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

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

  • 152. Coates, A.J.
    et al.
    Wahlund, J.-E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Space Plasma Physics.
    Edberg, N.J.T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cui, J.
    Wellbrock, A.
    Szego, K
    Recent results from Titan’s ionosphere2011In: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 162, no 1-4, p. 85-111Article in journal (Refereed)
  • 153.
    Colomban, L.
    et al.
    Univ Orleans, CNRS, LPC2E, CNES, 3A Ave Rech Sci, F-45071 Orleans, France..
    Kretzschmar, M.
    Univ Orleans, CNRS, LPC2E, CNES, 3A Ave Rech Sci, F-45071 Orleans, France..
    Krasnoselkikh, V.
    Univ Orleans, CNRS, LPC2E, CNES, 3A Ave Rech Sci, F-45071 Orleans, France.;Univ Calif Berkeley, Space Sci Lab, Berkeley, CA USA..
    Agapitov, O. V.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA USA.;Natl Taras Shevchenko Univ Kyiv, Astron & Space Phys Dept, Kiev, Ukraine..
    Froment, C.
    Univ Orleans, CNRS, LPC2E, CNES, 3A Ave Rech Sci, F-45071 Orleans, France..
    Maksimovic, M.
    Univ Paris, Sorbonne Univ, Univ PSL, CNRS,LESIA,Observ Paris, Meudon, France..
    Berthomier, M.
    Univ Paris Saclay, Sorbonne Univ, Ecole Polytech, Observ Paris,LPP,CNRS, Paris, France..
    Khotyaintsev, Yuri V.
    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.
    Bale, S.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA USA.;Univ Calif Berkeley, Phys Dept, Berkeley, CA USA..
    Quantifying the diffusion of suprathermal electrons by whistler waves between 0.2 and 1 AU with Solar Orbiter and Parker Solar Probe2024In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 684, article id A143Article in journal (Refereed)
    Abstract [en]

    Context. The evolution of the solar wind electron distribution function with heliocentric distance exhibits different features that are still unexplained, in particular, the fast decrease in the electron heat flux and the increase in the Strahl pitch angle width. Wave-particle interactions between electrons and whistler waves are often proposed to explain these phenomena.

    Aims. We aim to quantify the effect of whistler waves on suprathermal electrons as a function of heliocentric distance.

    Methods. We first performed a statistical analysis of whistler waves (occurrence and properties) observed by Solar Orbiter and Parker Solar Probe between 0.2 and 1 AU. The wave characteristics were then used to compute the diffusion coefficients for solar wind suprathermal electrons in the framework of quasi-linear theory. These coefficients were integrated to deduce the overall effect of whistler waves on electrons along their propagation.

    Results. About 110 000 whistler wave packets were detected and characterized in the plasma frame, including their direction of propagation with respect to the background magnetic field and their radial direction of propagation. Most waves are aligned with the magnetic field and only ∼0.5% of them have a propagation angle greater than 45°. Beyond 0.3 AU, it is almost exclusively quasi-parallel waves propagating anti-sunward (some of them are found sunward but are within switchbacks with a change of sign of the radial component of the background magnetic) that are observed. Thus, these waves are found to be Strahl-aligned and not counter-streaming. At 0.2 AU, we find both Strahl-aligned and counter-streaming quasi-parallel whistler waves.

    Conclusions. Beyond 0.3 AU, the integrated diffusion coefficients show that the observed waves are sufficient to explain the measured Strahl pitch angle evolution and effective in isotropizing the halo. Strahl diffusion is mainly attributed to whistler waves with a propagation angle of θ ∈ [15.45]°, although their origin has not yet been fully determined. Near 0.2 AU, counter-streaming whistler waves are able to diffuse the Strahl electrons more efficiently than the Strahl-aligned waves by two orders of magnitude.

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  • 154.
    Consolini, G.
    et al.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Alberti, T.
    Univ Calabria, Dept Phys, Arcavacata Di Rende, Italy..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marcucci, M. F.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy..
    Echim, M.
    Royal Belgian Inst Space Aeron, Brussels, Belgium.;Inst Space Sci, Magurele, Romania..
    A Hilbert-Huang transform approach to space plasma turbulence at kinetic scales2017In: 16TH ANNUAL INTERNATIONAL ASTROPHYSICS CONFERENCE: TURBULENCE, STRUCTURES, AND PARTICLE ACCELERATION THROUGHOUT THE HELIOSPHERE AND BEYOND / [ed] Zank, G P, IOP PUBLISHING LTD , 2017, article id UNSP 012003Conference paper (Refereed)
    Abstract [en]

    Heliospheric space plasmas are highly turbulent media and display multiscale fluctuations over a wide range of scales from the magnetohydrodynamic domain down to the kinetic one. The study of turbulence features is traditionally based on spectral and canonical structure function analysis. Here, we present an novel approach to the analysis of the multiscale nature of plasma turbulent fluctuations by means of Hilbert-Huang Transform (HHT). In particular we present a preliminary application of this technique to magnetic field fluctuations at kinetic scales in a fast solar wind stream as observed by Cluster mission. The HHT-energy spectrum reveals the intermittent and multiscale nature of fluctuation frequency at kinetic scales indicating that there are no-persistent and long standing frequencies.

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  • 155.
    Consolini, G.
    et al.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy.
    Giannattasio, F.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Voeroes, Z.
    Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Marcucci, M. F.
    INAF Ist Astrofis & Planetol Spaziali, Rome, Italy.
    Echim, M.
    Belgian Inst Aeron, Brussels, Belgium;Inst Space Sci, Magurele, Romania.
    Chang, T.
    MIT, Kavli Inst Astrophys & Space Res, 77 Massachusetts Ave, Cambridge, MA 02139 USA.
    On the scaling features of magnetic field fluctuations at non-MHD scales in turbulent space plasmas2016In: 15th Annual International Astrophysics Conference: "The Science Of Ed Stone: Celebrating His 80Th Birthday" / [ed] Zank, G P, 2016, article id 012003Conference paper (Refereed)
    Abstract [en]

    In several different contexts space plasmas display intermittent turbulence at magneto-hydro-dynamic (MHD) scales, which manifests in anomalous scaling features of the structure functions of the magnetic field increments. Moving to smaller scales, i.e. below the ion-cyclotron and/or ion inertial length, these scaling features are still observed, even though its is not clear if these scaling features are still anomalous or not. Here, we investigate the nature of scaling properties of magnetic field increments at non-MHD scales for a period of fast solar wind to investigate the occurrence or not of multifractal features and collapsing of probability distribution functions (PDFs) using the novel Rank-Ordered Multifractal Analysis (ROMA) method, which is more sensitive than the traditional structure function approach. We find a strong evidence for the occurrence of a near mono-scaling behavior, which suggests that the observed turbulent regime at non-MHD scales mainly displays a mono-fractal nature of magnetic field increments. The results are discussed in terms of a non-compact fractal structure of the dissipation field.

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  • 156. Consolini, G.
    et al.
    Grandioso, S.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Marcucci, M. F.
    Pallocchia, G.
    Statistical and Scaling Features of Fluctuations in the Dissipation Range During a Reconnection Event2015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 804, no 1, article id 19Article in journal (Refereed)
    Abstract [en]

    Reconnection events in space plasmas are accompanied by the occurrence of large-amplitude turbulent fluctuations of the magnetic and electric field, covering a wide range of temporal and spatial scales. Here, we study the scaling and statistical features of magnetic and electric field fluctuations below the ion-gyroperiod (i.e., in the dissipation domain) by carefully investigating the occurrence of local or global scaling features during a reconnection event studied by Eastwood et al. Our results point toward the presence of a global scale invariance, i.e., a mono-fractal nature, of fluctuations above the ion-cyclotron frequency and at spatial scales near the ion-inertial length.

  • 157. Coustenis, A.
    et al.
    Atreya, S. K.
    Balint, T.
    Brown, R. H.
    Dougherty, M. K.
    Ferri, F.
    Fulchignoni, M.
    Gautier, D.
    Gowen, R. A.
    Griffith, C. A.
    Gurvits, L. I.
    Jaumann, R.
    Langevin, Y.
    Leese, M. R.
    Lunine, J. I.
    McKay, C. P.
    Moussas, X.
    Mueller-Wodarg, I.
    Neubauer, F.
    Owen, T. C.
    Raulin, F.
    Sittler, E. C.
    Sohl, F.
    Sotin, C.
    Tobie, G.
    Tokano, T.
    Turtle, E. P.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Waite, J. H.
    Baines, K. H.
    Blamont, J.
    Coates, A. J.
    Dandouras, I.
    Krimigis, T.
    Lellouch, E.
    Lorenz, R. D.
    Morse, A.
    Porco, C. C.
    Hirtzig, M.
    Saur, J.
    Spilker, T.
    Zarnecki, J. C.
    Choi, E.
    Achilleos, N.
    Amils, R.
    Annan, P.
    Atkinson, D. H.
    Benilan, Y.
    Bertucci, C.
    Bezard, B.
    Bjoraker, G. L.
    Blanc, M.
    Boireau, L.
    Bouman, J.
    Cabane, M.
    Capria, M. T.
    Chassefiere, E.
    Coll, P.
    Combes, M.
    Cooper, J. F.
    Coradini, A.
    Crary, F.
    Cravens, T.
    Daglis, I. A.
    de Angelis, E.
    de Bergh, C.
    de Pater, I.
    Dunford, C.
    Durry, G.
    Dutuit, O.
    Fairbrother, D.
    Flasar, F. M.
    Fortes, A. D.
    Frampton, R.
    Fujimoto, M.
    Galand, M.
    Grasset, O.
    Grott, M.
    Haltigin, T.
    Herique, A.
    Hersant, F.
    Hussmann, H.
    Ip, W.
    Johnson, R.
    Kallio, E.
    Kempf, S.
    Knapmeyer, M.
    Kofman, W.
    Koop, R.
    Kostiuk, T.
    Krupp, N.
    Kueppers, M.
    Lammer, H.
    Lara, L. -M
    Lavvas, P.
    Le Mouelic, S.
    Lebonnois, S.
    Ledvina, S.
    Li, J.
    Livengood, T. A.
    Lopes, R. M.
    Lopez-Moreno, J. -J
    Luz, D.
    Mahaffy, P. R.
    Mall, U.
    Martinez-Frias, J.
    Marty, B.
    McCord, T.
    Menor Salvan, C.
    Milillo, A.
    Mitchell, D. G.
    Modolo, Ronan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mousis, O.
    Nakamura, M.
    Neish, C. D.
    Nixon, C. A.
    Nna Mvondo, D.
    Orton, G.
    Paetzold, M.
    Pitman, J.
    Pogrebenko, S.
    Pollard, W.
    Prieto-Ballesteros, O.
    Rannou, P.
    Reh, K.
    Richter, L.
    Robb, F. T.
    Rodrigo, R.
    Rodriguez, S.
    Romani, P.
    Ruiz Bermejo, M.
    Sarris, E. T.
    Schenk, P.
    Schmitt, B.
    Schmitz, N.
    Schulze-Makuch, D.
    Schwingenschuh, K.
    Selig, A.
    Sicardy, B.
    Soderblom, L.
    Spilker, L. J.
    Stam, D.
    Steele, A.
    Stephan, K.
    Strobel, D. F.
    Szego, K.
    Szopa, C.
    Thissen, R.
    Tomasko, M. G.
    Toublanc, D.
    Vali, H.
    Vardavas, I.
    Vuitton, V.
    West, R. A.
    Yelle, R.
    Young, E. F.
    TandEM: Titan and Enceladus mission2009In: Experimental astronomy, ISSN 0922-6435, E-ISSN 1572-9508, Vol. 23, no 3, p. 893-946Article in journal (Refereed)
    Abstract [en]

    TandEM was proposed as an L-class (large) mission in response to ESA's Cosmic Vision 2015-2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini-Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini-Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (MontgolfiSre) and possibly several landing probes to be delivered through the atmosphere.

  • 158.
    Cowley, S. W. H.
    et al.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    Provan, G.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Comment on "Magnetic phase structure of Saturn's 10.7h oscillations" by Yates et al.2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 7, p. 5686-5690Article in journal (Other academic)
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  • 159.
    Cowley, S. W. H.
    et al.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    Zarka, P.
    Univ Paris Diderot, Sorbonne Paris Cite, Univ Paris 06, Univ Paris 04,CNRS,PSL Res Univ,LESIA,Observ Pari, Meudon, France..
    Provan, G.
    Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England..
    Lamy, L.
    Univ Paris Diderot, Sorbonne Paris Cite, Univ Paris 06, Univ Paris 04,CNRS,PSL Res Univ,LESIA,Observ Pari, Meudon, France..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Comment on "A new approach to Saturn's periodicities" by J. F. Carbary2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 3, p. 2418-2422Article in journal (Other academic)
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  • 160.
    Cozzani, G.
    et al.
    Univ Helsinki, Dept Phys, Helsinki, Finland..
    Khotyaintsev, Yuri V.
    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.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Direct Observations of Electron Firehose Fluctuations in the Magnetic Reconnection Outflow2023In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 128, no 5, article id e2022JA031128Article in journal (Refereed)
    Abstract [en]

    Electron temperature anisotropy-driven instabilities such as the electron firehose instability (EFI) are especially significant in space collisionless plasmas, where collisions are so scarce that wave-particle interactions are the leading mechanisms in the isotropization of the distribution function and energy transfer. Observational statistical studies provided convincing evidence in favor of the EFI constraining the electron distribution function and limiting the electron temperature anisotropy. Magnetic reconnection is characterized by regions of enhanced temperature anisotropy that could drive instabilities-including the electron firehose instability-affecting the particle dynamics and the energy conversion. However, in situ observations of the fluctuations generated by the EFI are still lacking and the interplay between magnetic reconnection and EFI is still largely unknown. In this study, we use high-resolution in situ measurements by the Magnetospheric Multiscale spacecraft to identify and investigate EFI fluctuations in the magnetic reconnection exhaust in the Earth's magnetotail. We find that the wave properties of the observed fluctuations largely agree with theoretical predictions of the non-propagating EF mode. These findings are further supported by comparison with the linear kinetic dispersion relation. Our results demonstrate that the magnetic reconnection outflow can be the seedbed of EFI and provide the first direct in situ observations of EFI-generated fluctuations.

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  • 161.
    Cozzani, Giulia
    et al.
    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.
    Graham, Daniel B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Egedal, J.
    Univ Wisconsin, Dept Phys, Madison, WI 53706 USA..
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, A.
    KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Space & Plasma Phys, S-11428 Stockholm, Sweden..
    Alexandrova, A.
    Univ Paris Saclay, Sorbonne Univ, Lab Phys Plasmas, CNRS,Observ Paris,Ecole Polytech,Inst Polytech Pa, F-91128 Palaiseau, France..
    Le Contel, O.
    Univ Paris Saclay, Sorbonne Univ, Lab Phys Plasmas, CNRS,Observ Paris,Ecole Polytech,Inst Polytech Pa, F-91128 Palaiseau, France..
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Fuselier, S. A.
    Southwest Res Inst, San Antonio, TX 78238 USA.;Univ Texas San Antonio, San Antonio, TX 78249 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA 90095 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Structure of a Perturbed Magnetic Reconnection Electron Diffusion Region in the Earth's Magnetotail2021In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 127, no 21, article id 215101Article in journal (Refereed)
    Abstract [en]

    We report in situ observations of an electron diffusion region (EDR) and adjacent separatrix region in the Earth's magnetotail. We observe significant magnetic field oscillations near the lower hybrid frequency which propagate perpendicularly to the reconnection plane. We also find that the strong electron-scale gradients close to the EDR exhibit significant oscillations at a similar frequency. Such oscillations are not expected for a crossing of a steady 2D EDR, and can be explained by a complex motion of the reconnection plane induced by current sheet kinking propagating in the out-of-reconnection-plane direction. Thus, all three spatial dimensions have to be taken into account to explain the observed perturbed EDR crossing. These results shed light on the interplay between magnetic reconnection and current sheet drift instabilities in electron-scale current sheets and highlight the need for adopting a 3D description of the EDR, going beyond the two-dimensional and steady-state conception of reconnection.

  • 162.
    Cozzani, Giulia
    et al.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France;Univ Pisa, Dipartimento Fis E Fermi, I-56127 Pisa, Italy.
    Retino, A.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France.
    Califano, F.
    Univ Pisa, Dipartimento Fis E Fermi, I-56127 Pisa, Italy.
    Alexandrova, A.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France.
    Contel, O. Le
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Fu, H. S.
    Beihang Univ, Sch Space & Environm, Beijing 100083, Peoples R China.
    Catapano, F.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France;Univ Calabria, Dipartimento Fis, I-87036 Arcavacata Di Rende, CS, Italy.
    Breuillard, H.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France;Univ Orleans, UMR 7328, CNRS, Lab Phys & Chim Environm & Espace, F-45071 Orleans, France.
    Ahmadi, N.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.
    Lindqvist, P-A
    KTH Royal Inst Technol, SE-10044 Stockholm, Sweden.
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.
    Torbert, R. B.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA.
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria.
    Fuseher, S.
    Southwest Res Inst, San Antonio, TX 78238 USA;Univ Texas San Antonio, San Antonio, TX 78238 USA.
    Mauk, B. H.
    Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA.
    Moore, T.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA.
    In situ spacecraft observations of a structured electron diffusion region during magnetopause reconnection2019In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 99, no 4, article id 043204Article in journal (Refereed)
    Abstract [en]

    The electron diffusion region (EDR) is the region where magnetic reconnection is initiated and electrons are energized. Because of experimental difficulties, the structure of the EDR is still poorly understood. A key question is whether the EDR has a homogeneous or patchy structure. Here we report Magnetospheric Multiscale (MMS) spacecraft observations providing evidence of inhomogeneous current densities and energy conversion over a few electron inertial lengths within an EDR at the terrestrial magnetopause, suggesting that the EDR can be rather structured. These inhomogenenities are revealed through multipoint measurements because the spacecraft separation is comparable to a few electron inertial lengths, allowing the entire MMS tetrahedron to be within the EDR most of the time. These observations are consistent with recent high-resolution and low-noise kinetic simulations.

  • 163.
    Cravens, T. E.
    et al.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA.
    Moore, L.
    Boston Univ, Ctr Space Phys, Boston, MA 02215 USA.
    Waite, J. H., Jr.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA.
    Perryman, R.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA.
    Perry, M.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Persoon, A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Kurth, W. S.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    The Ion Composition of Saturn's Equatorial Ionosphere as Observed by Cassini2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 12, p. 6315-6321Article in journal (Refereed)
    Abstract [en]

    The Cassini Orbiter made the first in situ measurements of the upper atmosphere and ionosphere of Saturn in 2017. The Ion and Neutral Mass Spectrometer (INMS) found molecular hydrogen and helium as well as minor species including water, methane, ammonia, and organics. INMS ion mode measurements of light ion species (H+, H-2(+), H-3(+), and He+) and Radio and Plasma Wave Science instrument measurements of electron densities are presented. A photochemical analysis of the INMS and Radio and Plasma Wave Science data indicates that the major ion species near the ionospheric peak must be heavy and molecular with a short chemical lifetime. A quantitative explanation of measured H+ and H-3(+) densities requires that they chemically react with one or more heavy neutral molecular species that have mixing ratios of about 100 ppm.

  • 164.
    Cravens, T. E.
    et al.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA.
    Morooka, Michiko
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Renzaglia, A.
    Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA.
    Moore, L.
    Boston Univ, Ctr Space Phys, Boston, MA 02215 USA.
    Waite, J. H., Jr.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA.
    Perryman, R.
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA.
    Perry, M.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Persoon, A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA.
    Hadid, Lina Z
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Plasma Transport in Saturn's Low-Latitude Ionosphere: Cassini Data2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 6, p. 4881-4888Article in journal (Refereed)
    Abstract [en]

    In 2017 the Cassini Orbiter made the first in situ measurements of the upper atmosphere and ionosphere of Saturn. The Ion and Neutral Mass Spectrometer in its ion mode measured densities of light ion species (H+, H-2(+), H-3(+), and He+), and the Radio and Plasma Wave Science instrument measured electron densities. During proximal orbit 287 (denoted P287), Cassini reached down to an altitude of about 3,000 km above the 1 bar atmospheric pressure level. The topside ionosphere plasma densities measured for P287 were consistent with ionospheric measurements during other proximal orbits. Spacecraft potentials were measured by the Radio and Plasma Wave Science Langmuir probe and are typically about negative 0.3 V. Also, for this one orbit, Ion and Neutral Mass Spectrometer was operated in an instrument mode allowing the energies of incident H+ ions to be measured. H+ is the major ion species in the topside ionosphere. Ion flow speeds relative to Saturn's atmosphere were determined. In the southern hemisphere, including near closest approach, the measured ion speeds were close to zero relative to Saturn's corotating atmosphere, but for northern latitudes, southward ion flow of about 3 km/s was observed. One possible interpretation is that the ring shadowing of the southern hemisphere sets up an interhemispheric plasma pressure gradient driving this flow.

  • 165. Cravens, T. E.
    et al.
    Richard, M.
    Ma, Y. -J
    Bertucci, C.
    Luhmann, J. G.
    Ledvina, S.
    Robertson, I. P.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cui, J.
    Muller-Wodarg, I.
    Waite, J. H.
    Dougherty, M.
    Bell, J.
    Ulusen, D.
    Dynamical and magnetic field time constants for Titan's ionosphere: Empirical estimates and comparisons with Venus2010In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, no 8, p. A08319-Article in journal (Refereed)
    Abstract [en]

    Plasma in Titan's ionosphere flows in response to forcing from thermal pressure gradients, magnetic forces, gravity, and ion-neutral collisions. This paper takes an empirical approach to the ionospheric dynamics by using data from Cassini instruments to estimate pressures, flow speeds, and time constants on the dayside and nightside. The plasma flow speed relative to the neutral gas speed is approximately 1 m s(-1) near an altitude of 1000 km and 200 m s(-1) at 1500 km. For comparison, the thermospheric neutral wind speed is about 100 m s(-1). The ionospheric plasma is strongly coupled to the neutrals below an altitude of about 1300 km. Transport, vertical or horizontal, becomes more important than chemistry in controlling ionospheric densities above about 1200-1500 km, depending on the ion species. Empirical estimates are used to demonstrate that the structure of the ionospheric magnetic field is determined by plasma transport (including neutral wind effects) for altitudes above about 1000 km and by magnetic diffusion at lower altitudes. The paper suggests that a velocity shear layer near 1300 km could exist at some locations and could affect the structure of the magnetic field. Both Hall and polarization electric field terms in the magnetic induction equation are shown to be locally important in controlling the structure of Titan's ionospheric magnetic field. Comparisons are made between the ionospheric dynamics at Titan and at Venus.

  • 166. Cravens, T. E.
    et al.
    Robertson, I. P.
    Waite, J. H., Jr.
    Yelle, R. V.
    Vuitton, V.
    Coates, A. J.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Richard, M. S.
    De La Haye, V.
    Wellbrock, A.
    Neubauer, F. M.
    Model-data comparisons for Titan's nightside ionosphere2009In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 199, no 1, p. 174-188Article in journal (Refereed)
    Abstract [en]

    Solar and X-ray radiation and energetic plasma from Saturn's magnetosphere interact with the upper atmosphere producing an ionosphere at Titan. The highly coupled ionosphere and upper atmosphere system mediates the interaction between Titan and the external environment. A model of Titan's nightside ionosphere will be described and the results compared with data from the Ion and Neutral Mass Spectrometer (INMS) and the Langmuir probe (LP) part of the Radio and Plasma Wave (RPWS) experiment for the T5 and T21 nightside encounters of the Cassini Orbiter with Titan. Electron impact ionization associated with the precipitation of magnetospheric electrons into the upper atmosphere is assumed to be the source of the nightside ionosphere, at least for altitudes above 1000 km. Magnetospheric electron fluxes measured by the Cassini electron spectrometer (CAPS ELS) are used as an input for the model. The model is used to interpret the observed composition and structure of the T5 and T21 ionospheres. The densities of many ion species (e.g., CH5+ and C2H5+) measured during T5 exhibit temporal and/or spatial variations apparently associated with variations in the fluxes of energetic electrons that precipitate into the atmosphere from Saturn's magnetosphere.

  • 167.
    Cui, J.
    et al.
    Sun Yat Sen Univ, Sch Atmospher Sci, Zhuhai, Guangdong, Peoples R China;Chinese Acad Sci, Natl Astron Observ, Key Lab Lunar & Deep Space Explorat, Beijing, Peoples R China;Chinese Acad Sci, Ctr Excellence Comparat Planetol, Hefei, Anhui, Peoples R China.
    Cao, Y-T
    Chinese Acad Sci, Natl Astron Observ, Key Lab Lunar & Deep Space Explorat, Beijing, Peoples R China.
    Wu, X-S
    Chinese Acad Sci, Natl Astron Observ, Key Lab Lunar & Deep Space Explorat, Beijing, Peoples R China;Chinese Acad Sci, Ctr Excellence Comparat Planetol, Hefei, Anhui, Peoples R China.
    Xu, S-S
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.
    Yelle, R. , V
    Stone, S.
    Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Shen, C-L
    Chinese Acad Sci, Ctr Excellence Comparat Planetol, Hefei, Anhui, Peoples R China;Univ Sci & Technol China, Sch Earth & Space Sci, Hefei, Anhui, Peoples R China.
    He, F.
    Chinese Acad Sci, Inst Geol & Geophys, Beijing, Peoples R China.
    Wei, Y.
    Chinese Acad Sci, Inst Geol & Geophys, Beijing, Peoples R China.
    Evaluating Local Ionization Balance in the Nightside Martian Upper Atmosphere during MAVEN Deep Dip Campaigns2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 876, no 1, article id L12Article in journal (Refereed)
    Abstract [en]

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

  • 168. Cui, J.
    et al.
    Galand, M.
    Yelle, R. V.
    Vuitton, V.
    Wahlund, Jan Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lavvas, P. P.
    Mueller-Wodarg, I. C. F.
    Cravens, T. E.
    Kasprzak, W. T.
    Waite, J. H., Jr.
    Diurnal variations of Titan's ionosphere2009In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, no 6, p. A06310-Article in journal (Refereed)
    Abstract [en]

    We present our analysis of the diurnal variations of Titan's ionosphere (between 1000 and 1300 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from eight close encounters of the Cassini spacecraft with Titan. Although there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of similar to 700 cm(-3) below similar to 1300 km. Such a plateau is a combined result of significant depletion of light ions and modest depletion of heavy ones on Titan's nightside. We propose that the distinctions between the diurnal variations of light and heavy ions are associated with their different chemical loss pathways, with the former primarily through "fast'' ion-neutral chemistry and the latter through "slow'' electron dissociative recombination. The strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes suggests a scenario in which the ions created on Titan's dayside may survive well to the nightside. The observed asymmetry between the dawn and dusk ion density profiles also supports such an interpretation. We construct a time-dependent ion chemistry model to investigate the effect of ion survival associated with solid body rotation alone as well as superrotating horizontal winds. For long-lived ions, the predicted diurnal variations have similar general characteristics to those observed. However, for short-lived ions, the model densities on the nightside are significantly lower than the observed values. This implies that electron precipitation from Saturn's magnetosphere may be an additional and important contributor to the densities of the short-lived ions observed on Titan's nightside.

  • 169. Cui, J.
    et al.
    Galand, M.
    Yelle, R. V.
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Ågren, K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Waite, J. H., Jr.
    Dougherty, M. K.
    Ion transport in Titan's upper atmosphere2010In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, p. A06314-Article in journal (Refereed)
    Abstract [en]

    Based on a combined Cassini data set including Ion Neutral Mass Spectrometer, Radio Plasma Wave Science, and Magnetometer measurements made during nine close encounters of the Cassini spacecraft with Titan, we investigate the electron ( or total ion) distribution in the upper ionosphere of the satellite between 1250 and 1600 km. A comparison of the measured electron distribution with that in diffusive equilibrium suggests global ion escape from Titan with a total ion loss rate of similar to(1.7 +/- 0.4) x 10(25) s(-1). Significant diurnal variation in ion transport is implied by the data, characterized by ion outflow at the dayside and ion inflow at the nightside, especially below similar to 1400 km. This is interpreted as a result of day-to-night ion transport, with a horizontal transport rate estimated to be similar to(1.4 +/- 0.5) x 10(24) s(-1). Such an ion flow is likely to be an important source for Titan's nightside ionosphere, as proposed in Cui et al. [2009a].

  • 170. Cui, J.
    et al.
    Galand, M.
    Zhang, S. J.
    Vigren, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Zou, H.
    The electron thermal structure in the dayside Martian ionosphere implied by the MGS radio occultation data2015In: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 120, no 2, p. 278-286Article in journal (Refereed)
    Abstract [en]

    We propose a revised Chapman model for the ionosphere of Mars by allowing for vertical variation of electron temperature. An approximate energy balance between solar EUV heating and CO2 collisional cooling is applied in the dayside Martian ionosphere, analogous to the method recently proposed by Withers et al. (2014). The essence of the model is to separate the contributions of the neutral and electron thermal structures to the apparent width of the main ionospheric layer. Application of the model to the electron density profiles from the Mars Global Surveyor (MGS) radio occultation measurements reveals a clear trend of elevated electron temperature with increasing solar zenith angle (SZA). It also reveals that the characteristic length scale for the change of electron temperature with altitude decreases with increasing SZA. These observations may imply enhanced topside heat influx near the terminator, presumably an outcome of the solar wind interactions with the Martian upper atmosphere. Our analysis also reveals a tentative asymmetry in electron temperature between the northern and southern hemispheres, consistent with the scenario of elevated electron temperature within minimagnetospheres.

  • 171.
    Cully, Chris M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Angelopoulos, V.
    Auster, U.
    Bonnell, J.
    Le Contel, O.
    Observational evidence of the generation mechanism for rising-tone chorus2011In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, no 1, p. L01106-Article in journal (Refereed)
    Abstract [en]

    Chorus emissions are a striking feature of the electromagnetic wave environment in the Earth's magnetosphere. These bursts of whistler-mode waves exhibit characteristic frequency sweeps (chirps) believed to result from wave-particle trapping of cyclotron-resonant particles. Based on the theory of Omura et al. (2008), we predict the sweep rates of chorus elements observed by the THEMIS satellites. The predictions use independent observations of the electron distribution functions and have no free parameters. The predicted chirp rates are a function of wave amplitude, and this relation is clearly observed. The predictive success of the theory lends strong support to its underlying physical mechanism: cyclotron-resonant wave-particle trapping.

  • 172.
    Cully, Christopher
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Bonnell, J. W.
    Ergun, R. E.
    THEMIS observations of long-lived regions of large-amplitude whistler waves in the inner magnetosphere2008In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 35, no 17, p. L17S16-Article in journal (Refereed)
    Abstract [en]

    Recent reports of large-amplitude whistler waves (> 100 mV/m) in the radiation belts have intensified interest in the role of whistler waves in accelerating radiation belt electrons to MeV energies. Several critical parameters for addressing this issue have not previously been observed, including the occurrence frequency, spatial extent and longevity of regions of large-amplitude whistlers. The THEMIS mission, with multiple satellites in a near-equatorial orbit, offers an excellent opportunity to study these waves. We use data from the Electric Field Instrument (EFI) to show that in the dawn-side radiation belts, especially near L-shells from 3.5 to 5.5, the probability distribution of wave activity has a significant high-amplitude tail and is hence not well-described by long-term time averages. Regions of enhanced wave activity exhibit four-second averaged wave power above 1 mV/m and sub-second bursts up to several hundred mV/m. These regions are spatially localized to at most several hours of local time azimuthally, but can persist in the same location for several days. With large regions of space persistently covered by bursty, large-amplitude waves, the mechanisms and rates of radiation belt electron acceleration may need to be reconsidered.

  • 173. Cully, C.M.
    et al.
    Ergun, R. E.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Electrostatic structure around spacecraft in tenuous plasmas2007In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 112, no A9, p. A09211-Article in journal (Refereed)
    Abstract [en]

    Most satellite-based in situ plasma experiments are affected in some manner by the electrostatic structure surrounding the spacecraft. In order to better understand this structure, we have developed a fully three-dimensional self-consistent model that can accept realistic spacecraft geometry, including both thin (similar to 10(-4) m) wires and long (similar to 10(2) m) booms, with open boundary conditions. The model uses an integral formulation incorporating boundary element, multigrid and fast multipole methods to overcome problems associated with the large range in scale sizes and inherently three-dimensional structure. By applying the model to the Cluster spacecraft, we show that the electric potential structure is dominated by the charge on the wire booms, with the spacecraft body contributing at small distances. Consequently, the potential near the EFW ( Electric Fields and Waves experiment) probes at the end of the wire booms is typically significantly above the true plasma potential. For the Cluster spacecraft, we show that this effect causes a 19% underestimation of the spacecraft potential and 13% underestimation of the ambient electric field. We further assess the electric field due to the sunward-oriented photoelectron cloud, showing that the cloud contributes little to the observed spurious sunward field in the EFW data.

  • 174.
    Dai, Lei
    et al.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Wang, Chi
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Cai, Zhiming
    Chinese Acad Sci, Innovat Acad Microsatellites, Shanghai, Peoples R China..
    Gonzalez, Walter
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China.;Natl Inst Space Res INPE, Sao Jose Dos Campos, Brazil..
    Hesse, Michael
    Univ Bergen, Dept Phys & Technol, Bergen, Norway.;Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA..
    Escoubet, Philippe
    European Space Agcy ESA, European Space Res & Technol Ctr, Noordwijk, Netherlands..
    Phan, Tai
    Vasyliunas, Vytenis
    Max Planck Inst Solar Syst Res, Gottingen, Germany..
    Lu, Quanming
    Univ Sci & Technol China, Dept Geophys & Planetary Sci, Hefei, Peoples R China..
    Li, Lei
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Kong, Linggao
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Dunlopla, Malcolm
    Rutherford Appleton Lab, Sci & Technol Facil Council STFC, Didcot, Oxon, England.;Beihang Univ, Sch Space & Environm, Beijing, Peoples R China..
    Nakamura, Rumi
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    He, Jianshen
    Beijing Univ, Beijing, Peoples R China..
    Fu, Huishan
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China..
    Zhou, Meng
    Nanchang Univ, Inst Space Sci & Technol, Nanchang, Jiangxi, Peoples R China..
    Huang, Shiyong
    Wuhan Univ, Sch Elect & Informat, Wuhan, Peoples R China..
    Wang, Rongsheng
    Univ Sci & Technol China, Dept Geophys & Planetary Sci, Hefei, Peoples R China..
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Graham, Daniel
    Swedish Inst Space Phys, Uppsala, Sweden..
    Retino, Alessandro
    Ecole Polytech, Lab Phys Plasmas LPP, Palaiseau, France..
    Zelenyi, Lev
    Russian Acad Sci, Space Res Inst, Moscow, Russia..
    Grigorenko, Elena E.
    Russian Acad Sci, Space Res Inst, Moscow, Russia..
    Runov, Andrei
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Angelopoulos, Vassilis
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Kepko, Larry
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Hwang, Kyoung-Joo
    Southwest Res Inst, Space Sci & Engn Div, San Antonio, TX USA..
    Zhang, Yongcun
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    AME: A Cross-Scale Constellation of CubeSats to Explore Magnetic Reconnection in the Solar-Terrestrial Relation2020In: Frontiers in Physics, E-ISSN 2296-424X, Vol. 8, article id 89Article in journal (Refereed)
    Abstract [en]

    A major subset of solar-terrestrial relations, responsible, in particular, for the driver of space weather phenomena, is the interaction between the Earth's magnetosphere and the solar wind. As one of the most important modes of the solar-wind-magnetosphere interaction, magnetic reconnection regulates the energy transport and energy release in the solar-terrestrial relation. In situ measurements in the near-Earth space are crucial for understanding magnetic reconnection. Past and existing spacecraft constellation missions mainly focus on the measurement of reconnection on plasma kinetic-scales. Resolving the macro-scale and cross-scale aspects of magnetic reconnection is necessary for accurate assessment and predictions of its role in the context of space weather. Here, we propose the AME (self-Adaptive Magnetic reconnection Explorer) mission consisting of a cross-scale constellation of 12+ CubeSats and one mother satellite. Each CubeSat is equipped with instruments to measure magnetic fields and thermal plasma particles. With multiple CubeSats, the AME constellation is intended to make simultaneous measurements at multiple scales, capable of exploring cross-scale plasma processes ranging from kinetic scale to macro scale.

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  • 175.
    D'Amicis, R.
    et al.
    Natl Inst Astrophys INAF, Inst Space Astrophys & Planetol IAPS, Via Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Bruno, R.
    Natl Inst Astrophys INAF, Inst Space Astrophys & Planetol IAPS, Via Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Panasenco, O.
    Adv Heliophys, Pasadena, CA USA..
    Telloni, D.
    Natl Inst Astrophys INAF, Natl Observ Turin OATo, Via Osservatorio, Turin, Italy..
    Perrone, D.
    Italian Space Agcy ASI, Via Politecn Snc, I-00133 Rome, Italy..
    Marcucci, M. F.
    Natl Inst Astrophys INAF, Inst Space Astrophys & Planetol IAPS, Via Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Woodham, L.
    Imperial Coll London, Dept Phys, London SW7 2AZ, England..
    Velli, M.
    UCLA, Earth Planetary & Space Sci Dept, Los Angeles, CA USA..
    De Marco, R.
    Natl Inst Astrophys INAF, Inst Space Astrophys & Planetol IAPS, Via Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Jagarlamudi, V
    Natl Inst Astrophys INAF, Inst Space Astrophys & Planetol IAPS, Via Fosso del Cavaliere 100, I-00133 Rome, Italy..
    Coco, I
    Ist Nazl Geofis & Vulcanol INGV, Via Vigna Murata 605, I-00143 Rome, Italy..
    Owen, C.
    Mullard Space Sci Lab, Holmbury RH5 6NT, St Mary, England..
    Louarn, P.
    Univ Toulouse III Paul Sabatier, Inst Rech Astrophys & Planetol, CNES, CNRS, Toulouse, France..
    Livi, S.
    Southwest Res Inst, San Antonio, TX USA..
    Horbury, T.
    Imperial Coll London, Dept Phys, London SW7 2AZ, England..
    Andre, N.
    Univ Toulouse III Paul Sabatier, Inst Rech Astrophys & Planetol, CNES, CNRS, Toulouse, France..
    Angelini, V
    Imperial Coll London, Dept Phys, London SW7 2AZ, England..
    Evans, V
    Imperial Coll London, Dept Phys, London SW7 2AZ, England..
    Fedorov, A.
    Univ Toulouse III Paul Sabatier, Inst Rech Astrophys & Planetol, CNES, CNRS, Toulouse, France..
    Genot, V
    Univ Toulouse III Paul Sabatier, Inst Rech Astrophys & Planetol, CNES, CNRS, Toulouse, France..
    Lavraud, B.
    Univ Toulouse III Paul Sabatier, Inst Rech Astrophys & Planetol, CNES, CNRS, Toulouse, France.;Univ Bordeaux, Lab Astrophys Bordeaux, CNRS, Pessac, France..
    Matteini, L.
    Imperial Coll London, Dept Phys, London SW7 2AZ, England..
    Muller, D.
    ESTEC SCI S, European Space Agcy, 299, NL-2200 AG Noordwijk, Netherlands..
    O'Brien, H.
    Imperial Coll London, Dept Phys, London SW7 2AZ, England..
    Pezzi, O.
    Gran Sasso Sci Inst GSSI, Viale F Crispi 7, I-67100 Laquila, Italy.;INFN Lab Nazl Gran Sasso, Via G Acitelli 22, I-67100 Laquila, Italy.;CNR, Ist Sci & Tecnol Plasmi, Via Amendola 112-D, I-70126 Bari, Italy..
    Rouillard, A. P.
    Univ Toulouse III Paul Sabatier, Inst Rech Astrophys & Planetol, CNES, CNRS, Toulouse, France..
    Sorriso-Valvo, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR, Ist Sci & Tecnol Plasmi, Via Amendola 112-D, I-70126 Bari, Italy.
    Tenerani, A.
    Univ Texas Austin, 2515 Speedway, Austin, TX 78712 USA..
    Verscharen, D.
    Mullard Space Sci Lab, Holmbury RH5 6NT, St Mary, England.;Univ New Hampshire, Space Sci Ctr, 8 Coll Rd, Durham, NH 03824 USA..
    Zouganelis, I
    European Space Astron Ctr ESAC, European Space Agcy ESA, Camino Bajo del Castillo S-N, Madrid 28692, Spain..
    First Solar Orbiter observation of the Alfvenic slow wind and identification of its solar source2021In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 656, article id A21Article in journal (Refereed)
    Abstract [en]

    Context. Turbulence dominated by large-amplitude, nonlinear Alfven-like fluctuations mainly propagating away from the Sun is ubiquitous in high-speed solar wind streams. Recent studies have demontrated that slow wind streams may also show strong Alfvenic signatures, especially in the inner heliosphere.

    Aims. The present study focuses on the characterisation of an Alfvenic slow solar wind interval observed by Solar Orbiter between 14 and 18 July 2020 at a heliocentric distance of 0.64 AU.

    Methods. Our analysis is based on plasma moments and magnetic field measurements from the Solar Wind Analyser (SWA) and Magnetometer (MAG) instruments, respectively. We compared the behaviour of different parameters to characterise the stream in terms of the Alfvenic content and magnetic properties. We also performed a spectral analysis to highlight spectral features and waves signature using power spectral density and magnetic helicity spectrograms, respectively. Moreover, we reconstruct the Solar Orbiter magnetic connectivity to the solar sources both via a ballistic and a potential field source surface (PFSS) model.

    Results. The Alfvenic slow wind stream described in this paper resembles, in many respects, a fast wind stream. Indeed, at large scales, the time series of the speed profile shows a compression region, a main portion of the stream, and a rarefaction region, characterised by different features. Moreover, before the rarefaction region, we pinpoint several structures at different scales recalling the spaghetti-like flux-tube texture of the interplanetary magnetic field. Finally, we identify the connections between Solar Orbiter in situ measurements, tracing them down to coronal streamer and pseudostreamer configurations.

    Conclusions. The characterisation of the Alfvenic slow wind stream observed by Solar Orbiter and the identification of its solar source are extremely important aspects for improving the understanding of future observations of the same solar wind regime, especially as solar activity is increasing toward a maximum, where a higher incidence of this solar wind regime is expected.

  • 176.
    D'Amicis, Raffaella
    et al.
    INAF Inst Space Astrophys & Planetol, I-00133 Rome, Italy..
    Perrone, Denise
    Italian Space Agcy ASI, I-00133 Rome, Italy..
    Velli, Marco
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA..
    Sorriso-Valvo, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. CNR, Ist Sci & Tecnol Plasmi, I-70126 Bari, Italy..
    Telloni, Daniele
    INAF Osservatorio Astrofis Torino, I-10025 Pino Torinese, Italy..
    Bruno, Roberto
    INAF Inst Space Astrophys & Planetol, I-00133 Rome, Italy..
    De Marco, Rossana
    INAF Inst Space Astrophys & Planetol, I-00133 Rome, Italy..
    Investigating Alfvenic Turbulence in Fast and Slow Solar Wind Streams2022In: Universe, E-ISSN 2218-1997, Vol. 8, no 7, article id 352Article in journal (Refereed)
    Abstract [en]

    Solar wind turbulence dominated by large-amplitude Alfvenic fluctuations, mainly propagating away from the Sun, is ubiquitous in high-speed solar wind streams. Recent observations performed in the inner heliosphere (from 1 AU down to tens of solar radii) have proved that also slow wind streams show sometimes strong Alfvenic signatures. Within this context, the present paper focuses on a comparative study on the characterization of Alfvenic turbulence in fast and slow solar wind intervals observed at 1 AU where degradation of Alfvenic correlations is expected. In particular, we compared the behavior of different parameters to characterize the Alfvenic content of the fluctuations, using also the Elsasser variables to derive the spectral behavior of the normalized cross-helicity and residual energy. This study confirms that the Alfvenic slow wind stream resembles, in many respects, a fast wind stream. The velocity-magnetic field (v-b) correlation coefficient is similar in the two cases as well as the amplitude of the fluctuations although it is not clear to what extent the condition of incompressibility holds. Moreover, the spectral analysis shows that fast wind and Alfvenic slow wind have similar normalized cross-helicity values but in general the fast wind streams are closer to energy equipartition. Despite the overall similarities between the two solar wind regimes, each stream shows also peculiar features, that could be linked to the intrinsic evolution history that each of them has experienced and that should be taken into account to investigate how and why Alfvenicity evolves in the inner heliosphere.

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  • 177. Dandouras, Iannis
    et al.
    Garnier, Philippe
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mitchell, Donald G.
    Roelof, Edmond C.
    Brandt, Pontus C.
    Krupp, Norbert
    Krimigis, Stamatios M.
    Titan's exosphere and its interaction with Saturn's magnetosphere2009In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 367, no 1889, p. 743-752Article in journal (Refereed)
    Abstract [en]

    Titan's nitrogen-rich atmosphere is directly bombarded by energetic ions, due to its lack of a significant intrinsic magnetic field. Singly charged energetic ions from Saturn's magnetosphere undergo charge-exchange collisions with neutral atoms in Titan's upper atmosphere, or exosphere, being transformed into energetic neutral atoms (ENAs). The ion and neutral camera, one of the three sensors that comprise the magnetosphere imaging instrument (MIMI) on the Cassini/Huygens mission to Saturn and Titan, images these ENAs like photons, and measures their fluxes and energies. These remote-sensing measurements, combined with the in situ measurements performed in the upper thermosphere and in the exosphere by the ion and neutral mass spectrometer instrument, provide a powerful diagnostic of Titan's exosphere and its interaction with the Kronian magnetosphere. These observations are analysed and some of the exospheric features they reveal are modelled.

  • 178.
    De Keyser, J.
    et al.
    Royal Belgian Inst Space Aeron BIRA IASB, Space Phys Div, Ringlaan 3, B-1180 Brussels, Belgium.;Katholieke Univ Leuven, Ctr Math Plasma Astrophys, Celestijnenlaan 200B, B-3001 Heverlee, Belgium..
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Henri, P.
    CNRS, Lab Phys & Chim Environm & Espace LPC2E, Orleans, France.;Univ Cote Azur OCA, Lab Lagrange, Observ Cote Azur, CNRS, Nice, France..
    Auster, H. -U
    Galand, M.
    Imperial Coll London ICL, Dept Surg & Canc, London, England..
    Rubin, M.
    Univ Bern, Phys Inst, Space Res & Planetary Sci, Bern, Switzerland..
    Nilsson, H.
    Swedish Inst Space Phys IRF, Kiruna, Sweden..
    Soucek, J.
    Inst Atmospher Phys CAS, Dept Space Phys, Prague, Czech Republic..
    Andre, N.
    UPS, CNRS, Inst Rech Astrophys & Planetol, CNES, Toulouse, France..
    Della Corte, V.
    INAF Ist Astrofis & Planetol Spaziali INAF IAPS, Uppsala, Italy..
    Rothkaehl, H.
    Polish Acad Sci, CBK, Warsaw, Poland..
    Funase, R.
    Inst Space & Astronaut Sci, Japan Aerosp Explorat Agcy, Sagamihara, Japan..
    Kasahara, S.
    Univ Tokyo, Dept Earth & Planetary Sci, Tokyo, Japan..
    Van Dammep, C. Corral
    ESTEC, European Space Agcy, Noordwijk, Netherlands..
    In situ plasma and neutral gas observation time windows during a comet flyby: Application to the Comet Interceptor mission2024In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 244, article id 105878Article in journal (Refereed)
    Abstract [en]

    A comet flyby, like the one planned for ESA's Comet Interceptor mission, places stringent requirements on spacecraft resources. To plan the time line of in situ plasma and neutral gas observations during the flyby, the size of the comet magnetosphere and neutral coma must be estimated well. For given solar irradiance and solar wind conditions, comet composition, and neutral gas expansion speed, the size of gas coma and magnetosphere during the flyby can be estimated from the gas production rate and the flyby geometry. Combined with flyby velocity, the time spent in these regions can be inferred and a data acquisition plan can be elaborated for each instrument, compatible with the limited data storage capacity. The sizes of magnetosphere and gas coma are found from a statistical analysis based on the probability distributions of gas production rate, flyby velocity, and solar wind conditions. The size of the magnetosphere as measured by bow shock standoff distance is 105-106 km near 1 au in the unlikely case of a Halley-type target comet, down to a nonexistent bow shock for targets with low activity. This translates into durations up to 103-104 seconds. These estimates can be narrowed down when a target is identified far from the Sun, and even more so as its activity can be predicted more reliably closer to the Sun. Plasma and neutral gas instruments on the Comet Interceptor main spacecraft can monitor the entire flyby by using an adaptive data acquisition strategy in the context of a record-and-playback scenario. For probes released from the main spacecraft, the inter-satellite communication link limits the data return. For a slow flyby of an active comet, the probes may not yet be released during the inbound bow shock crossing.

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  • 179. Deca, J.
    et al.
    Divin, Andrey
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Lapenta, G.
    Lembege, B.
    Markidis, S.
    Horanyi, M.
    Electromagnetic Particle-in-Cell Simulations of the Solar Wind Interaction with Lunar Magnetic Anomalies2014In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 112, no 15, p. 151102-Article in journal (Refereed)
    Abstract [en]

    We present the first three-dimensional fully kinetic and electromagnetic simulations of the solar wind interaction with lunar crustal magnetic anomalies (LMAs). Using the implicit particle-in-cell code IPIC3D, we confirm that LMAs may indeed be strong enough to stand off the solar wind from directly impacting the lunar surface forming a mini-magnetosphere, as suggested by spacecraft observations and theory. In contrast to earlier magnetohydrodynamics and hybrid simulations, the fully kinetic nature of IPIC3D allows us to investigate the space charge effects and in particular the electron dynamics dominating the near-surface lunar plasma environment. We describe for the first time the interaction of a dipole model centered just below the lunar surface under plasma conditions such that only the electron population is magnetized. The fully kinetic treatment identifies electromagnetic modes that alter the magnetic field at scales determined by the electron physics. Driven by strong pressure anisotropies, the mini-magnetosphere is unstable over time, leading to only temporal shielding of the surface underneath. Future human exploration as well as lunar science in general therefore hinges on a better understanding of LMAs.

  • 180.
    Deca, Jan
    et al.
    Univ Colorado, Atmospher & Space Phys Lab, Campus Box 392, Boulder, CO 80309 USA.;NASA SSERVI, Inst Modeling Plasma Atmospheres & Cosm Dust, Boulder, CO 80301 USA..
    Divin, Andrey
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. St Petersburg State Univ, Dept Phys, St Petersburg, Russia..
    Reflected Charged Particle Populations Around Dipolar Lunar Magnetic Anomalies2016In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 829, no 2, article id 60Article in journal (Refereed)
    Abstract [en]

    In this work we analyze and compare the reflected particle populations for both a horizontal and a vertical dipole model embedded in the lunar surface, representing the solar wind interaction with two different lunar magnetic anomaly (LMA) structures. Using the 3D full-kinetic electromagnetic code iPic3D, in combination with a test-particle approach to generate particle trajectories, we focus on the ion and electron dynamics. Whereas the vertical model electrostatically reflects ions upward under both near-parallel and near-perpendicular angles with respect to the lunar surface, the horizontal model only has a significant shallow component. Characterizing the electron dynamics, we find that the interplay of the mini-magnetosphere electric and magnetic fields is capable of temporarily trapping low-energy electrons and possibly ejecting them upstream. Our results are in agreement with recent high-resolution observations. Low-to medium-altitude ion and electron observations might be excellent indicators to complement orbital magnetic field measurements and better uncover the underlying magnetic field structure. The latter is of particular importance in defining the correlation between LMAs and lunar swirls, and further testing the solar wind shielding hypothesis for albedo markings due to space weathering. Observing more reflected ions does not necessarily point to the existence of a mini-magnetosphere.

  • 181.
    Deca, Jan
    et al.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA.;NASA, SSERVI, Inst Modeling Plasma Atmospheres & Cosm Dus, Moffett Field, CA 94035 USA..
    Divin, Andrey
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. St Petersburg State Univ, Phys Dept, St Petersburg 198504, Russia.
    Henri, Pierre
    CNRS, LPC2E, F-45071 Orleans, France..
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Markidis, Stefano
    KTH Royal Inst Technol, S-10044 Stockholm, Sweden..
    Olshevsky, Vyacheslav
    Katholieke Univ Leuven, Ctr Math Plasma Astrophys CmPA, B-3001 Leuven, Belgium..
    Horányi, Mihály
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA.;NASA, SSERVI, Inst Modeling Plasma Atmospheres & Cosm Dus, Moffett Field, CA 94035 USA..
    Electron and Ion Dynamics of the Solar Wind Interaction with a Weakly Outgassing Comet2017In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 118, no 20, article id 205101Article in journal (Refereed)
    Abstract [en]

    Using a 3D fully kinetic approach, we disentangle and explain the ion and electron dynamics of the solar wind interaction with a weakly outgassing comet. We show that, to first order, the dynamical interaction is representative of a four-fluid coupled system. We self-consistently simulate and identify the origin of the warm and suprathermal electron distributions observed by ESA's Rosetta mission to comet 67P/Churyumov-Gerasimenko and conclude that a detailed kinetic treatment of the electron dynamics is critical to fully capture the complex physics of mass-loading plasmas.

  • 182.
    Deca, Jan
    et al.
    Katholieke Univ Leuven, Dept Math, Ctr Math Plasma Astrophys, Leuven, Belgium.;Univ Versailles St Quentin, Lab Atmospheres, Milieux, Observat Spati, Guyancourt, France.;Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA..
    Divin, Andrey
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. St Petersburg State Univ, Dept Phys, St Petersburg 199034, Russia..
    Lembege, Bertrand
    Univ Versailles St Quentin, Lab Atmospheres, Milieux, Observat Spati, Guyancourt, France..
    Horanyi, Mihaly
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80309 USA..
    Markidis, Stefano
    Royal Inst Technol, High Performance Comp & Visualizat, Stockholm, Sweden..
    Lapenta, Giovanni
    Katholieke Univ Leuven, Dept Math, Ctr Math Plasma Astrophys, Leuven, Belgium..
    General mechanism and dynamics of the solar wind interaction with lunar magnetic anomalies from 3-D particle-in-cell simulations2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 8, p. 6443-6463Article in journal (Refereed)
    Abstract [en]

    We present a general model of the solar wind interaction with a dipolar lunar crustal magnetic anomaly (LMA) using three-dimensional full-kinetic and electromagnetic simulations. We confirm that LMAs may indeed be strong enough to stand off the solar wind from directly impacting the lunar surface, forming a so-called minimagnetosphere, as suggested by spacecraft observations and theory. We show that the LMA configuration is driven by electron motion because its scale size is small with respect to the gyroradius of the solar wind ions. We identify a population of back-streaming ions, the deflection of magnetized electrons via the E x B drift motion, and the subsequent formation of a halo region of elevated density around the dipole source. Finally, it is shown that the presence and efficiency of the processes are heavily impacted by the upstream plasma conditions and, on their turn, influence the overall structure and evolution of the LMA system. Understanding the detailed physics of the solar wind interaction with LMAs, including magnetic shielding, particle dynamics and surface charging is vital to evaluate its implications for lunar exploration.

  • 183.
    Deca, Jan
    et al.
    Univ Colorado Boulder, Lab Atmospher & Space Phys, Boulder, CO USA; NASA SSERVI, Inst Modeling Plasma Atmospheres & Cosm Dust, Moffett Field, CA USA; Univ Versailles St Quentin, Lab Atmospheres Milieux Observat Spatiales, Guyancourt, France.
    Divin, Andrey
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. St Petersburg State Univ, Phys Dept, St Petersburg, Russia; Swedish Inst Space Phys, Uppsala, Sweden.
    Lue, Charles
    Univ Iowa, Dept Phys & Astron, Iowa City, IA USA; Swedish Inst Space Phys, Kiruna, Sweden.
    Ahmadi, Tara
    St Petersburg State Univ, Phys Dept, St Petersburg, Russia.
    Horanyi, Mihaly
    Univ Colorado Boulder, Lab Atmospher & Space Phys, Boulder, CO USA; NASA SSERVI, Inst Modeling Plasma Atmospheres & Cosm Dust, Moffett Field, CA USA.
    Reiner Gamma albedo features reproduced by modeling solar wind standoff2018In: Communications Physics, E-ISSN 2399-3650, Vol. 1, article id 12Article in journal (Refereed)
    Abstract [en]

    All lunar swirls are known to be co-located with crustal magnetic anomalies (LMAs). Not all LMAs can be associated with albedo markings, making swirls, and their possible connection with the former, an intriguing puzzle yet to be solved. By coupling fully kinetic simulations with a Surface Vector Mapping model, we show that solar wind standoff, an ion–electron kinetic interaction mechanism that locally prevents weathering by solar wind ions, reproduces the shape of the Reiner Gamma albedo pattern. Our method reveals why not every magnetic anomaly forms a distinct albedo marking. A qualitative match between optical remote observations and in situ particle measurements of the back-scattered ions is simultaneously achieved, demonstrating the importance of a kinetic approach to describe the solar wind interaction with LMAs. The anti-correlation between the predicted amount of surface weathering and the surface reflectance is strongest when evaluating the proton energy flux.

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  • 184.
    Deca, Jan
    et al.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.;NASA, Inst Modeling Plasma Atmospheres & Cosm Dust, SSERVI, Boulder, CO 80305 USA.;Univ Versailles St Quentin, Observat Spatiales, Lab Atmospheres, Milieux, Guyancourt, France..
    Divin, Andrey
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. St Petersburg State Univ, Dept Phys, St Petersburg 199034, Russia..
    Wang, Xu
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.;NASA, Inst Modeling Plasma Atmospheres & Cosm Dust, SSERVI, Boulder, CO 80305 USA..
    Lembege, Bertrand
    Univ Versailles St Quentin, Observat Spatiales, Lab Atmospheres, Milieux, Guyancourt, France..
    Markidis, Stefano
    KTH Royal Inst Technol, High Performance Comp & Visualizat, Stockholm, Sweden..
    Horanyi, Mihaly
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA.;NASA, Inst Modeling Plasma Atmospheres & Cosm Dust, SSERVI, Boulder, CO 80305 USA..
    Lapenta, Giovanni
    Katholieke Univ Leuven, Dept Math, Ctr Math Plasma Astrophys, Leuven, Belgium..
    Three-dimensional full-kinetic simulation of the solar wind interaction with a vertical dipolar lunarmagnetic anomaly2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 9, p. 4136-4144Article in journal (Refereed)
    Abstract [en]

    A detailed understanding of the solar wind interaction with lunar magnetic anomalies (LMAs) is essential to identify its implications for lunar exploration and to enhance our physical understanding of the particle dynamics in a magnetized plasma. We present the first three-dimensional full-kinetic electromagnetic simulation case study of the solar wind interaction with a vertical dipole, resembling a medium-size LMA. In contrast to a horizontal dipole, we show that a vertical dipole twists its field lines and cannot form a minimagnetosphere. Instead, it creates a ring-shaped weathering pattern and reflects up to 21% (four times more as compared to the horizontal case) of the incoming solar wind ions electrostatically through the normal electric field formed above the electron shielding region surrounding the cusp. This work delivers a vital piece to fully comprehend and interpret lunar observations, as we find the amount of reflected ions to be a tracer for the underlying field structure.

  • 185.
    Deca, Jan
    et al.
    Univ Colorado, LASP, Boulder, CO 80303 USA;NASA, Inst Modeling Plasma Atmospheres & Cosm Dust, SSERVI, Moffett Field, CA 94035 USA.
    Henri, Pierre
    CNRS, LPC2E, F-45071 Orleans, France;Univ Cote dAzur, Observ Cote dAzur, CNRS, Lab Lagrange, Nice, France.
    Divin, Andrey
    St Petersburg State Univ, Phys Dept, St Petersburg 198504, Russia.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Galand, Marina
    Imperial Coll London, Dept Phys, London SW7 2AZ, England.
    Beth, Arnaud
    Imperial Coll London, Dept Phys, London SW7 2AZ, England.
    Ostaszewski, Katharina
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys IGeP, D-38106 Braunschweig, Germany.
    Horanyi, Mihaly
    Univ Colorado, LASP, Boulder, CO 80303 USA;NASA, Inst Modeling Plasma Atmospheres & Cosm Dust, SSERVI, Moffett Field, CA 94035 USA;Univ Colorado, Dept Phys, Boulder, CO 80309 USA.
    Building a Weakly Outgassing Comet from a Generalized Ohm's Law2019In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 123, no 5, article id 055101Article in journal (Refereed)
    Abstract [en]

    When a weakly outgassing comet is sufficiently close to the Sun, the formation of an ionized coma results in solar wind mass loading and magnetic field draping around its nucleus. Using a 3D fully kinetic approach, we distill the components of a generalized Ohm's law and the effective electron equation of state directly from the self-consistently simulated electron dynamics and identify the driving physics in the various regions of the cometary plasma environment. Using the example of space plasmas, in particular multispecies cometary plasmas, we show how the description for the complex kinetic electron dynamics can be simplified through a simple effective closure, and identify where an isotropic single-electron fluid Ohm's law approximation can be used, and where it fails.

  • 186. Deng, X. H.
    et al.
    Zhou, M.
    Li, S. Y.
    Baumjohann, W.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Cornilleau, N.
    Santolik, O.
    Pontin, D. I.
    Reme, H.
    Lucek, E.
    Fazakerley, A. N.
    Decreau, P.
    Daly, P.
    Nakamura, R.
    Tang, R. X.
    Hu, Y. H.
    Pang, Y.
    Buechner, J.
    Zhao, H.
    Vaivads, Andris
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Pickett, J. S.
    Ng, C. S.
    Lin, X.
    Fu, S.
    Yuan, Z. G.
    Su, Z. W.
    Wang, J. F.
    Dynamics and waves near multiple magnetic null points in reconnection diffusion region2009In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, no 7, p. A07216-Article in journal (Refereed)
    Abstract [en]

    Identifying the magnetic structure in the region where the magnetic field lines break and how reconnection happens is crucial to improving our understanding of three-dimensional reconnection. Here we show the in situ observation of magnetic null structures in the diffusion region, the dynamics, and the associated waves. Possible spiral null pair has been identified near the diffusion region. There is a close relation among the null points, the bipolar signature of the Z component of the magnetic field, and enhancement of the flux of energetic electrons up to 100 keV. Near the null structures, whistler-mode waves were identified by both the polarity and the power law of the spectrum of electric and magnetic fields. It is found that the angle between the fans of the nulls is quite close to the theoretically estimated maximum value of the group-velocity cone angle for the whistler wave regime of reconnection.

  • 187.
    Desai, R. T.
    et al.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Coates, A. J.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Wellbrock, A.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Vuitton, V.
    Univ Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France..
    Crary, F. J.
    Univ Colorado, Lab Atmospher & Space Phys, Innovat Dr, Boulder, CO 80303 USA..
    Gonzalez-Caniulef, D.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England..
    Shebanits, Oleg
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Jones, G. H.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Lewis, G. R.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England..
    Waite, J. H.
    Southwest Res Inst SWRI, Space Sci & Engn Div, 6220 Culebra Rd, San Antonio, TX 78238 USA..
    Cordiner, M.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA..
    Taylor, S. A.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England.;UCL Birkbeck, Ctr Planetary Sci, Gower St, London WC1E 6BT, England..
    Kataria, D. O.
    Univ Coll London, Mullard Space Sci Lab, Holmbury RH5 6NT, Surrey, England..
    Wahlund, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Edberg, Niklas J. T.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sittler, E. C.
    NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA..
    Carbon Chain Anions and the Growth of Complex Organic Molecules in Titan's Ionosphere2017In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 844, no 2, article id L18Article in journal (Refereed)
    Abstract [en]

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

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  • 188.
    Dieval, C.
    et al.
    Univ Lancaster, Dept Phys, Lancaster, England.;Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Andrews, David J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Morgan, D. D.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    Brain, D. A.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Gurnett, D. A.
    Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USA..
    MARSIS remote sounding of localized density structures in the dayside Martian ionosphere: A study of controlling parameters2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 9, p. 8125-8145Article in journal (Refereed)
    Abstract [en]

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

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

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

  • 190.
    Dimmock, A. P.
    et al.
    Swedish Inst Space Phys IRF, Uppsala, Sweden..
    Khotyaintsev, Yu. V.
    Swedish Inst Space Phys IRF, Uppsala, Sweden..
    Lalti, Ahmad
    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. Swedish Inst Space Phys IRF, Uppsala, Sweden..
    Yordanova, E.
    Swedish Inst Space Phys IRF, Uppsala, Sweden..
    Edberg, N. J. T.
    Swedish Inst Space Phys IRF, Uppsala, Sweden..
    Steinvall, Konrad
    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. Swedish Inst Space Phys IRF, Uppsala, Sweden..
    Graham, D. B.
    Swedish Inst Space Phys IRF, Uppsala, Sweden..
    Hadid, L. Z.
    Univ Paris Saclay, Sorbonne Univ, Observ Paris, LPP,CNRS,Ecole Polytech, Paris, France..
    Allen, R. C.
    Johns Hopkins Appl Phys Lab, Laurel, MD 20723 USA..
    Vaivads, A.
    KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Div Space & Plasma Phys, S-11428 Stockholm, Sweden..
    Maksimovic, M.
    Univ Paris Diderot, Sorbonne Univ, Sorbonne Paris Cite, LESIA,Observ Paris,Univ PSL,CNRS, 5 Pl Jules Janssen, F-92195 Meudon, France..
    Bale, S. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA..
    Chust, T.
    Univ Paris Saclay, Sorbonne Univ, Observ Paris, LPP,CNRS,Ecole Polytech, Paris, France..
    Krasnoselskikh, V.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA.;CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France..
    Kretzschmar, M.
    CNRS, LPC2E, 3A Ave Rech Sci, Orleans, France.;Univ Orleans, Orleans, France..
    Lorfevre, E.
    CNES, 18 Ave Edouard Belin, F-31400 Toulouse, France..
    Plettemeier, D.
    Tech Univ Dresden, Helmholtz Str 10, D-01187 Dresden, Germany..
    Soucek, J.
    Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic..
    Steller, M.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Stverak, S.
    Czech Acad Sci, Inst Atmospher Phys, Prague, Czech Republic.;Czech Acad Sci, Astron Inst, Prague, Czech Republic..
    Travnicek, P.
    Czech Acad Sci, Astron Inst, Prague, Czech Republic..
    Vecchio, A.
    Univ Paris Diderot, Sorbonne Univ, Sorbonne Paris Cite, LESIA,Observ Paris,Univ PSL,CNRS, 5 Pl Jules Janssen, F-92195 Meudon, France.;Radboud Univ Nijmegen, Dept Astrophys, Radboud Radio Lab, Nijmegen, Netherlands..
    Horbury, T. S.
    Imperial Coll London, South Kensington Campus, London SW7 2AZ, England..
    O'Brien, H.
    Imperial Coll London, South Kensington Campus, London SW7 2AZ, England..
    Evans, V.
    Imperial Coll London, South Kensington Campus, London SW7 2AZ, England..
    Angelini, V.
    Imperial Coll London, South Kensington Campus, London SW7 2AZ, England..
    Analysis of multiscale structures at the quasi-perpendicular Venus bow shock Results from Solar Orbiter's first Venus flyby2022In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 660, article id A64Article in journal (Refereed)
    Abstract [en]

    Context. Solar Orbiter is a European Space Agency mission with a suite of in situ and remote sensing instruments to investigate the physical processes across the inner heliosphere. During the mission, the spacecraft is expected to perform multiple Venus gravity assist maneuvers while providing measurements of the Venusian plasma environment. The first of these occurred on 27 December 2020, in which the spacecraft measured the regions such as the distant and near Venus magnetotail, magnetosheath, and bow shock. Aims. This study aims to investigate the outbound Venus bow shock crossing measured by Solar Orbiter during the first flyby. We study the complex features of the bow shock traversal in which multiple large amplitude magnetic field and density structures were observed as well as higher frequency waves. Our aim is to understand the physical mechanisms responsible for these high amplitude structures, characterize the higher frequency waves, determine the source of the waves, and put these results into context with terrestrial bow shock observations. Methods. High cadence magnetic field, electric field, and electron density measurements were employed to characterize the properties of the large amplitude structures and identify the relevant physical process. Minimum variance analysis, theoretical shock descriptions, coherency analysis, and singular value decomposition were used to study the properties of the higher frequency waves to compare and identify the wave mode. Results. The non-planar features of the bow shock are consistent with shock rippling and/or large amplitude whistler waves. Higher frequency waves are identified as whistler-mode waves, but their properties across the shock imply they may be generated by electron beams and temperature anisotropies. Conclusions. The Venus bow shock at a moderately high Mach number (similar to 5) in the quasi-perpendicular regime exhibits complex features similar to the Earth's bow shock at comparable Mach numbers. The study highlights the need to be able to distinguish between large amplitude waves and spatial structures such as shock rippling. The simultaneous high frequency observations also demonstrate the complex nature of energy dissipation at the shock and the important question of understanding cross-scale coupling in these complex regions. These observations will be important to interpreting future planetary missions and additional gravity assist maneuvers.

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  • 191.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Alho, M.
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Kallio, Esa
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Pope, Simon Alexander
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    Zhang, Tielong
    Harbin Inst Technol, Shenzhen, Peoples R China; Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Kilpua, E.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Pulkkinen, Tuija I.
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Futaana, Y.
    Swedish Inst Space Phys, Kiruna, Sweden.
    Coates, Andrew J.
    UCL, Mullard Space Sci Lab, London, England.
    The Response of the Venusian Plasma Environment to the Passage of an ICME: Hybrid Simulation Results and Venus Express Observations2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 5, p. 3580-3601Article in journal (Refereed)
    Abstract [en]

    Owing to the heritage of previous missions such as the Pioneer Venus Orbiter and Venus Express, the typical global plasma environment of Venus is relatively well understood. On the other hand, this is not true for more extreme driving conditions such as during passages of interplanetary coronal mass ejections (ICMEs). One of the outstanding questions is how do ICMEs, either the ejecta or sheath portions, impact (1) the Venusian magnetic topology and (2) escape rates of planetary ions? One of the main issues encountered when addressing these problems is the difficulty of inferring global dynamics from single spacecraft obits; this is where the benefits of simulations become apparent. In the present study, we present a detailed case study of an ICME interaction with Venus on 5 November 2011 in which the magnetic barrier reached over 250 nT. We use both Venus Express observations and hybrid simulation runs to study the impact on the field draping pattern and the escape rates of planetary O+ ions. The simulation showed that the magnetic field line draping pattern around Venus during the ICME is similar to that during typical solar wind conditions and that O+ ion escape rates are increased by approximately 30% due to the ICME. Moreover, the atypically large magnetic barrier appears to manifest from a number of factors such as the flux pileup, dayside compression, and the driving time from the ICME ejecta.

  • 192.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Gedalin, M.
    Ben Gurion Univ Negev, Dept Phys, Beer Sheva, Israel..
    Lalti, Ahmad
    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.
    Trotta, D.
    Imperial Coll London, London, England..
    Khotyaintsev, Yuri V.
    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.
    Johlander, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division. Swedish Def Res Agcy, Stockholm, Sweden..
    Vainio, R.
    Univ Turku, Turku, Finland..
    Blanco-Cano, X.
    Univ Nacl Autonoma Mexico, Dept Ciencias Espaciales, Inst Geofis, Ciudad De Mexico, Mexico..
    Kajdic, P.
    Univ Nacl Autonoma Mexico, Dept Ciencias Espaciales, Inst Geofis, Ciudad De Mexico, Mexico..
    Owen, C. J.
    UCL, Mullard Space Sci Lab, London, England..
    Wimmer-Schweingruber, R. F.
    Univ Kiel, Inst Expt & Appl Phys, D-24118 Kiel, Germany..
    Backstreaming ions at a high Mach number interplanetary shock: Solar Orbiter measurements during the nominal mission phase2023In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 679, article id A106Article in journal (Refereed)
    Abstract [en]

    Context: Solar Orbiter, a mission developed by the European Space Agency, explores in situ plasma across the inner heliosphere while providing remote-sensing observations of the Sun. The mission aims to study the solar wind, but also transient structures such as interplanetary coronal mass ejections and stream interaction regions. These structures often contain a leading shock wave that can differ from other plasma shock waves, such as those around planets. Importantly, the Mach number of these interplanetary shocks is typically low (1-3) compared to planetary bow shocks and most astrophysical shocks. However, our shock survey revealed that on 30 October 2021, Solar Orbiter measured a shock with an Alfven Mach number above 6, which can be considered high in this context.

    Aims: Our study examines particle observations for the 30 October 2021 shock. The particles provide clear evidence of ion reflection up to several minutes upstream of the shock. Additionally, the magnetic and electric field observations contain complex electromagnetic structures near the shock, and we aim to investigate how they are connected to ion dynamics. The main goal of this study is to advance our understanding of the complex coupling between particles and the shock structure in high Mach number regimes of interplanetary shocks.

    Methods: We used observations of magnetic and electric fields, probe-spacecraft potential, and thermal and energetic particles to characterize the structure of the shock front and particle dynamics. Furthermore, ion velocity distribution functions were used to study reflected ions and their coupling to the shock. To determine shock parameters and study waves, we used several methods, including cold plasma theory, singular-value decomposition, minimum variance analysis, and shock Rankine-Hugoniot relations. To support the analysis and interpretation of the experimental data, test-particle analysis, and hybrid particle in-cell simulations were used.

    Results: The ion velocity distribution functions show clear evidence of particle reflection in the form of backstreaming ions several minutes upstream. The shock structure has complex features at the ramp and whistler precursors. The backstreaming ions may be modulated by the complex shock structure, and the whistler waves are likely driven by gyrating ions in the foot. Supra-thermal ions up to 20 keV were observed, but shock-accelerated particles with energies above this were not.

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  • 193.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Hietala, H.
    Imperial Coll London, Blackett Lab, London, England.;Univ Turku, Dept Phys & Astron, Turku, Finland.;Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Zou, Y.
    Univ Alabama, Dept Space Sci, Huntsville, AL 35899 USA..
    Compiling Magnetosheath Statistical Data Sets Under Specific Solar Wind Conditions: Lessons Learnt From the Dayside Kinetic Southward IMF GEM Challenge2020In: Earth and Space Science, E-ISSN 2333-5084, Vol. 7, no 6, article id UNSP e2020EA001095Article in journal (Refereed)
    Abstract [en]

    The Geospace Environmental Modelling (GEM) community offers a framework for collaborations between modelers, observers, and theoreticians in the form of regular challenges. In many cases, these challenges involve model-data comparisons to provide wider context to observations or validate model results. To perform meaningful comparisons, a statistical approach is often adopted, which requires the extraction of a large number of measurements from a specific region. However, in complex regions such as the magnetosheath, compiling these data can be difficult. Here, we provide the statistical context of compiling statistical data for the southward IMF GEM challenge initiated by the "Dayside Kinetic Processes in Global Solar Wind-Magnetosphere Interaction" focus group. It is shown that matching very specific upstream conditions can severely impact the statistical data if limits are imposed on several solar wind parameters. We suggest that future studies that wish to compare simulations and/or single events to statistical data should carefully consider at an early stage the availability of data in context with the upstream criteria. We also demonstrate the importance of how specific IMF conditions are defined, the chosen spacecraft, the region of interest, and how regions are identified automatically. The lessons learnt in this study are of wide context to many future studies as well as GEM challenges. The results also highlight the issue where a global statistical perspective has to be balanced with its relevance to more-extreme, less-frequent individual events, which is typically the case in the field of space weather.

  • 194.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Rosenqvist, L.
    Swedish Def Res Agcy, Stockholm, Sweden.
    Hall, J-O
    Swedish Def Res Agcy, Stockholm, Sweden;Swedish Nucl Fuel & Waste Management Co, Solna, Sweden.
    Viljanen, A.
    Finnish Meteorol Inst, Helsinki, Finland.
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Honkonen, I
    Finnish Meteorol Inst, Helsinki, Finland.
    André, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Sjoberg, E. C.
    Swedish Inst Space Phys, Kiruna, Sweden.
    The GIC and Geomagnetic Response Over Fennoscandia to the 7-8 September 2017 Geomagnetic Storm2019In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 17, no 7, p. 989-1010Article in journal (Refereed)
    Abstract [en]

    Between 7 and 8 September 2017, Earth experienced extreme space weather events. We have combined measurements made by the IMAGE magnetometer array, ionospheric equivalent currents, geomagnetically induced current (GIC) recordings in the Finnish natural gas pipeline, and multiple ground conductivity models to study the Fennoscandia ground effects. This unique analysis has revealed multiple interesting physical and technical insights. We show that although the 7-8 September event was significant by global indices (Dst similar to 150 nT), it produced an unexpectedly large peak GIC. It is intriguing that our peak GIC did not occur during the intervals of largest geomagnetic depressions, nor was there any clear upstream trigger. Another important insight into this event is that unusually large and rare GIC amplitudes (>10 A) occurred in multiple Magnetic Local Time (MLT) sectors and could be associated with westward and eastward electrojets. We were also successfully able to model the geoelectric field and GIC using multiple models, thus providing a further important validation of these models for an extreme event. A key result from our multiple conductivity model comparison was the good agreement between the temporal features of 1-D and 3-D model results. This provides an important justification for past and future uses of 1-D models at Mantsala which is highly relevant to additional uses of this data set. Although the temporal agreement (after scaling) was good, we found a large (factor of 4) difference in the amplitudes between local and global ground models due to the difference in model conductivities. Thus, going forward, obtaining accurate ground conductivity values are key for GIC modeling.

  • 195.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Rosenqvist, L.
    Swedish Res Def Agcy, Stockholm, Sweden..
    Welling, D. T.
    Univ Texas Arlington, Dept Phys, POB 19059, Arlington, TX 76019 USA..
    Viljanen, A.
    Finnish Meteorol Inst, Helsinki, Finland..
    Honkonen, I.
    Finnish Meteorol Inst, Helsinki, Finland..
    Boynton, R. J.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    On the Regional Variability ofdB/dtand Its Significance to GIC2020In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 18, no 8, article id e2020SW002497Article in journal (Refereed)
    Abstract [en]

    Faraday's law of induction is responsible for setting up a geoelectric field due to the variations in the geomagnetic field caused by ionospheric currents. This drives geomagnetically induced currents (GICs) which flow in large ground-based technological infrastructure such as high-voltage power lines. The geoelectric field is often a localized phenomenon exhibiting significant variations over spatial scales of only hundreds of kilometers. This is due to the complex spatiotemporal behavior of electrical currents flowing in the ionosphere and/or large gradients in the ground conductivity due to highly structured local geological properties. Over some regions, and during large storms, both of these effects become significant. In this study, we quantify the regional variability ofdB/dtusing closely placed IMAGE stations in northern Fennoscandia. The dependency between regional variability, solar wind conditions, and geomagnetic indices are also investigated. Finally, we assess the significance of spatial geomagnetic variations to modeling GICs across a transmission line. Key results from this study are as follows: (1) Regional geomagnetic disturbances are important in modeling GIC during strong storms; (2)dB/dtcan vary by several times up to a factor of three compared to the spatial average; (3)dB/dtand its regional variation is coupled to the energy deposited into the magnetosphere; and (4) regional variability can be more accurately captured and predicted from a local index as opposed to a global one. These results demonstrate the need for denser magnetometer networks at high latitudes where transmission lines extending hundreds of kilometers are present.

  • 196.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Russell, Christopher T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA.
    Sagdeev, Roald Z.
    Univ Maryland, Dept Phys, College Pk, MD 20742 USA.
    Krasnoselskikh, Vladimir
    Univ Orleans, CNRS, LPC2E, Orleans, France;Univ Calif Berkeley, Space Sci Lab, 7 Gauss Way, Berkeley, CA 94720 USA.
    Walker, Simon N.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    Carr, Christopher
    Imperial Coll London, London SW7 2AZ, England.
    Dandouras, Iannis
    Univ Toulouse, IRAP, CNRS, UPS,CNES, Toulouse, France.
    Escoubet, C. Philippe
    European Space Agcy, European Space Res & Technol Ctr ESA ESTEC, Noordwijk, Netherlands.
    Ganushkina, Natalia
    Finnish Meteorol Inst, Helsinki, Finland;Univ Michigan, Ann Arbor, MI 48109 USA.
    Gedalin, Michael
    Ben Gurion Univ Negev, Dept Phys, Beer Sheva, Israel.
    Khotyaintsev, Yuri V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Aryan, Homayon
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England;NASA Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.
    Pulkkinen, Tuija, I
    Univ Michigan, Ann Arbor, MI 48109 USA;Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Balikhin, Michael A.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    Direct evidence of nonstationary collisionless shocks in space plasmas2019In: Science Advances, E-ISSN 2375-2548, Vol. 5, no 2, article id eaau9926Article in journal (Refereed)
    Abstract [en]

    Collisionless shocks are ubiquitous throughout the universe: around stars, supernova remnants, active galactic nuclei, binary systems, comets, and planets. Key information is carried by electromagnetic emissions from particles accelerated by high Mach number collisionless shocks. These shocks are intrinsically nonstationary, and the characteristic physical scales responsible for particle acceleration remain unknown. Quantifying these scales is crucial, as it affects the fundamental process of redistributing upstream plasma kinetic energy into other degrees of freedom-particularly electron thermalization. Direct in situ measurements of nonstationary shock dynamics have not been reported. Thus, the model that best describes this process has remained unknown. Here, we present direct evidence demonstrating that the transition to nonstationarity is associated with electron-scale field structures inside the shock ramp.

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  • 197.
    Dimmock, Andrew P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Welling, D. T.
    Univ Texas Arlington, Dept Phys, POB 19059, Arlington, TX 76019 USA..
    Rosenqvist, L.
    Swedish Def Res Agcy, Stockholm, Sweden..
    Forsyth, C.
    UCL Mullard Space Sci Lab, Dorking, Surrey, England..
    Freeman, M. P.
    British Antarctic Survey, Cambridge, England..
    Rae, I. J.
    UCL Mullard Space Sci Lab, Dorking, Surrey, England.;Northumbria Univ, Newcastle Upon Tyne, Tyne & Wear, England..
    Viljanen, A.
    Finnish Meteorol Inst, Helsinki, Finland..
    Vandegriff, E.
    Univ Texas Arlington, Dept Phys, POB 19059, Arlington, TX 76019 USA..
    Boynton, R. J.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England..
    Balikhin, M. A.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England..
    Yordanova, Emiliya
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Modeling the Geomagnetic Response to the September 2017 Space Weather Event Over Fennoscandia Using the Space Weather Modeling Framework: Studying the Impacts of Spatial Resolution2021In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 19, no 5, article id e2020SW002683Article in journal (Refereed)
    Abstract [en]

    We must be able to predict and mitigate against geomagnetically induced current (GIC) effects to minimize socio-economic impacts. This study employs the space weather modeling framework (SWMF) to model the geomagnetic response over Fennoscandia to the September 7-8, 2017 event. Of key importance to this study is the effects of spatial resolution in terms of regional forecasts and improved GIC modeling results. Therefore, we ran the model at comparatively low, medium, and high spatial resolutions. The virtual magnetometers from each model run are compared with observations from the IMAGE magnetometer network across various latitudes and over regional-scales. The virtual magnetometer data from the SWMF are coupled with a local ground conductivity model which is used to calculate the geoelectric field and estimate GICs in a Finnish natural gas pipeline. This investigation has lead to several important results in which higher resolution yielded: (1) more realistic amplitudes and timings of GICs, (2) higher amplitude geomagnetic disturbances across latitudes, and (3) increased regional variations in terms of differences between stations. Despite this, substorms remain a significant challenge to surface magnetic field prediction from global magnetohydrodynamic modeling. For example, in the presence of multiple large substorms, the associated large-amplitude depressions were not captured, which caused the largest model-data deviations. The results from this work are of key importance to both modelers and space weather operators. Particularly when the goal is to obtain improved regional forecasts of geomagnetic disturbances and/or more realistic estimates of the geoelectric field.

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  • 198.
    Dimmock, Andrew P.
    et al.
    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.
    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.
    Blanco-Cano, X.
    Univ Nacl Autonoma Mexico, Inst Geofis, Dept Ciencias Espaciales, Ciudad Univ, Ciudad De Mexico, Mexico..
    KajdiC, P.
    Univ Nacl Autonoma Mexico, Inst Geofis, Dept Ciencias Espaciales, Ciudad Univ, Ciudad De Mexico, Mexico..
    Karlsson, T.
    KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Div Space & Plasma Phys, Stockholm, Sweden..
    Fedorov, A.
    IRAP UPS CNRS, Toulouse, France..
    Owen, C. J.
    UCL, Mullard Space Sci Lab, London, England..
    Werner, Elisabeth
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Johlander, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Mirror Mode Storms Observed by Solar Orbiter2022In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 127, no 11, article id e2022JA030754Article in journal (Refereed)
    Abstract [en]

    Mirror modes (MMs) are ubiquitous in space plasma and grow from pressure anisotropy. Together with other instabilities, they play a fundamental role in constraining the free energy contained in the plasma. This study focuses on MMs observed in the solar wind by Solar Orbiter (SolO) for heliocentric distances between 0.5 and 1 AU. Typically, MMs have timescales from several to tens of seconds and are considered quasi-MHD structures. In the solar wind, they also generally appear as isolated structures. However, in certain conditions, prolonged and bursty trains of higher frequency MMs are measured, which have been labeled previously as MM storms. At present, only a handful of existing studies have focused on MM storms, meaning that many open questions remain. In this study, SolO has been used to investigate several key aspects of MM storms: their dependence on heliocentric distance, association with local plasma properties, temporal/spatial scale, amplitude, and connections with larger-scale solar wind transients. The main results are that MM storms often approach local ion scales and can no longer be treated as quasi-magnetohydrodynamic, thus breaking the commonly used long-wavelength assumption. They are typically observed close to current sheets and downstream of interplanetary shocks. The events were observed during slow solar wind speeds and there was a tendency for higher occurrence closer to the Sun. The occurrence is low, so they do not play a fundamental role in regulating ambient solar wind but may play a larger role inside transients.

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  • 199.
    Divin, A.
    et al.
    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.
    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.
    Markidis, S.
    Lapenta, G.
    Evolution of the lower hybrid drift instability at reconnection jet front2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 4, p. 2675-2690Article in journal (Refereed)
    Abstract [en]

    We investigate current-driven modes developing at jet fronts during collisionless reconnection. Initial evolution of the reconnection is simulated using conventional 2-D setup starting from the Harris equilibrium. Three-dimensional PIC calculations are implemented at later stages, when fronts are fully formed. Intense currents and enhanced wave activity are generated at the fronts because of the interaction of the fast flow plasma and denser ambient current sheet plasma. The study reveals that the lower hybrid drift instability develops quickly in the 3-D simulation. The instability produces strong localized perpendicular electric fields, which are several times larger than the convective electric field at the front, in agreement with Time History of Events and Macroscale Interactions during Substorms observations. The instability generates waves, which escape the front edge and propagate into the undisturbed plasma ahead of the front. The parallel electron pressure is substantially larger in the 3-D simulation compared to that of the 2-D. In a time similar to Omega(-1)(ci), the instability forms a layer, which contains a mixture of the jet plasma and current sheet plasma. The results confirm that the lower hybrid drift instability is important for the front evolution and electron energization.

  • 200.
    Divin, Andrey
    et al.
    St Petersburg State Univ, Ulianovskaya 1, St Petersburg 198504, Russia.
    Deca, Jan
    Univ Colorado, LASP, Boulder, CO 80303 USA;NASA, Inst Modeling Plasma Atmospheres & Cosm Dust, SSERVI, Moffett Field, CA 94035 USA.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Swedish Institute of Space Physics, Uppsala Division.
    Henri, Pierre
    CNRS, LPC2E, 3 Ave Rech Sci, F-45071 Orleans, France;UCA, CNRS, OCA, Lab Lagrange, Nice, France.
    Lapenta, Giovanni
    Katholieke Univ Leuven, CmPA, Dept Math, Celestijnenlaan 200B,Bus 2400, B-3001 Leuven, Belgium.
    Olshevsky, Vyacheslav
    KTH Royal Inst Technol, SE-10044 Stockholm, Sweden.
    Markidis, Stefano
    KTH Royal Inst Technol, SE-10044 Stockholm, Sweden.
    A Fully Kinetic Perspective of Electron Acceleration around a Weakly Outgassing Comet2020In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 889, no 2, article id L33Article in journal (Refereed)
    Abstract [en]

    The cometary mission Rosetta has shown the presence of higher-than-expected suprathermal electron fluxes. In this study, using 3D fully kinetic electromagnetic simulations of the interaction of the solar wind with a comet, we constrain the kinetic mechanism that is responsible for the bulk electron energization that creates the suprathermal distribution from the warm background of solar wind electrons. We identify and characterize the magnetic field-aligned ambipolar electric field that ensures quasi-neutrality and traps warm electrons. Solar wind electrons are accelerated to energies as high as 50-70 eV close to the comet nucleus without the need for wave-particle or turbulent heating mechanisms. We find that the accelerating potential controls the parallel electron temperature, total density, and (to a lesser degree) the perpendicular electron temperature and the magnetic field magnitude. Our self-consistent approach enables us to better understand the underlying plasma processes that govern the near-comet plasma environment.

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