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  • 1.
    Aizawa, S.
    et al.
    IRAP, CNRS-CNES-UPS, Toulouse, France; Graduate School of Science, Tohoku University, Sendai, Japan.
    Griton, L.S.
    IRAP, CNRS-CNES-UPS, Toulouse, France; LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, Meudon, France.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, Kiruna, Sweden.
    Exner, W.
    Institute for Geophysics and Extraterrestrial Physics, Technische Universität Braunschweig, Braunschweig, Germany; Institute for Theoretical Physics, Technische Universität Braunschweig, Braunschweig, Germany; School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, United States.
    Deca, J.
    Laboratory for Atmospheric and Space Physics (LASP), University of Colorado Boulder, CO, Boulder, United States; Institute for Modeling Plasma, Atmospheres and Cosmic Dust, NASA/SSERVI, CA, United States; Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles à Saint Quentin, Guyancourt, France.
    Pantellini, F.
    LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, Meudon, France.
    Yagi, M.
    RIKEN, Kobe, Japan.
    Heyner, D.
    Institute for Geophysics and Extraterrestrial Physics, Technische Universität Braunschweig, Braunschweig, Germany.
    Génot, V.
    IRAP, CNRS-CNES-UPS, Toulouse, France.
    André, N.
    IRAP, CNRS-CNES-UPS, Toulouse, France.
    Amaya, J.
    CmPA, Mathematics Department, KU Leuven, Belgium.
    Murakami, G.
    ISAS/JAXA, Sagamihara, Japan.
    Beigbeder, L.
    GFI, Toulouse, France.
    Gangloff, M.
    IRAP, CNRS-CNES-UPS, Toulouse, France.
    Bouchemit, M.
    IRAP, CNRS-CNES-UPS, Toulouse, France.
    Budnik, E.
    Noveltis, Toulouse, France.
    Usui, H.
    Kobe University, Kobe, Japan.
    Cross-comparison of global simulation models applied to Mercury's dayside magnetosphere2021In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 198, article id 105176Article in journal (Refereed)
    Abstract [en]

    We present the first comparison of multiple global simulations of the solar wind interaction with Mercury's dayside magnetosphere, conducted in the framework of the international collaborative project SHOTS - Studies on Hermean magnetosphere Oriented Theories and Simulations. Two 3D magnetohydrodynamic and two 3D hybrid simulation codes are used to investigate the global response of the Hermean magnetosphere without its exosphere to a northward-oriented interplanetary magnetic field. We cross-compare the results of the four codes for a theoretical case and a MESSENGER orbit with similar upstream plasma conditions. The models agree on bowshock and magnetopause locations at 2.1 ​± ​0.11 and 1.4 ​± ​0.1 Mercury planetary radii, respectively. The latter locations may be influenced by subtle differences in the treatment of the plasma boundary at the planetary surface. The predicted magnetosheath thickness varies less between the codes. Finally, we also sample the plasma data along virtual trajectories of BepiColombo's Magnetospheric and Planetary Orbiter. Our ability to accurately predict the structure of the Hermean magnetosphere aids the analysis of the onboard plasma measurements of past and future magnetospheric missions.

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  • 2.
    Behar, Etienne
    et al.
    Solar System Physics And Space Technology, Swedish Institute Of Space Physics, Kiruna, Sweden; Laboratoire Lagrange, Observatoire De La Côte d'Azur, Université Côte d'Azur, Cnrs, Nice, France.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Henri, Pierre
    Laboratoire Lagrange, Observatoire De La Côte d'Azur, Université Côte d'Azur, Cnrs, Nice, France; LPC2E, Orléans, France.
    Holmström, Mats
    Laboratoire Lagrange, Observatoire De La Côte d'Azur, Université Côte d'Azur, Cnrs, Nice, France.
    Menura: A code for simulating the interaction between a turbulent solar wind and solar system bodies2022In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 40, no 3, p. 281-297Article in journal (Refereed)
    Abstract [en]

    Despite the close relationship between planetary science and plasma physics, few advanced numerical tools allow bridging the two topics. The code Menura proposes a breakthrough towards the self-consistent modelling of these overlapping fields, in a novel two-step approach allowing for the global simulation of the interaction between a fully turbulent solar wind and various bodies of the solar system. This article introduces the new code and its two-step global algorithm, illustrated by a first example: the interaction between a turbulent solar wind and a comet.

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  • 3.
    Fatemi, Shahab
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, Kiruna, Sweden.
    Poppe, A. R.
    Barabash, S.
    Hybrid Simulations of Solar Wind Proton Precipitation to the Surface of Mercury2020In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 125, no 4, article id e2019JA027706Article in journal (Refereed)
    Abstract [en]

    We examine the effects of the interplanetary magnetic field (IMF) orientation and solar wind dynamic pressure on the solar wind proton precipitation to the surface of Mercury using a hybrid-kinetic model. We use our model to explain observations of Mercury's neutral sodium exosphere and compare our results with MESSENGER observations. For the typical solar wind dynamic pressure at Mercury our model shows a high proton flux precipitates through the magnetospheric cusps to the high latitudes on both hemispheres on the dayside, centered near the noon meridian with  ∼11° latitudinal extent in the north and ∼21° latitudinal extent in the south, which is consistent with MESSENGER observations. We show that this two-peak pattern is controlled by the radial component (Bx) of the IMF and not the Bz. Our model suggests that the southward IMF and its associated magnetic reconnection do not play a major role in controlling plasma precipitation to the surface of Mercury through the cusps. We found that the total precipitation rate through both of the cusps remain constant and independent of the IMF orientation. We also show that the solar wind proton incidence rate to the entire surface of Mercury is higher when the IMF has a northward component and nearly half of the incidence flux impacts the low latitudes on the nightside. During extreme solar events (e.g., coronal mass ejections), our model suggests that over 70 nPa solar wind dynamic pressure is required for the entire surface of Mercury to be exposed to the solar wind plasma.

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  • 4.
    Fatemi, Shahab
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Poppe, A.R.
    Space Sciences Laboratory, University of California at Berkeley, CA, Berkeley, United States.
    Vorburger, Audrey
    Umeå University, Faculty of Science and Technology, Department of Physics. Physics Institute, University of Bern, Bern, Switzerland.
    Lindkvist, Jesper
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hamrin, Maria
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ion Dynamics at the Magnetopause of Ganymede2022In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 127, no 1, article id e2021JA029863Article in journal (Refereed)
    Abstract [en]

    We study the dynamics of the thermal O+ and H+ ions at Ganymede's magnetopause when Ganymede is inside and outside of the Jovian plasma sheet using a three-dimensional hybrid model of plasma (kinetic ions, fluid electrons). We present the global structure of the electric fields and power density (E ⋅ J) in the magnetosphere of Ganymede and show that the power density at the magnetopause is mainly positive and on average is +0.95 and +0.75 nW/m3 when Ganymede is inside and outside the Jovian plasma sheet, respectively, but locally it reaches over +20 nW/m3. Our kinetic simulations show that ion velocity distributions at the vicinity of the upstream magnetopause of Ganymede are highly non-Maxwellian. We investigate the energization of the ions interacting with the magnetopause and find that the energy of those particles on average increases by a factor of 8 and 30 for the O+ and H+ ions, respectively. The energy of these ions is mostly within 1–100 keV for both species after interaction with the magnetopause, but a few percentages reach to 0.1–1 MeV. Our kinetic simulations show that a small fraction ((Formula presented.) 25%) of the corotating Jovian plasma reach the magnetopause, but among those >50% cross the high-power density regions at the magnetopause and gain energy. Finally, we compare our simulation results with Galileo observations of Ganymede's magnetopause crossings (i.e., G8 and G28 flybys). There is an excellent agreement between our simulations and observations, particularly our simulations fully capture the size and structure of the magnetosphere.

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  • 5.
    Gunell, Herbert
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Goetz, Charlotte
    Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle-upon-Tyne, United Kingdom.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Impact of radial interplanetary magnetic fields on the inner coma of comet 67P/Churyumov-Gerasimenko: Hybrid simulations of the plasma environment2024In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 682, article id A62Article in journal (Refereed)
    Abstract [en]

    Context. The direction of the interplanetary magnetic field determines the nature of the interaction between a Solar System object and the solar wind. For comets, it affects the formation of both a bow shock and other plasma boundaries, as well as mass-loading. Around the nucleus of a comet, there is a diamagnetic cavity, where the magnetic field is negligible. Observations by the Rosetta spacecraft have shown that, most of the time, the diamagnetic cavity is located within a solar-wind ion cavity, which is devoid of solar wind ions. However, solar wind ions have been observed inside the diamagnetic cavity on several occasions. Understanding what determines whether or not the solar wind can reach the diamagnetic cavity also advances our understanding of cometsolar wind interaction in general.

    Aims. We aim to determine the influence of an interplanetary magnetic field directed radially out from the Sun that is, parallel to the solar wind velocity on the cometsolar wind interaction. In particular, we explore the possibility of solar wind protons entering the diamagnetic cavity under radial field conditions.

    Methods. We performed global hybrid simulations of comet 67P/Churyumov-Gerasimenko using the simulation code Amitis for two different interplanetary magnetic field configurations and compared the results to observations made by the Rosetta spacecraft.

    Results. We find that, when the magnetic field is parallel to the solar wind velocity, no bow shock forms and the solar wind ions are able to enter the diamagnetic cavity. A solar wind ion wake still forms further downstream in this case.

    Conclusions. The solar wind can enter the diamagnetic cavity if the interplanetary magnetic field is directed radially from the Sun, and this is in agreement with observations made by instruments on board the Rosetta spacecraft.

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  • 6. Liuzzo, Lucas
    et al.
    Poppe, Andrew R.
    Paranicas, Christopher
    Nenon, Quentin
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, K iruna, Sweden.
    Simon, Sven
    Variability in the Energetic Electron Bombardment of Ganymede2020In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 125, no 9, article id e2020JA028347Article in journal (Refereed)
    Abstract [en]

    This study examines the bombardment of energetic magnetospheric electrons onto Ganymede as a function of Jovian magnetic latitude. We use the output from a three-dimensional, hybrid model to constrain features of the electromagnetic environment during the G1, G8, and G28 Galileo encounters when Ganymede was located far above, within, or far below Jupiter's magnetospheric current sheet, respectively. To quantify electron fluxes, we use a test-particle model and trace relativistic electrons at discrete energies between 4.5 keV =E = 100MeV while exposed to these fields. For each location with respect to Jupiter's current sheet, electrons of all energies bombard Ganymede's poles with average number and energy fluxes of 1 center dot 108 cm-2 s-1 and 3 . 109 keV cm-2 s-1, respectively. However, bombardment is locally inhomogeneous: poleward of the open-closed field line boundary, fluxes are enhanced in the trailing hemisphere but reduced in the leading hemisphere. When embedded within the Jovian current sheet, closed field lines of Ganymede's minimagnetosphere shield electrons below 40MeV from accessing the equator. Above these energies, equatorial fluxes are longitudinally inhomogeneous between the sub-Jovian and anti-Jovian hemispheres, but the averaged number flux (4 . 103 cm-2 s-1) is comparable to the flux deposited here by each of the dominant energetic ion species near Ganymede. When located outside of the Jovian current sheet, electrons below 100 keV enter Ganymede's minimagnetosphere via the downstream reconnection region and bombard the leading apex, while electrons of all energies are shielded from the trailing apex. Averaged over a full synodic rotation period of Jupiter, the energetic electron flux pattern agrees well with brightness features observed across Ganymede's polar and equatorial surface.

  • 7.
    Orsini, S.
    et al.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Milillo, A.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Lichtenegger, H.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Varsani, A.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Barabash, S.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Livi, S.
    Southwest Research Institute, TX, San Antonio, United States; University of Michigan, Department of Climate and Space Sciences and Engineering, MI, Ann Arbor, United States.
    De Angelis, E.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Alberti, T.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Laky, G.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Nilsson, H.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Phillips, M.
    Southwest Research Institute, TX, San Antonio, United States.
    Aronica, A.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Kallio, E.
    Aalto University, Department of Electronics and Nanoengineering, School of Electrical Engineering, Helsinki, Finland.
    Wurz, P.
    University of Bern, Institute of Physics, Bern, Switzerland.
    Olivieri, A.
    Italian Space Agency, ASI, Roma, Italy.
    Plainaki, C.
    Italian Space Agency, ASI, Roma, Italy.
    Slavin, J.A.
    University of Michigan, Department of Climate and Space Sciences and Engineering, MI, Ann Arbor, United States.
    Dandouras, I.
    Institut de Recherche en Astrophysique et Planétologie, CNRS, CNES, Université de Toulouse, Toulouse, France.
    Raines, J.M.
    University of Michigan, Department of Climate and Space Sciences and Engineering, MI, Ann Arbor, United States.
    Benkhoff, J.
    ESA-ESTEC, Noordwijk, Netherlands.
    Zender, J.
    ESA-ESTEC, Noordwijk, Netherlands.
    Berthelier, J.-J.
    LATMOS/IPSL, CNRS, Sorbonne Université, Paris, France.
    Dosa, M.
    Wigner Research Centre for Physics, Budapest, Hungary.
    Ho, G.C.
    The Johns Hopkins University Applied Physics Laboratory, MD, Laurel, United States.
    Killen, R.M.
    NASA/Goddard Space Flight Center, MD, Greenbelt, United States.
    McKenna-Lawlor, S.
    Space Technology Ireland, Ltd., Maynooth, Co., Kildare, Ireland.
    Torkar, K.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Vaisberg, O.
    IKI Space Research Institute, Moscow, Russian Federation.
    Allegrini, F.
    Southwest Research Institute, TX, San Antonio, United States; University of Texas at San Antonio, Department of Physics and Astronomy, TX, San Antonio, United States.
    Daglis, I.A.
    National and Kapodistrian University of Athens, Department of Physics, Athens, Greece; Hellenic Space Center, Athens, Greece.
    Dong, C.
    Princeton Plasma Physics Laboratory and Department of Astrophysical Sciences, Princeton University, NJ, Princeton, United States.
    Escoubet, C.P.
    ESA-ESTEC, Noordwijk, Netherlands.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fränz, M.
    Max-Planck-Institut für Sonnensystemforschung, MPS, Göttingen, Germany.
    Ivanovski, S.
    Astronomincal Observatory, INAF, Trieste, Italy.
    Krupp, N.
    Max-Planck-Institut für Sonnensystemforschung, MPS, Göttingen, Germany.
    Lammer, H.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Leblanc, François
    LATMOS/IPSL, CNRS, Sorbonne Université, Paris, France.
    Mangano, V.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Mura, A.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Rispoli, R.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Sarantos, M.
    NASA/Goddard Space Flight Center, MD, Greenbelt, United States.
    Smith, H.T.
    The Johns Hopkins University Applied Physics Laboratory, MD, Laurel, United States.
    Wieser, M.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Camozzi, F.
    OHB-Italia SpA, Milano, Italy.
    Di Lellis, A.M.
    AMDL srl, Roma, Italy.
    Fremuth, G.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Giner, F.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Gurnee, R.
    Laboratory for Atmospheric and Space Physics, CO, Boulder, United States.
    Hayes, J.
    The Johns Hopkins University Applied Physics Laboratory, MD, Laurel, United States.
    Jeszenszky, H.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Trantham, B.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Balaz, J.
    Institute of Experimental Physics SAS, Slovak Academy of Sciences, Košice, Slovakia.
    Baumjohann, W.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Cantatore, M.
    OHB-Italia SpA, Milano, Italy.
    Delcourt, D.
    Universitè d’Orleans, Orleans, France.
    Delva, M.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Desai, M.
    Southwest Research Institute, TX, San Antonio, United States.
    Fischer, H.
    Max-Planck-Institut für Sonnensystemforschung, MPS, Göttingen, Germany.
    Galli, A.
    University of Bern, Institute of Physics, Bern, Switzerland.
    Grande, M.
    Aberystwyth University, Ceredigion, Aberystwyth, United Kingdom.
    Holmström, M.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Horvath, I.
    Wigner Research Centre for Physics, Budapest, Hungary.
    Hsieh, K.C.
    University of Arizona, AZ, Tucson, United States.
    Jarvinen, R.
    Aalto University, Department of Electronics and Nanoengineering, School of Electrical Engineering, Helsinki, Finland; Finnish Meteorological Institute FMI, Helsinki, Finland.
    Johnson, R.E.
    University of Virginia, VA, Charlottesville, United States.
    Kazakov, A.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Kecskemety, K.
    Wigner Research Centre for Physics, Budapest, Hungary.
    Krüger, H.
    Max-Planck-Institut für Sonnensystemforschung, MPS, Göttingen, Germany.
    Kürbisch, C.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Leblanc, Frederic
    LPP, École polytechnique, Palaiseau Cedex, Paris, France.
    Leichtfried, M.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Mangraviti, E.
    Astronomincal Observatory, INAF, Trieste, Italy.
    Massetti, S.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Moissenko, D.
    IKI Space Research Institute, Moscow, Russian Federation.
    Moroni, M.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Noschese, R.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Nuccilli, F.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Paschalidis, N.
    NASA/Goddard Space Flight Center, MD, Greenbelt, United States.
    Ryno, J.
    Finnish Meteorological Institute FMI, Helsinki, Finland.
    Seki, K.
    University of Tokyo, Department of Earth and Planetary Science, Graduate School of Science, Tokyo, Japan.
    Shestakov, A.
    IKI Space Research Institute, Moscow, Russian Federation.
    Shuvalov, S.
    IKI Space Research Institute, Moscow, Russian Federation.
    Sordini, R.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Stenbeck, F.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Svensson, J.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Szalai, S.
    Wigner Research Centre for Physics, Budapest, Hungary.
    Szego, K.
    Wigner Research Centre for Physics, Budapest, Hungary.
    Toublanc, D.
    Institut de Recherche en Astrophysique et Planétologie, CNRS, CNES, Université de Toulouse, Toulouse, France.
    Vertolli, N.
    Institute of Space Astrophysics and Planetology, INAF, Roma, Italy.
    Wallner, R.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Vorburger, A.
    University of Bern, Institute of Physics, Bern, Switzerland.
    Inner southern magnetosphere observation of Mercury via SERENA ion sensors in BepiColombo mission2022In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 7390Article in journal (Refereed)
    Abstract [en]

    Mercury’s southern inner magnetosphere is an unexplored region as it was not observed by earlier space missions. In October 2021, BepiColombo mission has passed through this region during its first Mercury flyby. Here, we describe the observations of SERENA ion sensors nearby and inside Mercury’s magnetosphere. An intermittent high-energy signal, possibly due to an interplanetary magnetic flux rope, has been observed downstream Mercury, together with low energy solar wind. Low energy ions, possibly due to satellite outgassing, were detected outside the magnetosphere. The dayside magnetopause and bow-shock crossing were much closer to the planet than expected, signature of a highly eroded magnetosphere. Different ion populations have been observed inside the magnetosphere, like low latitude boundary layer at magnetopause inbound and partial ring current at dawn close to the planet. These observations are important for understanding the weak magnetosphere behavior so close to the Sun, revealing details never reached before.

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  • 8.
    Pontoni, Angèle
    et al.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Shimoyama, Manabu
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Futaana, Yoshifumi
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Poppe, A.R.
    Space Sciences Laboratory, University of California, CA, Berkeley, United States.
    Wieser, Martin
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Barabash, Stas
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Simulations of Energetic Neutral Atom Sputtering From Ganymede in Preparation for the JUICE Mission2022In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 127, no 1, article id e2021JA029439Article in journal (Refereed)
    Abstract [en]

    Jovian magnetospheric plasma irradiates the surface of Ganymede and is postulated to be the primary agent that changes the surface brightness of Ganymede, leading to asymmetries between polar and equatorial regions as well as between the trailing and leading hemispheres. As impinging ions sputter surface constituents as neutrals, ion precipitation patterns can be remotely imaged using the Energetic Neutral Atoms (ENA) measurement technique. Here we calculate the expected sputtered ENA flux from the surface of Ganymede to help interpret future observations by ENA instruments, particularly the Jovian Neutrals Analyzer (JNA) onboard the JUpiter ICy moon Explorer (JUICE) spacecraft. We use sputtering models developed based on laboratory experiments to calculate sputtered fluxes of H2O, O2, and H2. The input ion population used in this study is the result of test particle simulations using electric and magnetic fields from a hybrid simulation of Ganymede's environment. This population includes a thermal component (H+ and O+ from 10 eV to 10 keV) and an energetic component (H+, O++, and S+++ from 10 keV to 10 MeV). We find a global ENA sputtering rate from Ganymede of 1.42 × 1027 s−1, with contributions from H2, O2, and H2O of 34%, 17%, and 49% respectively. We also calculate the energy distribution of sputtered Energetic Neutral Atoms (ENAs), give an estimate of a typical JNA count rate at Ganymede, and investigate latitudinal variations of sputtered fluxes along a simulated orbit track of the JUICE spacecraft. Our results demonstrate the capability of the JNA sensor to remotely map ion precipitation at Ganymede.

  • 9. Poppe, A. R.
    et al.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    The solar wind interaction with (1) ceres: The role of interior conductivity2023In: The Planetary Science Journal, E-ISSN 2632-3338, Vol. 4, no 1, article id 14Article in journal (Refereed)
    Abstract [en]

    As a potential "ocean world," (1) Ceres' interior may possess relatively high electrical conductivities on the order of 10(-4)-10(0) S m(-1), suggesting that the solar wind interaction with Ceres may differ from other highly resistive objects such as the Moon. Here, we use a hybrid plasma model to quantify the solar wind interaction with Ceres over a range of scenarios for Ceres' internal conductivity structure and the upstream solar wind and interplanetary magnetic field (IMF) conditions. Internal models for Ceres include one-, two-, and three-layer conductivity structures that variously include a crust, mantle, and/or subsurface ocean, while modeled solar wind conditions include a nominal case, a high IMF case, and an "extreme" space weather case. To first order, Ceres' interaction with the solar wind is governed by the draping and enhancement of the IMF over its interior, whether from a moderate-conductivity mantle or a high-conductivity ocean. In turn, IMF draping induces compressional wings in the solar wind density and deceleration in the solar wind speed outside of Ceres. Together, all three effects are readily observable by a hypothetical orbital or landed mission with standard plasma and magnetic field instrumentation. Finally, we also consider the possible effects of unipolar induction within Ceres, which has been previously suggested as a mechanism for conducting bodies in the solar wind. Our model results show that the efficacy of unipolar induction is highly suppressed by the slow magnetic field-line diffusion through Ceres' interior and, thus, is not a significant contributor to Ceres' overall interaction with the solar wind.

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  • 10.
    Poppe, A.R.
    et al.
    Space Sciences Laboratory, University of California at Berkeley, CA, Berkeley, United States.
    Garrick-Bethell, I.
    Dept. of Earth and Planetary Sciences, University of California, CA, Santa Cruz, United States; School of Space Research, Kyung Hee University, Yongin-si, South Korea.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, Kiruna, Sweden.
    Fractionation of solar wind minor ion precipitation by the lunar paleomagnetosphere2021In: Planetary Science Journal, E-ISSN 2632-3338, Vol. 2, no 2, article id 60Article in journal (Refereed)
    Abstract [en]

    The analysis of solar wind material implanted within lunar soil has provided significant insight into the makeup and evolutionary history of the solar wind and, by extension, the Sun and protosolar nebula. These analyses often rely on the tacit assumption that the Moon has served as an unbiased recorder of solar wind composition over its 4.5 billion yr lifetime. Recent work, however, has shown that for a majority of its lifetime, the Moon has possessed a dynamo that generates a global magnetic field with surface field strengths of at least 5 μT. In turn, the presence of such a field has been shown to significantly alter the lunar–solar wind interaction via the formation of a lunar “paleomagnetosphere.” This paleomagnetosphere has implications for the flux of solar wind minor ions to the lunar surface and their subsequent implantation in lunar soil grains. Here we use a three-dimensional hybrid plasma model to investigate the effects of the lunar paleomagnetosphere on the dynamics and precipitation of solar wind minor ions to the lunar surface. The model results show that the lunar paleomagnetosphere can suppress minor ion fluxes to the lunar surface by more than an order of magnitude and strongly fractionates the precipitating solar wind in a complex, nonlinear fashion with respect to both the minor ion charge-to-mass ratio and the surface paleomagnetic field strength. We discuss the implications of these results with respect to both the analysis of trapped material in lunar grains and the semiquantitative 40Ar/36Ar antiquity indicator for lunar soils.

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  • 11.
    Rasca, Anthony P.
    et al.
    Solar System Exploration Division, NASA/Goddard Space Flight Center, MD, Greenbelt, United States.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Farrell, William M.
    Solar System Exploration Division, NASA/Goddard Space Flight Center, MD, Greenbelt, United States.
    Modeling the Lunar Wake Response to a CME Using a Hybrid PIC Model2022In: Planetary Science Journal, E-ISSN 2632-3338, Vol. 3, no 1, article id 4Article in journal (Refereed)
    Abstract [en]

    In the solar wind, a low-density wake region forms downstream of the nightside lunar surface. In this study, we use a series of 3D hybrid particle-in-cell simulations to model the response of the lunar wake to a passing coronal mass ejection (CME). Average plasma parameters are derived from the Wind spacecraft located at 1 au during three distinct phases of a passing halo (Earth-directed) CME on 2015 June 22. Each set of plasma parameters, representing the shock/plasma sheath, a magnetic cloud, and plasma conditions we call the mid-CME phase, are used as the time-static upstream boundary conditions for three separate simulations. These simulation results are then compared with results that use nominal solar wind conditions. Results show a shortened plasma void compared to nominal conditions and a distinctive rarefaction cone originating from the terminator during the CME’s plasma sheath phase, while a highly elongated plasma void reforms during the magnetic cloud and mid-CME phases. Developments of electric and magnetic field intensification are also observed during the plasma sheath phase along the central wake, while electrostatic turbulence dominates along the plasma void boundaries and 2–3 lunar radii RM downstream in the central wake during the magnetic cloud and mid-CME phases. The simulations demonstrate that the lunar wake responds in a dynamic way with the changes in the upstream solar wind during a CME.

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  • 12.
    Rasca, A.P.
    et al.
    NASA Goddard Space Flight Center, MD, Greenbelt, United States.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Farrell, W.M.
    NASA Goddard Space Flight Center, MD, Greenbelt, United States.
    Poppe, A.R.
    Space Sciences Laboratory, University of California, CA, Berkeley, United States; Solar System Exploration Research Virtual Institute, NASA Ames Research Center, CA, Moffett Field, United States.
    Zheng, Y.
    NASA Goddard Space Flight Center, MD, Greenbelt, United States.
    A Double Disturbed Lunar Plasma Wake2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 2, article id e2020JA028789Article in journal (Refereed)
    Abstract [en]

    Under nominal solar wind conditions, a tenuous wake forms downstream of the lunar nightside. However, the lunar plasma environment undergoes a transformation as the Moon passes through the Earth's magnetotail, with hot subsonic plasma causing the wake structure to disappear. We investigate the lunar wake response during a passing coronal mass ejection (CME) on March 8, 2012 while crossing the Earth's magnetotail using both a magnetohydrodynamic (MHD) model of the terrestrial magnetosphere and a three-dimensional hybrid plasma model of the lunar wake. The CME arrives at 1 AU around 10:30 UT and its impact is first detected inside the geomagnetic tail after 11:10 UT by the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (THEMIS-ARTEMIS) satellites in lunar orbit. A global magnetospheric MHD simulation using Wind data for upstream conditions with the OpenGGCM model reveals the magnetosheath compression to the lunar position from 11:20–12:00 UT, accompanied by multiple flux rope or plasmoid-like features developing and propagating tailward. MHD results support plasma changes observed by the THEMIS-ARTEMIS satellites. Lunar-scale simulations using the Amitis hybrid code show a short and misaligned plasma wake during the Moon's brief entry into the magnetosheath at 11:20 UT, with plasma expansion into the void being aided by the higher plasma temperatures. Sharply accelerated flow speed and a compressed magnetic field lead to an enhanced electric field in the lunar wake capable of generating sudden changes to the nightside near-surface electric potential.

  • 13.
    Shi, Z.
    et al.
    Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China; College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China.
    Rong, Z.J.
    Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China; College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China; Mohe Observatory of Geophysics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Slavin, J.A.
    Department of Climate and Space Sciences and Engineering, University of Michigan, MI, Ann Arbor, United States.
    Klinger, L.
    Beijing International Center for Mathematical Research, Peking University, Beijing, China.
    Dong, C.
    Princeton Plasma Physics Laboratory, Princeton University, NJ, Princeton, United States; Department of Astrophysical Sciences, Princeton University, NJ, Princeton, United States.
    Wang, L.
    Princeton Plasma Physics Laboratory, Princeton University, NJ, Princeton, United States; Department of Astrophysical Sciences, Princeton University, NJ, Princeton, United States.
    Zhong, J.
    Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China; College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China; Mohe Observatory of Geophysics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
    Raines, J.M.
    Department of Climate and Space Sciences and Engineering, University of Michigan, MI, Ann Arbor, United States.
    Holmström, M.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Yuan, C.J.
    Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China; College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China; Mohe Observatory of Geophysics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
    Barabash, S.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Wei, Y.
    Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China; College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China; Mohe Observatory of Geophysics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China.
    An Eastward Current Encircling Mercury2022In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 49, no 10, article id e2022GL098415Article in journal (Refereed)
    Abstract [en]

    Mercury has a terrestrial-like magnetosphere which is usually taken as a scaled-down-version of Earth's magnetosphere with a similar current system. We examine Mercury's magnetospheric current system based on a survey of Mercury's magnetic field measured by the Mercury Surface, Space Environment, Geochemistry, and Ranging spacecraft as well as computer simulations. We show that there is no significant Earth-like ring current flowing westward around Mercury, instead, we find, for the first time, an eastward current (EC) encircling the planet near the night-side magnetic equator with an altitude of ∼500–1,000 km. The EC is closed with the dayside magnetopause current and could be driven by the gradient of plasma pressure as a diamagnetic current. Thus, Mercury's magnetosphere is not a scaled-down Earth magnetosphere, but a unique natural space plasma laboratory. Our findings offer fresh insights to analyze data from the BepiColombo mission, which is expected to orbit Mercury in 2025.

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  • 14.
    Szabo, P.S.
    et al.
    Space Sciences Laboratory, University of California, CA, Berkeley, United States.
    Poppe, A.R.
    Space Sciences Laboratory, University of California, CA, Berkeley, United States.
    Mutzke, A.
    Max Planck Institute for Plasma Physics (IPP), Greifswald, Germany.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vorburger, A.
    Physics Institute, University of Bern, Bern, Switzerland.
    Wurz, P.
    Physics Institute, University of Bern, Bern, Switzerland.
    Energetic neutral atom (ENA) emission characteristics at the moon and mercury from 3D regolith simulations of solar wind reflection2023In: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 128, no 9, article id e2023JE007911Article in journal (Refereed)
    Abstract [en]

    The reflection of solar wind protons as energetic neutral atoms (ENAs) from the lunar surface has regularly been used to study the plasma-surface interaction at the Moon. However, there still exists a fundamental lack of knowledge of the scattering process. ENA emission from the surface is expected to similarly occur at Mercury and will be studied by BepiColombo. Understanding this solar wind backscattering will allow studies of both Mercury's plasma environment as well as properties of the hermean surface itself. Here, we expand on previous simulation studies of the solar-wind-regolith interaction with 3D grains in SDTrimSP-3D to compare the predicted scattering energies and angles to ENA measurements from the Moon by the Chandrayaan-1 and IBEX missions. The simulations reproduce a backward emission toward the Sun, which can be connected to the geometry of the regolith grain stacking. In contrast, the ENA energy distribution and its Maxwellian shape is mostly connected to the solar wind velocity. Our simulations also correctly describe a lunar ENA albedo between 10% and 20% and support its decrease with solar wind velocity. We further expand our studies to illustrate how BepiColombo will be able to observe ENAs at Mercury using hybrid simulations of Mercury's magnetosphere as an input for the complex surface precipitation patterns. We demonstrate that the variable ion precipitation will directly influence ENA emission from the surface. The orbits of BepiColombo's Mercury Planetary Orbiter and Mercury Magnetospheric Orbiter/Mio spacecraft are shown to be suitable to observe ENA emission patterns both on a local and a global scale.

  • 15.
    Szalay, J.R.
    et al.
    Department of Astrophysical Sciences, Princeton University, NJ, Princeton, United States.
    Allegrini, F.
    Southwest Research Institute, TX, San Antonio, United States; Department of Physics and Astronomy, University of Texas at San Antonio, TX, San Antonio, United States.
    Ebert, R.W.
    Southwest Research Institute, TX, San Antonio, United States; Department of Physics and Astronomy, University of Texas at San Antonio, TX, San Antonio, United States.
    Bagenal, F.
    Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, CO, Boulder, United States.
    Bolton, S.J.
    Southwest Research Institute, TX, San Antonio, United States.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    McComas, D.J.
    Department of Astrophysical Sciences, Princeton University, NJ, Princeton, United States.
    Pontoni, A.
    Southwest Research Institute, TX, San Antonio, United States.
    Saur, J.
    Institute of Geophysics and Meteorology, University of Cologne, Cologne, Germany.
    Smith, H.T.
    The Johns Hopkins University Applied Physics Laboratory, MD, Baltimore, United States.
    Strobel, D.F.
    The Johns Hopkins University, MD, Baltimore, United States.
    Vance, S.D.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Vorburger, A.
    Physics Institute, University of Bern, Bern, Switzerland.
    Wilson, R.J.
    Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, CO, Boulder, United States.
    Oxygen production from dissociation of Europa’s water-ice surface2024In: Nature Astronomy, E-ISSN 2397-3366Article in journal (Refereed)
    Abstract [en]

    Jupiter’s moon Europa has a predominantly water-ice surface that is modified by exposure to its space environment. Charged particles break molecular bonds in surface ice, thus dissociating the water to ultimately produce H2 and O2, which provides a potential oxygenation mechanism for Europa’s subsurface ocean. These species are understood to form Europa’s primary atmospheric constituents. Although remote observations provide important global constraints on Europa’s atmosphere, the molecular O2 abundance has been inferred from atomic O emissions. Europa’s atmospheric composition had never been directly sampled and model-derived oxygen production estimates ranged over several orders of magnitude. Here, we report direct observations of H2+ and O2+ pickup ions from the dissociation of Europa’s water-ice surface and confirm these species are primary atmospheric constituents. In contrast to expectations, we find the H2 neutral atmosphere is dominated by a non-thermal, escaping population. We find 12 ± 6 kg s−1 (2.2 ± 1.2 × 1026 s−1) O2 are produced within Europa’s surface, less than previously thought, with a narrower range to support habitability in Europa’s ocean. This process is found to be Europa’s dominant exogenic surface erosion mechanism over meteoroid bombardment.

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  • 16.
    Vorburger, Audrey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Physics Institute, University of Bern, Bern, Switzerland.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Carberry Mogan, Shane R.
    Space Sciences Laboratory, University of California, CA, Berkeley, United States.
    Galli, André
    Physics Institute, University of Bern, Bern, Switzerland.
    Liuzzo, Lucas
    Space Sciences Laboratory, University of California, CA, Berkeley, United States.
    Poppe, Andrew R.
    Space Sciences Laboratory, University of California, CA, Berkeley, United States.
    Roth, Lorenz
    Division of Space and Plasma Physics, KTH Royal Institute of Technology, Stockholm, Sweden.
    Wurz, Peter
    Physics Institute, University of Bern, Bern, Switzerland.
    3D Monte-Carlo simulation of Ganymede's atmosphere2024In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 409, article id 115847Article in journal (Refereed)
    Abstract [en]

    We present new model results for H2O, O2, H2, O, and H in the atmosphere of Ganymede. The results are obtained from a collision-less 3D Monte-Carlo model that includes sublimation, ion and electron sputtering, and ion and electron radiolysis. Because Ganymede has its own magnetic field, its immediate plasma environment is particularly complex. The interaction between Ganymede's and Jupiter's magnetospheres makes it highly variable in both space and time. The recent Juno Ganymede flyby provided us with new data on the electron local environment. Based on the electron measurements recorded by the Jovian Auroral Distributions Experiment (JADE), we implement two electron populations, one for the moon's polar regions and one for the moon's auroral regions. Comparing the atmospheric contribution of these newly defined electron populations to the overall source and loss processes is one of the main goals of this work. Our analysis shows that for H2O, sublimation remains the most important source process even after accounting for the new electron populations, delivering more than three orders of magnitude more H2O molecules to the atmosphere than all other source processes combined. The source fluxes for O2 and H2, on the other hand, are dominated by radiolysis induced by the auroral electrons, assuming that the electron fluxes JADE measured during Juno's transit of Ganymede's magnetopause current layer are representative of auroral electrons. Atomic O and H are mainly added to the atmosphere through the dissociation of O2 and H2, which is primarily induced by auroral electrons. Our understanding of Ganymede's atmosphere today is mainly based on spectroscopic observations. The interpretation of spectroscopic data strongly depends on assumptions taken, though. Our analysis shows that for a holistic understanding of Ganymede's atmosphere, simultaneous observations of the moon's surface, atmosphere, and full plasma environment (thermal and energetic ions and electrons) at different times and locations (both with respect to Ganymede and with respect to Jupiter) are particularly important. Such measurements are planned by ESA's Jupiter ICy moons Explorer (JUICE), in particular by the Particle Environment Package (PEP), which will greatly advance our understanding of Ganymede and its atmosphere and plasma environment.

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  • 17.
    Vorburger, Audrey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Physics Institute, University of Bern, Bern, Switzerland.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Galli, André
    Physics Institute, University of Bern, Bern, Switzerland.
    Liuzzo, Lucas
    Space Sciences Laboratory, University of California, Berkeley, CA, Berkeley, United States.
    Poppe, Andrew R.
    Space Sciences Laboratory, University of California, Berkeley, CA, Berkeley, United States.
    Wurz, Peter
    Physics Institute, University of Bern, Bern, Switzerland.
    3D Monte-Carlo simulation of Ganymede's water exosphere2022In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 375, article id 114810Article in journal (Refereed)
    Abstract [en]

    In this paper we present ab initio 3D Monte-Carlo simulations of Ganymede's surface sputtered and sublimated H2O exosphere. As inputs, we include surface water content maps and temperature distribution maps based on Galileo and Very Large Telescope (VLT) observations. For plasma precipitation, we use hybrid model results for thermal H+ and O+, energetic H+, O++, S+++, and electrons, with unprecedented energy resolution. Our results show that up to a solar zenith angle of ∼60° and up to ∼600 km altitude, sublimated H2O dominates the atmosphere by up to four orders of magnitudes in number density, while sputtering dominates elsewhere. Sputtering is mainly induced by the impinging O+, O++, and S+++ ions, while protons (H+) and electrons only add about 1% of the total sputtered H2O molecules to the atmosphere. Electrons are thus not important for the generation of the atmosphere, but they are important for spectroscopic observability of the atmosphere since they are the main inducer of the Lyman-α and O I emission lines. The extended H2O atmosphere at altitudes ≳1 Ganymede radius is mainly the result of sputtering by thermal O+ ions, which is the only ion species with substantial fluxes in the low-energy range (10 eV–10 keV), i.e., is the only species that efficiently induces nuclear sputtering. Most released H2O molecules return to the surface where they immediately adsorb, not forming a thermalized atmosphere. The morphology of Ganymede's magnetosphere, and the resulting dichotomies in the surface fluxes of the precipitating magnetospheric particles (polar fluxes > equatorial fluxes and leading equatorial fluxes > trailing equatorial fluxes), are thus well discernible in the sputtered atmosphere, persisting up to altitudes of a few thousand kilometers. In-situ measurements, as they are planned for the upcoming JUpiter ICy Moons Explorer (JUICE) mission, will mainly probe this sputtered atmosphere, except for encounters with the near-surface atmosphere on Ganymede's day-side, where the sublimated atmosphere will be probed instead. Finally, we compare our model results to the first observational evidence for a sublimated H2O atmosphere on Ganymede, and find a very good agreement.

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  • 18.
    Wang, Xiao-Dong
    et al.
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Holmström, Mats
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Nilsson, Hans
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Futaana, Yoshifumi
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Barabash, Stas
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Martian global current systems and related solar wind energy transfer: hybrid simulation under nominal conditions2024In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 527, no 4, p. 12232-12242Article in journal (Refereed)
    Abstract [en]

    The magnetized solar wind drives a current system around Mars that maintains its induced magnetosphere. The solar wind also transfers its energy to the atmospheric ions, causing continuous atmospheric erosion, which has a profound impact on the planet’s evolution history. Here, we use Amitis, a Graphics Processing Unit (GPU)-based hybrid plasma model to first reproduce the global pattern of the net electric current and ion currents under an interplanetary magnetic field perpendicular to the solar wind flow direction. The resultant current distribution matches the observations and reveals more details. Using the electric field distribution characterized earlier with the same model, we calculate for the first time the spatial distribution of energy transfer rate to the plasmas in general and to different ion species at Mars. We find out that (1) the solar wind kinetic energy is the dominant energy source that drives Martian induced magnetosphere, (2) the energy flux of the shocked solar wind flows from the magnetic equatorial plane towards the plasma sheet in the induced magnetotail, (3) both the bow shock and the induced magnetospheric boundary are dynamos where plasma energy is transferred to the electromagnetic field, and (4) the planetary ions act as loads and gain energy from the electromagnetic field. The most intense load region is the planetary ion plume. The general pattern of the energy transfer rate revealed in this study is common for induced magnetospheres. Its variabilities with the upstream conditions can provide physical insight into the observed ion escape variabilities.

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  • 19.
    Wang, Xiao-Dong
    et al.
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nilsson, Hans
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Futaana, Yoshifumi
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Holmström, Mats
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Barabash, Stas
    Solar System Physics and Space Technology Programme, Swedish Institute of Space Physics, Kiruna, Sweden.
    Solar wind interaction with Mars: electric field morphology and source terms2023In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 521, no 3, p. 3597-3607Article in journal (Refereed)
    Abstract [en]

    The correlation between space environment conditions and the properties of escaping ions is a central topic of Mars research. Although empirical correlations have been visible in the data, a physics-based interpretation, rather than statistics-based pictures, has not been established yet. As a first effort, we investigate the electric field, the direct contributor to ion acceleration, in the Mars plasma environment from a hybrid plasma model (particle ions and fluid electrons). We use Amitis, a hybrid model combined with an observation-based ionospheric model, to simulate the Mars-solar wind interaction under nominal solar wind plasma conditions for perpendicular and Parker spiral directions of the interplanetary magnetic field (IMF). The simulations show following results: (1) the electric field morphology is structured by the IMF direction and the different plasma domains in the solar wind-Mars interaction; (2) asymmetry of the electric field between the hemispheres where the convective electric field points inward and outward, respectively, due to the mass loading and asymmetric draping of the magnetic field lines; (3) the motional electric field dominates in most regions, especially in the dayside magnetosheath; and (4) the Hall term is an order of magnitude weaker and significant in the magnetotail and plasma boundaries for a perpendicular IMF case. The Hall term is relatively stronger for the Parker spiral case. (5) The ambipolar electric field, in principle, agrees with Mars Atmosphere and Volatile Evolution measurements in the magnetosheath.

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  • 20.
    Wurz, P.
    et al.
    Physics Institute, University of Bern, Bern, Switzerland.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Galli, A.
    Physics Institute, University of Bern, Bern, Switzerland.
    Halekas, J.
    Department of Physics and Astronomy, University of Iowa, IA, Iowa City, United States.
    Harada, Y.
    Kyoto University, Oiwake-cho, Sakyo-ku, Kyoto, Japan.
    Jäggi, N.
    Physics Institute, University of Bern, Bern, Switzerland.
    Jasinski, J.
    NASA Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Lammer, H.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Lindsay, S.
    School of Physics and Astronomy, The University of Leicester, Leicester, United Kingdom.
    Nishino, M.N.
    Japan Aerospace Exploration Agency, Kanagawa, Sagamihara, Japan.
    Orlando, T.M.
    Georgia Institute of Technology, GA, Atlanta, United States.
    Raines, J.M.
    Dept. of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, United States.
    Scherf, M.
    Space Research Institute, Austrian Academy of Sciences, Graz, Austria.
    Slavin, J.
    Dept. of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, United States.
    Vorburger, A.
    Physics Institute, University of Bern, Bern, Switzerland.
    Winslow, R.
    Institute for the Study of Earth, Oceans, and Space, University of New Hamsphire, NH, Durham, United States.
    Particles and Photons as Drivers for Particle Release from the Surfaces of the Moon and Mercury2022In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 218, no 3, article id 10Article, review/survey (Refereed)
    Abstract [en]

    The Moon and Mercury are airless bodies, thus they are directly exposed to the ambient plasma (ions and electrons), to photons mostly from the Sun from infrared range all the way to X-rays, and to meteoroid fluxes. Direct exposure to these exogenic sources has important consequences for the formation and evolution of planetary surfaces, including altering their chemical makeup and optical properties, and generating neutral gas exosphere. The formation of a thin atmosphere, more specifically a surface bound exosphere, the relevant physical processes for the particle release, particle loss, and the drivers behind these processes are discussed in this review.

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