Variability in the energetic electron bombardment of Ganymede
- 1Space Sciences Laboratory, University of California, Berkeley, United States of America
- 2The Johns Hopkins Univeristy Applied Physics Laboratory, Laurel, Maryland, United States of America
- 3Swedish Institute of Space Physics, Kiruna, Sweden
- 4Department of Physics, Umeå University, Umeå, Sweden
- 5School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, United States of America
This study examines the bombardment of energetic magnetospheric electrons onto Ganymede as a function of Jovian magnetic latitude. We use the output from a hybrid model to constrain features of the electromagnetic environment during the G1, G8, and G28 Galileo encounters when Ganymede was far above, within, or far below Jupiter's magnetospheric current sheet, respectively. To quantify electron fluxes, we use a test-particle model and trace 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 1·108 cm-2 s-1 and 3·109 keV cm-2 s-1, respectively. However, precipitation is inhomogeneous: poleward of the open-closed field line boundary, fluxes are enhanced in the trailing (but reduced in the leading) hemisphere. Within the Jovian current sheet, closed field lines of Ganymede's mini-magnetosphere shield electrons below 40 MeV from accessing the equator. Above these energies, equatorial fluxes are longitudinally inhomogeneous between the sub- and anti-Jovian hemispheres, but the averaged number flux (4·103 cm-2 s-1) is comparable to the flux deposited by each of the dominant energetic ion species near Ganymede. When outside of the Jovian current sheet, electrons below 100 keV enter Ganymede's mini-magnetosphere via the downstream reconnection region and bombard the leading apex, while electrons of all energies are shielded from the trailing apex. Averaged over a synodic rotation, electron flux patterns agree with brightness features observed across Ganymede's polar and equatorial surface.
How to cite: Liuzzo, L., Poppe, A., Paranicas, C., Nénon, Q., Fatemi, S., and Simon, S.: Variability in the energetic electron bombardment of Ganymede, Europlanet Science Congress 2020, online, 21 Sep–9 Oct 2020, EPSC2020-30, https://doi.org/10.5194/epsc2020-30, 2020.