First 3D test particle model of Ganymede's ionosphere

Carnielli, Gianluca; Galand, M.; Leblanc, François; Leclercq, Ludivine; Modolo, Ronan; Beth, Arnaud; Huybrighs, Hans; Jia, Xianzhe

doi:10.1016/j.icarus.2019.04.016

Cited by 25 publications

(60 citation statements)

References 55 publications

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“…The presence of these bands with enhanced electron flux likely generate an asymmetric weathering pattern of Ganymede's high‐latitude surface and may partially contribute to the nonuniform ionization of its atmosphere (albeit to a lesser degree than by electrons with energies E ≪ 4.5 keV; cf. Carnielli et al, 2019). Hence in summary, Ganymede's interaction with the ambient plasma and the rapid bounce times of electrons near Ganymede (e.g., Figure 5) both contribute to the generation of these high‐latitude “bands” of enhanced electron flux along Ganymede's high‐latitude, trailing hemisphere surface.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, particle precipitation onto these regions helps sustain Ganymede's tenuous exosphere via sputtering of its surface ices (e.g., Carnielli et al, 2020; Ip et al, 1997; Paranicas et al, 1999; Plainaki et al, 2015; Poppe et al, 2018). The energetic particles may also partially ionize the resulting neutral exosphere, although to a much lesser degree than the thermal plasma at lower energies (see, e.g., Carnielli et al, 2019; Erdman & Zipf, 1986; Saur et al, 1998; Wells et al, 1971).…”

Section: Introductionmentioning

confidence: 99%

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Variability in the Energetic Electron Bombardment of Ganymede

et al. 2020

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This study examines the bombardment of energetic magnetospheric electrons onto Ganymede as a function of Jovian magnetic latitude. We use the output from a three-dimensional, hybrid model to constrain features of the electromagnetic environment during the G1, G8, and G28 Galileo encounters when Ganymede was located far above, within, or far below Jupiter's magnetospheric current sheet, respectively. To quantify electron fluxes, we use a test-particle model and trace relativistic electrons at discrete energies between 4.5 keV ≤E ≤ 100 MeV while exposed to these fields. For each location with respect to Jupiter's current sheet, electrons of all energies bombard Ganymede's poles with average number and energy fluxes of 1 • 10 8 cm −2 s −1 and 3 • 10 9 keV cm −2 s −1 , respectively. However, bombardment is locally inhomogeneous: poleward of the open-closed field line boundary, fluxes are enhanced in the trailing hemisphere but reduced in the leading hemisphere. When embedded within the Jovian current sheet, closed field lines of Ganymede's minimagnetosphere shield electrons below 40 MeV from accessing the equator. Above these energies, equatorial fluxes are longitudinally inhomogeneous between the sub-Jovian and anti-Jovian hemispheres, but the averaged number flux (4 • 10 3 cm −2 s −1) is comparable to the flux deposited here by each of the dominant energetic ion species near Ganymede. When located outside of the Jovian current sheet, electrons below 100 keV enter Ganymede's minimagnetosphere via the downstream reconnection region and bombard the leading apex, while electrons of all energies are shielded from the trailing apex. Averaged over a full synodic rotation period of Jupiter, the energetic electron flux pattern agrees well with brightness features observed across Ganymede's polar and equatorial surface.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Variability in the Energetic Electron Bombardment of Ganymede

et al. 2020

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“…Recently, Carnielli et al. (2019, 2020) used a test particle Monte Carlo approach to build an ionosphere model for Ganymede that provides the spatial distribution of multiple ion species originating from Ganymede's ionosphere. The magnetosphere models presented here used a relatively simplified approach to treating the ionosphere in that uniform, fixed plasma density and temperature are prescribed at the simulation boundary near Ganymede's surface (Zhou et al., 2019).…”

Section: Discussionmentioning

confidence: 99%

Reconnection‐Driven Dynamics at Ganymede's Upstream Magnetosphere: 3‐D Global Hall MHD and MHD‐EPIC Simulations

et al. 2020

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The largest moon in the solar system, Ganymede, is the only moon known to possess a strong intrinsic magnetic field and a corresponding magnetosphere. Using the latest version of Space Weather Modeling Framework (SWMF), we study the upstream plasma interactions and dynamics in this sub‐Alfvénic system. Results from the Hall magnetohydrodynamics (MHD) and the coupled MHD with embedded particle‐in‐cell (MHD‐EPIC) models are compared. We find that under steady upstream conditions, magnetopause reconnection occurs in a nonsteady manner, and the energy partition between electrons and ions is different in the two models. Flux ropes of Ganymede's radius in length form on the magnetopause at a rate about 3 min and create spatiotemporal variations in plasma and field properties. Upon reaching proper grid resolutions, the MHD‐EPIC model can resolve both electron and ion kinetics at the magnetopause and show localized nongyrotropic behavior inside the diffusion region. The estimated global reconnection rate from the models is about 80 kV with 60% efficiency, and there is weak evidence of ∼1 min periodicity in the temporal variations due to the dynamic reconnection process.

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“…In this work we investigate the cause of the depletions during E26 by simulating the flux of energetic protons using a Monte Carlo particle backtracing method. Note that we refer to any kind of flux dropout as “depletion,” be it due to surface impact, charge exchange, or Galileo encountering a “forbidden region.” Particle tracing studies have been conducted at various moons, for example, at Jupiter's moons Europa (Breer et al, ; Cassidy et al, ), Ganymede (Carnielli et al, ), and Callisto (Liuzzo et al, ), at Titan (Regoli et al, ), at Earth's Moon using backtracing (Futaana et al, ), or at Mars and Phobos (Curry et al, ; Futaana et al, ). Ion depletions have been investigated using particle tracing, for example, at the Jovian moon Io and Ganymede (Poppe et al, ; Selesnick & Cohen, ) and Saturnian moons Dione, Rhea, and Titan (Kotova et al, ; Wulms et al, ).…”

Section: Introductionmentioning

confidence: 99%

An Active Plume Eruption on Europa During Galileo Flyby E26 as Indicated by Energetic Proton Depletions

Huybrighs

Roussos

Blöcker

et al. 2020

Geophysical Research Letters

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Strong depletions of energetic protons (115-244 keV) were observed during Galileo flyby E26of Europa. We simulate the flux of energetic protons using a Monte Carlo particle backtracing code and show that energetic proton depletions during E26 are reproduced by taking into account the perturbations of the electromagnetic fields calculated by magnetohydrodynamic (MHD) simulations and charge exchange with a global atmosphere and plume. A depletion feature occurring shortly after closest approach is driven by plume associated charge exchange, or a combination with plume associated field perturbations. We therefore conclude, with a new method and independent data set, that Galileo could have encountered a plume during E26. Plain Language SummaryWe investigate why (normally abundant) fast protons were disappearing during Europa flyby E26 by Galileo. We do this by simulating the proton motion. In some cases we detect few protons because Europa is blocking the field of view. What is new here is that part of the decrease can be explained by charge exchange, a process whereby the protons are removed after they lose their electrical charge in Europa's thin atmosphere. Furthermore, we see that there is a special decrease, which can be explained by an erupting plume of water vapor, thereby providing additional evidence for an active plume during Galileo flyby E26.

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First 3D test particle model of Ganymede's ionosphere

Cited by 25 publications

References 55 publications

Variability in the Energetic Electron Bombardment of Ganymede

Variability in the Energetic Electron Bombardment of Ganymede

Reconnection‐Driven Dynamics at Ganymede's Upstream Magnetosphere: 3‐D Global Hall MHD and MHD‐EPIC Simulations

An Active Plume Eruption on Europa During Galileo Flyby E26 as Indicated by Energetic Proton Depletions

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