    Localized kinetic-scale regions of strong current are believed to play an important role in plasma thermalization and particle acceleration in turbulent plasmas. We present a detailed study of a strong localized current, 4900 nA m(-2), located at a fast plasma jet observed in the magnetosheath downstream of a quasi-parallel shock. The thickness of the current region is similar to 3 ion inertial lengths and forms at a boundary separating magnetosheath-like and solar wind-like plasmas. On ion scales the current region has the shape of a sheet with a significant average normal magnetic field component but shows strong variations on smaller scales. The dynamic pressure within the magnetosheath jet is over 3 times the solar wind dynamic pressure. We suggest that the current sheet is forming due to high velocity shears associated with the jet. Inside the current sheet we observe local electron acceleration, producing electron beams, along the magnetic field. However, there is no clear sign of ongoing reconnection. At higher energies, above the beam energy, we observe a loss cone consistent with part of the hot magnetosheath-like electrons escaping into the colder solar wind-like plasma. This suggests that the acceleration process within the current sheet is similar to the one that occurs at shocks, where electron beams and loss cones are also observed. Therefore, electron beams observed in the magnetosheath do not have to originate from the bow shock but can also be generated locally inside the magnetosheath.

    Download full text (pdf)
    fulltext
  • 279.
    Eriksson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Graham, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Yordanova, Emiliya
    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.
    Russell, Christopher
    Torbert, Roy
    Giles, Barbara
    Pollock, Craig
    Lindqvist, Per-Arne
    Ergun, Robert
    Magnes, Werner
    Burch, James
    Kinetic Study of Thin Current Sheet in Magnetosheath JetManuscript (preprint) (Other academic)
  • 280.
    Eriksson, Elin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyaintsev, Yuri. V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Khotyayintsev, V. M.
    Taras Shevchenko Natl Univ Kyiv, Dept Theoret Phys, Kiev, Ukraine..
    Andre, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Statistics and accuracy of magnetic null identification in multispacecraft data2015In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 42, p. 6883-6889Article in journal (Refereed)
    Abstract [en]

    Complex magnetic topologies are ubiquitous in astrophysical plasmas. Analyzing magnetic nulls, regions of vanishing magnetic field, is one way to characterize 3-D magnetic topologies. Magnetic nulls are believed to be important in 3-D reconnection and turbulence. In the vicinity of a null, plasma particles become unmagnetized and can be accelerated to high energies by electric fields. We present the first statistical study of the occurrence of magnetic nulls and their types in the Earth's nightside magnetosphere. We are able to identify the nulls both in the tail and in the magnetopause current sheets. On average, we find one null for every few current sheet crossings. We show that the type identification of magnetic nulls may be sensitive to local fluctuations in the magnetic field. We develop and demonstrate a method to estimate the reliability of the magnetic null type identification.

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  • 281. Eriksson, S.
    et al.
    Hasegawa, H.
    Teh, W. -L
    Sonnerup, B. U. Oe.
    McFadden, J. P.
    Glassmeier, K. -H
    Le Contel, O.
    Angelopoulos, V.
    Cully, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Larson, D. E.
    Ergun, R. E.
    Roux, A.
    Carlson, C. W.
    Magnetic island formation between large-scale flow vortices at an undulating postnoon magnetopause for northward interplanetary magnetic field2009In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, no 2, p. A00C17-Article in journal (Refereed)
    Abstract [en]

    Time History of Events and Macroscale Interactions during Substorms multispacecraft observations are presented for a similar to 2-h-long postnoon magnetopause event on 8 June 2007 that for the first time indicate that the trailing (sunward) edges of Kelvin-Helmholtz (KH) waves are commonly related to small-scale < 0.56 R-E magnetic islands or flux transfer events (FTE) during the growth phase of these surface waves. The FTEs typically show a characteristic bipolar B-N structure with enhanced total pressure at their center. Most of the small-scale FTEs are not related to any major plasma acceleration. TH-A observations of one small FTE at a transition from the low-latitude boundary layer (LLBL) into a magnetosheath plasma depletion layer were reconstructed using separate techniques that together confirm the presence of a magnetic island within the LLBL adjacent to the magnetopause. The island was associated with a small plasma vortex and both features appeared between two large-scale (similar to 1 R-E long and 2000 km wide) plasma vortices. We propose that the observed magnetic islands may have been generated from a time-varying reconnection process in a low ion plasma beta (beta(i) < 0.2) and low 8.3 degrees field shear environment at the sunward edge of the growing KH waves where the local magnetopause current sheet may be compressed by the converging flow of the large-scale plasma vortices as suggested by numerical simulations of the KH instability.

  • 282. Eriksson, S.
    et al.
    Lapenta, G.
    Newman, D. L.
    Phan, T. D.
    Gosling, J. T.
    Lavraud, B.
    Khotyaintsev, Yu. V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Carr, C. M.
    Markidis, S.
    Goldman, M. V.
    On Multiple Reconnection X-Lines and Tripolar Perturbations of Strong Guide Magnetic Fields2015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 805, no 1, article id 43Article in journal (Refereed)
    Abstract [en]

    We report new multi-spacecraft Cluster observations of tripolar guide magnetic field perturbations at a solar wind reconnection exhaust in the presence of a guide field B-M. which is almost four times as strong as the reversing field B-L. The novel tripolar field consists of two narrow regions of depressed B-M, with an observed 7%-14% Delta B-M magnitude relative to the external field, which are found adjacent to a wide region of enhanced BM within the exhaust. A stronger reversing field is associated with each B-M depression. A kinetic reconnection simulation for realistic solar wind conditions and the observed strong guide field reveals that tripolar magnetic fields preferentially form across current sheets in the presence of multiple X-lines as magnetic islands approach one another and merge into fewer and larger islands. The simulated Delta B-M/Delta X-N over the normal width Delta X-N between a B-M minimum and the edge of the external region agree with the normalized values observed by Cluster. We propose that a tripolar guide field perturbation may be used to identify candidate regions containing multiple X-lines and interacting magnetic islands at individual solar wind current sheets with a strong guide field.

  • 283.
    Eriksson, S.
    et al.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, Toulouse, France.;CNRS, UMR 5277, Toulouse, France..
    Wilder, F. D.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Stawarz, J. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Baumjohann, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Lindqvist, P. -A
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Pollock, C. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Russell, C. T.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA.;Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Saito, Y.
    Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan..
    Strangeway, R. J.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA.;Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Torbert, R. B.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA.;Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Schwartz, S. J.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.;Imperial Coll London, Blackett Lab, London, England..
    Avanov, L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Grimes, E.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA.;Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Vernisse, Y.
    Univ Toulouse, Inst Rech Astrophys & Planetol, Toulouse, France.;CNRS, UMR 5277, Toulouse, France..
    Sturner, A. P.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Phan, T. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Marklund, G. T.
    Royal Inst Technol, Stockholm, Sweden..
    Moore, T. E.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Goodrich, K. A.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Magnetospheric Multiscale observations of magnetic reconnection associated with Kelvin-Helmholtz waves2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 11, p. 5606-5615Article in journal (Refereed)
    Abstract [en]

    The four Magnetospheric Multiscale (MMS) spacecraft recorded the first direct evidence of reconnection exhausts associated with Kelvin-Helmholtz (KH) waves at the duskside magnetopause on 8 September 2015 which allows for local mass and energy transport across the flank magnetopause. Pressure anisotropy-weighted Walen analyses confirmed in-plane exhausts across 22 of 42 KH-related trailing magnetopause current sheets (CSs). Twenty-one jets were observed by all spacecraft, with small variations in ion velocity, along the same sunward or antisunward direction with nearly equal probability. One exhaust was only observed by the MMS-1,2 pair, while MMS-3,4 traversed a narrow CS (1.5 ion inertial length) in the vicinity of an electron diffusion region. The exhausts were locally 2-D planar in nature as MMS-1,2 observed almost identical signatures separated along the guide-field. Asymmetric magnetic and electric Hall fields are reported in agreement with a strong guide-field and a weak plasma density asymmetry across the magnetopause CS.

  • 284.
    Facsko, G.
    et al.
    Hungarian Acad Sci, Res Ctr Astron & Earth Sci, Geodet & Geophys Inst, Sopron, Hungary.;Finnish Meteorol Inst, FIN-00101 Helsinki, Finland..
    Honkonen, I.
    Finnish Meteorol Inst, FIN-00101 Helsinki, Finland.;NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Zivkovic, T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. DNV GL, Res & Innovat, Hovik, Norway..
    Palin, Laurianne
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Kallio, E.
    Aalto Univ, Sch Elect Engn, Espoo, Finland..
    Ågren, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Opgenoorth, Hermann
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Tanskanen, E. I.
    Aalto Univ, ReSoLVE Ctr Excellence, ELEC Dept Radio Sci & Engn, Espoo, Finland..
    Milan, S.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    One year in the Earth's magnetosphere: A global MHD simulation and spacecraft measurements2016In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 14, no 5, p. 351-367Article in journal (Refereed)
    Abstract [en]

    The response of the Earth's magnetosphere to changing solar wind conditions is studied with a 3-D Magnetohydrodynamic (MHD) model. One full year (155 Cluster orbits) of the Earth's magnetosphere is simulated using Grand Unified Magnetosphere Ionosphere Coupling simulation (GUMICS-4) magnetohydrodynamic code. Real solar wind measurements are given to the code as input to create the longest lasting global magnetohydrodynamics simulation to date. The applicability of the results of the simulation depends critically on the input parameters used in the model. Therefore, the validity and the variance of the OMNIWeb data are first investigated thoroughly using Cluster measurement close to the bow shock. The OMNIWeb and the Cluster data were found to correlate very well before the bow shock. The solar wind magnetic field and plasma parameters are not changed significantly from the L-1 Lagrange point to the foreshock; therefore, the OMNIWeb data are appropriate input to the GUMICS-4. The Cluster SC3 footprints are determined by magnetic field mapping from the simulation results and the Tsyganenko (T96) model in order to compare two methods. The determined footprints are in rather good agreement with the T96. However, it was found that the footprints agree better in the Northern Hemisphere than the Southern one during quiet conditions. If the B-y is not zero, the agreement of the GUMICS-4 and T96 footprint is worse in longitude in the Southern Hemisphere. Overall, the study implies that a 3-D MHD model can increase our insight of the response of the magnetosphere to solar wind conditions.

  • 285.
    Fadanelli, S.
    et al.
    Univ Toulouse, CNES, CNRS, Inst Rech Astrophys & Planetol,UPS, Toulouse, France.;Univ Pisa, Dipartimento Fis, Pisa, Italy..
    Lavraud, B.
    Univ Toulouse, CNES, CNRS, Inst Rech Astrophys & Planetol,UPS, Toulouse, France..
    Califano, F.
    Univ Pisa, Dipartimento Fis, Pisa, Italy..
    Cozzani, Giulia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Univ Pisa, Dipartimento Fis, Pisa, Italy.;Swedish Inst Space Phys, Uppsala, Sweden..
    Finelli, F.
    Univ Pisa, Dipartimento Fis, Pisa, Italy..
    Sisti, M.
    Univ Pisa, Dipartimento Fis, Pisa, Italy.;Aix Marseille Univ, CNRS, PIIM UMR, Marseille, France..
    Energy Conversions Associated With Magnetic Reconnection2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 1, article id e2020JA028333Article in journal (Refereed)
    Abstract [en]

    We present theoretical and computational analyses of energy conversions in a magnetized collisionless plasma. We first revisit the theoretical approach to energy conversion analysis and discuss the expected correlations between the different conversion terms. We then present results from a Hybrid-Vlasov simulation of a turbulent plasma, focusing on the immediate vicinity of a reconnection site. Energy transfers are examined locally and correlations between them are discussed in detail. We show a good anticorrelation between pressure-driven and electromagnetic acceleration terms. A similar but weaker anticorrelation is found between the heat flux and thermodynamic work acting on internal energies. It is the departure from these anticorrelations that drives the effective changes in the species' kinetic and internal energies. We also show that overall energy gain or loss is statistically related to the local scale of the system, with higher conversion rates occurring mostly at the smallest local plasma scales. To summarize, we can say that the energization and de-energization of a plasma is the result of the complex interplay between multiple electromagnetic and thermodynamic effects, which are best taken into account via such a point-by-point analysis of the system.

  • 286.
    Fadanelli, S.
    et al.
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France;Univ Pisa, Dipartimento Fis, Pisa, Italy.
    Lavraud, B.
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France.
    Califano, F.
    Univ Pisa, Dipartimento Fis, Pisa, Italy.
    Jacquey, C.
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France.
    Vernisse, Y.
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France.
    Kacem, I
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France.
    Penou, E.
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France.
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Dorelli, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Pollock, C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Avanov, L. A.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Burch, J.
    Southwest Res Inst, San Antonio, TX USA.
    Chandler, M. O.
    NASA, Marshall Space Flight Ctr, Huntsville, AL USA.
    Coffey, V. N.
    NASA, Marshall Space Flight Ctr, Huntsville, AL USA.
    Eastwood, J. P.
    Imperial Coll London, Dept Phys, Blackett Lab, London, England.
    Ergun, R.
    Univ Colorado Boulder, Lab Atmospher & Space Phys, Boulder, CO USA.
    Farrugia, C. J.
    Univ New Hamsphire, Phys Dept, Durham, NH USA;Univ New Hamsphire, Space Sci Ctr, Durham, NH USA.
    Fuselier, S. A.
    Southwest Res Inst, San Antonio, TX USA;Univ Texas San Antonio, Dept Phys, San Antonio, TX USA.
    Genot, V. N.
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France.
    Grigorenko, E.
    Russian Acad Sci, Space Res Inst, Moscow, Russia.
    Hasegawa, H.
    JAXA, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Le Contel, O.
    Univ Paris Sud, Lab Phys Plasmas, CNRS, Ecole Polytech,Sorbonne Univ,Observ Paris, Paris, France.
    Marchaudon, A.
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France.
    Moore, T. E.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Nakamura, R.
    Space Res Inst, Graz, Austria.
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Phan, T.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.
    Rager, A. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Russell, C. T.
    Univ Calif Los Angeles, Inst Geophys Earth Planetary & Space Sci, Los Angeles, CA USA.
    Saito, Y.
    JAXA, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan.
    Sauvaud, J-A
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France.
    Schiff, C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Smith, S. E.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Redondo, S. Toledo
    Univ Toulouse, CNES, Inst Rech Astrophys & Planetol, CNRS,UPS, Toulouse, France.
    Torbert, R. B.
    Univ New Hamsphire, Phys Dept, Durham, NH USA;Univ New Hamsphire, Space Sci Ctr, Durham, NH USA.
    Wang, S.
    Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
    Yokota, S.
    Osaka Univ, Grad Sch Sci, Toyonaka, Osaka, Japan.
    Four-Spacecraft Measurements of the Shape and Dimensionality of Magnetic Structures in the Near-Earth Plasma Environment2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 8, p. 6850-6868Article in journal (Refereed)
    Abstract [en]

    We present a new method for determining the main relevant features of the local magnetic field configuration, based entirely on the knowledge of the magnetic field gradient four‐spacecraft measurements. The method, named “magnetic configuration analysis” (MCA), estimates the spatial scales on which the magnetic field varies locally. While it directly derives from the well‐known magnetic directional derivative and magnetic rotational analysis procedures (Shi et al., 2005, htpps://doi.org/10.1029/2005GL022454; Shen et al., 2007, https://doi.org/10.1029/2005JA011584), MCA was specifically designed to address the actual magnetic field geometry. By applying MCA to multispacecraft data from the Magnetospheric Multiscale (MMS) satellites, we perform both case and statistical analyses of local magnetic field shape and dimensionality at very high cadence and small scales. We apply this technique to different near‐Earth environments and define a classification scheme for the type of configuration observed. While our case studies allow us to benchmark the method with those used in past works, our statistical analysis unveils the typical shape of magnetic configurations and their statistical distributions. We show that small‐scale magnetic configurations are generally elongated, displaying forms of cigar and blade shapes, but occasionally being planar in shape like thin pancakes (mostly inside current sheets). Magnetic configurations, however, rarely show isotropy in their magnetic variance. The planar nature of magnetic configurations and, most importantly, their scale lengths strongly depend on the plasma β parameter. Finally, the most invariant direction is statistically aligned with the electric current, reminiscent of the importance of electromagnetic forces in shaping the local magnetic configuration.

  • 287.
    Farrell, W. M.
    et al.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.
    Hadid, Lina Z
    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.
    Kurth, W. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    MacDowall, R. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.
    Sulaiman, A. H.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Persoon, A. M.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Saturn's Plasma Density Depletions Along Magnetic Field Lines Connected to the Main Rings2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 16, p. 8104-8110Article in journal (Refereed)
    Abstract [en]

    We report on a set of clear and abrupt decreases in the high-frequency boundary of whistler mode emissions detected by Cassini at high latitudes (about +/- 40 degrees) during the low-altitude proximal flybys of Saturn. These abrupt decreases or dropouts have start and stop locations that correspond to L shells at the edges of the A and B rings. Langmuir probe measurements can confirm, in some cases, that the abrupt decrease in the high-frequency whistler mode boundary is associated with a corresponding abrupt electron density dropout over evacuated field lines connected to the A and B rings. Wideband data also reveal electron plasma oscillations and whistler mode cutoffs consistent with a low-density plasma in the region. The observation of the electron density dropout along ring-connecting field lines suggests that strong ambipolar forces are operating, drawing cold ionospheric ions outward to fill the flux tubes. There is an analog with the refilling of flux tubes in the terrestrial plasmasphere. We suggest that the ring-connected electron density dropouts observed between 1.1 and 1.3 R-s are connected to the low-density ring plasma cavity observed overtop the A and B rings during the 2004 Saturn orbital insertion pass.

    Plain Language Summary We present Cassini observations during the close passes by the planet Saturn indicating that plasma on magnetic field lines that pass through the A and B rings is of anomalously low density. These observations are consistent with the Saturn orbit insertion observations of a plasma cavity located at equatorial regions overtop the dense B ring. Using a terrestrial analogy, we suggest that the low-density conditions overtop the rings create an electrical force, called an ambipolar electric field that draws plasma out of the ionosphere in an attempt to replenish the plasma void found at equatorial regions.

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  • 288. Farrell, W. M.
    et al.
    Kaiser, M. L.
    Gurnett, D. A.
    Kurth, W. S.
    Persoon, A. M.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Canu, P.
    Mass unloading along the inner edge of the Enceladus plasma torus2008In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 35, no 2, p. L02203-Article in journal (Refereed)
    Abstract [en]

    A major discovery made by the Cassini spacecraft at Saturn was the substantial mass ejection from the south pole of Enceladus. Previous studies show that this ejected gas can become ionized and subsequently load mass onto the connecting magnetic field lines near the moon. Radial diffusion then allows the mass-loaded field lines to move outward to similar to 15 R-s and inward to similar to 2 R-s, forming a plasma torus. We demonstrate herein that the mass is also '' unloaded '' along the inner edge of this plasma torus the edge incident with the plasma-absorbing A-ring. Interpreting down-drifting z-mode tones from active sites along the inner edge of the ion torus as emission near the local electron plasma frequency, f(pe), we can remotely-monitor this reduction in plasma density along the torus inner edge as a function time. We find that the down-drift of the z-mode tones corresponds typically to a plasma density change dn/dt similar to - 5x10(-4)/cm(3)-s and when integrated over an annulus defined by the outer edge of the A-ring, corresponds to a mass loss of similar to 40 kg/s. Using the z-mode tones, we also find locations where plasma mass from the ring-ionosphere is possibly loaded at 1 - 2 kg/s onto field lines near the Cassini gap.

  • 289. Farrell, W. M.
    et al.
    Kurth, W. S.
    Gurnett, D. A.
    Johnson, R. E.
    Kaiser, M. L.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Waite, J. H., Jr.
    Electron density dropout near Enceladus in the context of water-vapor and water-ice2009In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 36, no 10, p. L10203-Article in journal (Refereed)
    Abstract [en]

    On 12 March 2008, the Cassini spacecraft made a close encounter with the Saturnian moon Enceladus, passing within 52 km of the moon. The spacecraft trajectory was intentionally-oriented in a southerly direction to create a close alignment with the intense water-dominated plumes emitted from the south polar region. During the passage, the Cassini Radio and Plasma Wave System (RPWS) detected two distinct radio signatures: 1) Impulses associated with small water-ice dust grain impacts and 2) an upper hybrid (UH) resonance emission that both intensified and displayed a sharp frequency decrease in the near-vicinity of the moon. The frequency decrease of the UH emission is associated with an unexpectedly sharp decrease in electron density from similar to 90 cl/cm(3) to below 20 cl/cm(3) that occurs on a time scale of a minute near the closest encounter with the moon. In this work, we consider a number of scenarios to explain this sharp electron dropout, but surmise that electron absorption by ice grains is the most likely process.

  • 290. Farrell, W. M.
    et al.
    Kurth, W. S.
    Tokar, R. L.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gurnett, D. A.
    Wang, Z.
    MacDowall, R. J.
    Morooka, Michiko W.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johnson, R. E.
    Waite, J. H., Jr.
    Modification of the plasma in the near-vicinity of Enceladus by the enveloping dust2010In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 37, no 20, p. L20202-Article in journal (Refereed)
    Abstract [en]

    The plasma near Saturn's equator is quasi-corotating, but those fluid elements entering the near-vicinity of the moon Enceladus become uniquely modified. Besides the solid body, the Moon has a surrounding dust envelop that we show herein to be detected similar to 20 Enceladus radii (1 R-E = 252 km) both north and south of the body. Previous reports indicate that corotating plasma slows down substantially in the near-vicinity of Enceladus. We show herein that the commencement of this plasma slow down matches closely with Cassini's entry into the dense portions of the enveloping dust in the northern hemisphere above the Moon. We also examine in detail the source of the dust about 400 km above the south polar fissures. We find that a large positive potential must exist between the south pole of the moon and the spacecraft to account for ions streaming away from the pole on connecting magnetic field lines.

  • 291. Farrell, W. M.
    et al.
    Wahlund, Jan-Erik
    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, Department of Physics and Astronomy.
    Gurnett, D. A.
    Kurth, W. S.
    MacDowall, R. J.
    An estimate of the dust pickup current at Enceladus2014In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 239, p. 217-221Article in journal (Refereed)
    Abstract [en]

    We demonstrate that the acceleration of submicron dust originating at Enceladus by a reduced co-rotating E-field is capable of creating a dust pickup current perpendicular to the magnetic field with values ranging from 3 to 15 kA (depending upon the effective grain charge). Such a current represents a new contribution to the total pickup current in the region. As such, we suggest that dust pickup currents, along with ion and electron pickup currents, are all active within the plume.

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  • 292.
    Farrell, W. M.
    et al.
    NASA Goddard Space Flight Ctr, Solar Syst Explorat Div, Greenbelt, MD 20771 USA..
    Wahlund, Jan-Erik
    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, Department of Physics and Astronomy.
    Kurth, W. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    MacDowall, R. J.
    NASA Goddard Space Flight Ctr, Solar Syst Explorat Div, Greenbelt, MD 20771 USA..
    Ion trapping by dust grains: Simulation applications to the Enceladus plume2017In: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 122, no 4, p. 729-743Article in journal (Refereed)
    Abstract [en]

    Using a particle-in-cell electrostatic simulation, we examine the conditions that allow low-energy ions, like those produced in the Enceladus plume, to be attracted and trapped within the sheaths of negatively charged dust grains. The conventional wisdom is that all new ions produced in the Enceladus plume are free to get picked up (i.e., accelerated by the local E field to then undergo vB acceleration). However, we suggest herein that the presence of submicron-charged dust in the plume impedes this pickup process since the local grain electric field greatly exceeds the corotation E fields. The simulations demonstrate that cold ions will tend to accelerate toward the negatively charged grains and become part of the ion plasma sheath. These trapped ions will move with the grains, exiting the plume region at the dust speed. We suggest that Cassini's Langmuir probe is measuring the entire ion population (free and trapped ions), while the Cassini magnetometer detects the magnetic perturbations associated with pickup currents from the smaller population of free ions, with this distinction possibly reconciling the ongoing debate in the literature on the ion density in the plume.

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  • 293. Farrell, William M.
    et al.
    Wahlund, Jan-Erik
    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.
    Gurnett, Donald A.
    Kurth, William S.
    MacDowall, Robert J.
    The electromagnetic pickup of submicron-sized dust above Enceladus's northern hemisphere2012In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 219, no 1, p. 498-501Article in journal (Refereed)
    Abstract [en]

    As the saturnian magnetoplasma sweeps past Enceladus, it experiences both a decrease in electron content and sharp slowdown in the northern hemisphere region within similar to 5 Enceladus Radii (R-e). This slowdown is observed by Cassini in regions not obviously associated with the southern directed plume-originating ions. We suggest herein that the decrease in northern hemisphere electron content and plasma slowdown could both be related to the presence of fine dust grains that are being accelerated by the Lorentz force created within the saturnian magnetic field system.

  • 294. Farrugia, C. J.
    et al.
    Chen, Li-Jen
    Torbert, R. B.
    Southwood, D. J.
    Cowley, S. W. H.
    Vrublevskis, A.
    Mouikis, C.
    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, Swedish Institute of Space Physics, Uppsala Division.
    Decreau, P.
    Vaith, H.
    Owen, C. J.
    Sibeck, D. J.
    Lucek, E.
    Smith, C. W.
    "Crater" flux transfer events: Highroad to the X line?2011In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, no 2, p. A02204-Article in journal (Refereed)
    Abstract [en]

    We examine Cluster observations of a so-called magnetosphere "crater FTE," employing data from five instruments (FGM, CIS, EDI, EFW, and WHISPER), some at the highest resolution. The aim of doing this is to deepen our understanding of the reconnection nature of these events by applying recent advances in the theory of collisionless reconnection and in detailed observational work. Our data support the hypothesis of a stratified structure with regions which we show to be spatial structures. We support the bulge-like topology of the core region (R3) made up of plasma jetting transverse to reconnected field lines. We document encounters with a magnetic separatrix as a thin layer embedded in the region (R2) just outside the bulge, where the speed of the protons flowing approximately parallel to the field maximizes: (1) short (fraction of a sec) bursts of enhanced electric field strengths (up to similar to 30 mV/m) and (2) electrons flowing against the field toward the X line at approximately the same time as the bursts of intense electric fields. R2 also contains a density decrease concomitant with an enhanced magnetic field strength. At its interface with the core region, R3, electric field activity ceases abruptly. The accelerated plasma flow profile has a catenary shape consisting of beams parallel to the field in R2 close to the R2/R3 boundary and slower jets moving across the magnetic field within the bulge region. We detail commonalities our observations of crater FTEs have with reconnection structures in other scenarios. We suggest that in view of these properties and their frequency of occurrence, crater FTEs are ideal places to study processes at the separatrices, key regions in magnetic reconnection. This is a good preparation for the MMS mission.

  • 295.
    Farrugia, C. J.
    et al.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Cohen, I. J.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA.
    Vasquez, B. J.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Lugaz, N.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Alm, Love
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Torbert, R. B.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Argall, M. R.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Paulson, K.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Lavraud, B.
    UPMC Univ Paris 06, Univ Paris Sud, Ecole Polytech, LPP,UMR7648,CNRS,Observ Paris, Paris, France.
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Gratton, F. T.
    Acad Nacl Ciencias Buenos Aires, Buenos Aires, DF, Argentina.
    Matsui, H.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Rogers, A.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Forbes, T. G.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Payne, D.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Ergun, R. E.
    Univ Colorado, Boulder, CO 80309 USA.
    Mauk, B.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA.
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA USA.
    Strangeway, R. J.
    Univ Calif Los Angeles, Los Angeles, CA USA.
    Shuster, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Nakamura, R.
    Space Res Inst, Graz, Austria.
    Fuselier, S. A.
    Southwest Res Inst, San Antonio, TX USA;Univ Texas San Antonio, San Antonio, TX USA.
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lindqvist, P. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marklund, Göran T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Petrinec, S. M.
    Lockheed Martin Adv Technol Ctr, Palo Alto, CA USA.
    Pollock, C. J.
    West Virginia Univ, Morgantown, WV USA.
    Effects in the Near-Magnetopause Magnetosheath Elicited by Large-Amplitube Alfvenic Fluctuations Terminating in a Field and Flow Discontinuity2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 11, p. 8983-9004Article in journal (Refereed)
    Abstract [en]

    In this paper we report on a sequence of large-amplitude Alfvenic fluctuations terminating in a field and flow discontinuity and their effects on electromagnetic fields and plasmas in the near-magnetopause magnetosheath. An arc-polarized structure in the magnetic field was observed by the Time History of Events and Macroscale Interactions during Substorms-C in the solar wind, indicative of nonlinear Alfven waves. It ends with a combined tangential discontinuity/vortex sheet, which is strongly inclined to the ecliptic plane and at which there is a sharp rise in the density and a drop in temperature. Several effects resulting from this structure were observed by the Magnetospheric Multiscale spacecraft in the magnetosheath close to the subsolar point (11:30 magnetic local time) and somewhat south of the geomagnetic equator (-33 degrees magnetic latitude): (i) kinetic Alfven waves; (ii) a peaking of the electric and magnetic field strengths where E . J becomes strong and negative (-1 nW/m(3)) just prior to an abrupt dropout of the fields; (iii) evolution in the pitch angle distribution of energetic (a few tens of kilo-electron-volts) ions (H+, Hen+, and On+) and electrons inside a high-density region, which we attribute to gyrosounding of the tangential discontinuity/vortex sheet structure passing by the spacecraft; (iv) field-aligned acceleration of ions and electrons that could be associated with localized magnetosheath reconnection inside the high-density region; and (v) variable and strong flow changes, which we argue to be unrelated to reconnection at partial magnetopause crossings and likely result from deflections of magnetosheath flow by a locally deformed, oscillating magnetopause.

  • 296.
    Farrugia, C. J.
    et al.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys, Toulouse, France.;CNRS, Toulouse, France..
    Torbert, R. B.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Argall, M.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Kacem, I.
    Univ Toulouse, Inst Rech Astrophys, Toulouse, France..
    Yu, W.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Alm, L.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Burch, J.
    Southwest Res Inst, San Antonio, TX USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Shuster, J.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Dorelli, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Eastwood, J. P.
    Imperial Coll London, Blackett Lab, London, England..
    Ergun, R. E.
    Univ Colorado, Boulder, CO 80309 USA..
    Fuselier, S.
    Southwest Res Inst, San Antonio, TX USA.;Univ Texas San Antonio, Dept Space Sci, San Antonio, TX USA..
    Gershman, D.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lindqvist, P. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Matsui, H.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Marklund, G. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Phan, T. D.
    Space Sci Lab, Berkeley, CA USA..
    Paulson, K.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Pollock, C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Magnetospheric Multiscale Mission observations and non-force free modeling of a flux transfer event immersed in a super-Alfvenic flow2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 12, p. 6070-6077Article in journal (Refereed)
    Abstract [en]

    We analyze plasma, magnetic field, and electric field data for a flux transfer event (FTE) to highlight improvements in our understanding of these transient reconnection signatures resulting from high-resolution data. The similar to 20 s long, reverse FTE, which occurred south of the geomagnetic equator near dusk, was immersed in super-Alfvenic flow. The field line twist is illustrated by the behavior of flows parallel/perpendicular to the magnetic field. Four-spacecraft timing and energetic particle pitch angle anisotropies indicate a flux rope (FR) connected to the Northern Hemisphere and moving southeast. The flow forces evidently overcame the magnetic tension. The high-speed flows inside the FR were different from those outside. The external flows were perpendicular to the field as expected for draping of the external field around the FR. Modeling the FR analytically, we adopt a non-force free approach since the current perpendicular to the field is nonzero. It reproduces many features of the observations.

  • 297.
    Farrugia, C. J.
    et al.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Lugaz, N.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Alm, L.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Vasquez, B.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Argall, M. R.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Kucharek, H.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Matsui, H.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Torbert, R. B.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys, Toulouse, France..
    Le Contel, O.
    UPMC Univ Paris 06, Univ Paris Sud, Lab Phys Plasmas, UMR7648,CNRS,Ecole Polytech,Observ Paris, Paris, France..
    Cohen, I. J.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Shuster, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Eastwood, J. P.
    Imperial Coll London, Blackett Lab, London, England..
    Ergun, R. E.
    Univ Colorado Boulder, Lab Atmospher & Space Phys, Boulder, CO USA..
    Fuselier, S. A.
    Southwest Res Inst, San Antonio, TX USA.;Univ Texas San Antonio, Dept Phys, San Antonio, TX USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lindqvist, P. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marklund, G. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Paulson, K. W.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Petrinec, S. M.
    Lockheed Martin Adv Technol Ctr, Palo Alto, CA USA..
    Phan, T. D.
    Space Sci Lab, Berkeley, CA USA..
    Pollock, C. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    MMS Observations of Reconnection at Dayside Magnetopause Crossings During Transitions of the Solar Wind to Sub-Alfvenic Flow2017In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 10, p. 9934-9951Article in journal (Refereed)
    Abstract [en]

    We present MMS observations during two dayside magnetopause crossings under hitherto unexamined conditions: (i) when the bow shock is weakening and the solar wind transitioning to sub-Alfvenic flow and (ii) when it is reforming. Interplanetary conditions consist of a magnetic cloud with (i) a strong B (similar to 20 nT) pointing south and (ii) a density profile with episodic decreases to values of similar to 0.3 cm(-3) followed by moderate recovery. During the crossings the magnetosheath magnetic field is stronger than the magnetosphere field by a factor of similar to 2.2. As a result, during the outbound crossing through the ion diffusion region, MMS observed an inversion of the relative positions of the X and stagnation (S) lines from that typically the case: the S line was closer to the magnetosheath side. The S line appears in the form of a slow expansion fan near which most of the energy dissipation is taking place. While in the magnetosphere between the crossings, MMS observed strong field and flow perturbations, which we argue to be due to kinetic Alfven waves. During the reconnection interval, whistler mode waves generated by an electron temperature anisotropy (T-e perpendicular to > T-e parallel to) were observed. Another aim of the paper is to distinguish bow shock-induced field and flow perturbations from reconnection-related signatures. The high-resolution MMS data together with 2-D hybrid simulations of bow shock dynamics helped us to distinguish between the two sources. We show examples of bow shock-related effects (such as heating) and reconnection effects such as accelerated flows satisfying the Walen relation.

  • 298.
    Feyerabend, Moritz
    et al.
    Univ Cologne, Inst Geophys & Meteorol, Cologne, Germany.;Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA..
    Simon, Sven
    Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA..
    Neubauer, Fritz M.
    Univ Cologne, Inst Geophys & Meteorol, Cologne, Germany..
    Motschmann, Uwe
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Theoret Phys, Braunschweig, Germany.;German Aerosp Ctr, Inst Planetary Res, Berlin, Germany..
    Bertucci, Cesar
    Univ Buenos Aires, CONICET, Inst Astron & Space Phys, Ciudad Univ, Buenos Aires, DF, Argentina..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Hospodarsky, George B.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Kurth, William S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Hybrid simulation of Titan's interaction with the supersonic solar wind during Cassini's T96 flyby2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 1, p. 35-42Article in journal (Refereed)
    Abstract [en]

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

  • 299.
    Fischer, G.
    et al.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Panchenko, M.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Macher, W.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Kasaba, Y.
    Tohoku Univ, Planetary Plasma & Atmospher Res Ctr, Sendai, Miyagi, Japan..
    Misawa, H.
    Tohoku Univ, Planetary Plasma & Atmospher Res Ctr, Sendai, Miyagi, Japan..
    Tokarz, M.
    Astronika, Warsaw, Poland..
    Wisniewski, L.
    Astronika, Warsaw, Poland..
    Cecconi, B.
    PSL, CNRS, Observ Paris, LESIA, Meudon, France..
    Bergman, Jan
    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.
    Calibration of the JUICE RWI Antennas by Numerical Simulation2021In: Radio Science, ISSN 0048-6604, E-ISSN 1944-799X, Vol. 56, no 11, article id e2021RS007309Article in journal (Refereed)
    Abstract [en]

    The reception properties of the Radio Wave Instrument (RWI) onboard JUICE (Jupiter Icy Moons Explorer) have been determined using numerical methods applied to a mesh-grid model of the spacecraft. The RWI is part of the RPWI (Radio and Plasma Wave Investigation) and consists of three perpendicular dipoles mounted on a long boom. We determined their effective lengths vectors and capacitive impedances of 8-9 pF. We also investigated the change in effective antenna angles as a function of solar panel rotation and calculated the directivity of the antennas at higher frequencies up to the maximum frequency of 45 MHz of the receiver. We found that the RWI dipoles can be used for direction-finding with an accuracy of 2 degrees up to a frequency of 1.5 MHz. Additionally we calculated the influence of strong pulses from the JUICE active radar on RPWI and found that they should do no harm to its sensors and receivers.

  • 300.
    Fletcher, Leigh N.
    et al.
    Univ Leicester, Sch Phys & Astron, Univ Rd, Leicester LE1 7RH, England..
    Cavalié, Thibault
    Univ Bordeaux, Lab Astrophys Bordeaux, CNRS, B18N,Allee Geoffroy St Hilaire, F-33615 Pessac, France.;Univ Paris Cite, Sorbonne Univ, Univ PSL, CNRS,LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Grassi, Davide
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Hueso, Ricardo
    Univ Pais Vasco UPV EHU, Escuela Ingn Bilbao, Fis Aplicada, Pl Ingn Torres Quevedo,1, Bilbao 48013, Spain..
    Lara, Luisa M.
    Inst Astrofis Andalucia CSIC, C Glorieta de la Astronomia 3, Granada 18008, Spain..
    Kaspi, Yohai
    Weizmann Inst Sci, Dept Earth & Planetray Sci, IL-76100 Rehovot, Israel..
    Galanti, Eli
    Weizmann Inst Sci, Dept Earth & Planetray Sci, IL-76100 Rehovot, Israel..
    Greathouse, Thomas K.
    Southwest Res Inst, San Antonio, TX 78228 USA..
    Molyneux, Philippa M.
    Southwest Res Inst, San Antonio, TX 78228 USA..
    Galand, Marina
    Imperial Coll London, Dept Phys, Prince Consort Rd, London SW7 2AZ, England..
    Vallat, Claire
    European Space Agcy ESA, ESAC Camino Bajo Castillo, S N Villafranca del Castillo, Villanueva de la Canada 28692, Madrid, Spain..
    Witasse, Olivier
    European Space Agcy ESA, European Space Res & Technol Ctr ESTEC, Noordwijk, Netherlands..
    Lorente, Rosario
    European Space Agcy ESA, ESAC Camino Bajo Castillo, S N Villafranca del Castillo, Villanueva de la Canada 28692, Madrid, Spain..
    Hartogh, Paul
    Max Planck Inst Sonnensystemforschung, D-37077 Gottingen, Germany..
    Poulet, Francois
    Univ Paris Sud, Inst Astrophys Spatiale, CNRS, F-91405 Orsay, France..
    Langevin, Yves
    Univ Paris Sud, Inst Astrophys Spatiale, CNRS, F-91405 Orsay, France..
    Palumbo, Pasquale
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Gladstone, G. Randall
    Southwest Res Inst, San Antonio, TX 78228 USA.;Univ Texas San Antonio, San Antonio, TX USA..
    Retherford, Kurt D.
    Southwest Res Inst, San Antonio, TX 78228 USA.;Univ Texas San Antonio, San Antonio, TX USA..
    Dougherty, Michele K.
    Imperial Coll London, Blackett Lab, London, England..
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Barabash, Stas
    Swedish Inst Space Phys IRF, Kiruna, Sweden..
    Iess, Luciano
    Univ Roma La Sapienza, Dipartimento Ingn Meccan & Aerosp, Rome, Italy..
    Bruzzone, Lorenzo
    Univ Trento, Dept Informat Engn & Comp Sci, Remote Sensing Lab, Via Sommar 14, I-38123 Trento, Italy..
    Hussmann, Hauke
    Deutsch Zent Luft & Raumfahrt DLR, Berlin, Germany..
    Gurvits, Leonid I.
    Joint Inst VLBI ERIC, Oude Hoogeveensedijk 4, NL-7991 PD Dwingeloo, Netherlands.;Delft Univ Technol, Aerosp Fac, Kluyverweg 1, NL-2629 HS Delft, Netherlands..
    Santolik, Ondrej
    Czech Acad Sci, Dept Space Phys, Inst Atmospher Phys, Prague, Czech Republic.;Charles Univ Prague, Fac Math & Phys, Prague, Czech Republic..
    Kolmasova, Ivana
    Czech Acad Sci, Dept Space Phys, Inst Atmospher Phys, Prague, Czech Republic.;Charles Univ Prague, Fac Math & Phys, Prague, Czech Republic..
    Fischer, Georg
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Müller-Wodarg, Ingo
    Imperial Coll London, Blackett Lab, London, England..
    Piccioni, Giuseppe
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Fouchet, Thierry
    Univ Paris Cite, Sorbonne Univ, Univ PSL, CNRS,LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Gérard, Jean-Claude
    Univ Liege, STAR Inst, LPAP, Liege, Belgium..
    Sánchez-Lavega, Agustin
    Univ Pais Vasco UPV EHU, Escuela Ingn Bilbao, Fis Aplicada, Pl Ingn Torres Quevedo,1, Bilbao 48013, Spain..
    Irwin, Patrick G. J.
    Univ Oxford, Atmospher Ocean & Planetary Phys, Dept Phys, Parks Rd, Oxford OX1 3PU, England..
    Grodent, Denis
    Univ Liege, STAR Inst, LPAP, Liege, Belgium..
    Altieri, Francesca
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Mura, Alessandro
    Ist Nazl Astrofis, Ist Astrofis & Planetol Spaziali, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Drossart, Pierre
    Univ Paris Cite, Sorbonne Univ, Univ PSL, CNRS,LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France.;Sorbonne Univ, Inst Astrophys Paris, CNRS, 98bis Blvd Arago, F-75014 Paris, France..
    Kammer, Josh
    Southwest Res Inst, San Antonio, TX 78228 USA..
    Giles, Rohini
    Southwest Res Inst, San Antonio, TX 78228 USA..
    Cazaux, Stéphanie
    Delft Univ Technol, Fac Aerosp Engn, Delft, Netherlands..
    Jones, Geraint
    UCL, Mullard Space Sci Lab, Dorking RH5 6NT, England.;UCL Birkbeck, Ctr Planetary Sci, London WC1E 6BT, England..
    Smirnova, Maria
    Weizmann Inst Sci, Dept Earth & Planetray Sci, IL-76100 Rehovot, Israel..
    Lellouch, Emmanuel
    Univ Paris Cite, Sorbonne Univ, Univ PSL, CNRS,LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Medvedev, Alexander S.
    Max Planck Inst Sonnensystemforschung, D-37077 Gottingen, Germany..
    Moreno, Raphael
    Univ Paris Cite, Sorbonne Univ, Univ PSL, CNRS,LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Rezac, Ladislav
    Max Planck Inst Sonnensystemforschung, D-37077 Gottingen, Germany..
    Coustenis, Athena
    Univ Paris Cite, Sorbonne Univ, Univ PSL, CNRS,LESIA,Observ Paris, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Costa, Marc
    ESAC, European Space Agcy, Rhea Grp, Madrid, Spain..
    Jupiter Science Enabled by ESA's Jupiter Icy Moons Explorer2023In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 219, no 7, article id 53Article, review/survey (Refereed)
    Abstract [en]

    ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible imaging (340-1080 nm), visible/near-infrared spectroscopy (0.49-5.56 & mu;m), and sub-millimetre sounding (near 530-625 GHz and 1067-1275 GHz). This is coupled to radio, stellar, and solar occultation opportunities to explore the atmosphere at high vertical resolution; and radio and plasma wave measurements of electric discharges in the Jovian atmosphere and auroras. Cross-disciplinary scientific investigations enable JUICE to explore coupling processes in giant planet atmospheres, to show how the atmosphere is connected to (i) the deep circulation and composition of the hydrogen-dominated interior; and (ii) to the currents and charged particle environments of the external magnetosphere. JUICE will provide a comprehensive characterisation of the atmosphere and auroras of this archetypal giant planet.

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