The Jovian Energetic Ion Environment of Ganymede: Planetary Space Weather Considerations in View of the JUICE Mission

Determining the properties of radiation environments inside planetary magnetospheres is one of the key challenges of planetary space weather science. In this work, we expand our recent simulations of the Jovian energetic ion precipitation to Ganymede’s surface to deduce ion circulation patterns at the altitude of ∼500 km. We apply a single-particle Monte Carlo model to obtain 3D distribution maps of the H+, O++, and S+++ populations at the altitude of ∼500 km. We perform these simulations for three distinct configurations between Ganymede’s magnetic field and Jupiter’s plasma sheet, characterized by magnetic and electric field conditions similar to those during the NASA Galileo G2, G8, and G28 flybys (i.e., when the moon was above, inside, and below the center of Jupiter’s plasma sheet). Our results provide a reference frame for future studies of planetary space weather phenomena in the near-Ganymede region. For ions with energies up to some tens of kiloelectronvolts, we find an increased and spatially extended flow in the anti-Jupiter low-latitude and equatorial regions above Ganymede’s leading hemisphere. Our results also show that the ion flux incident at 500 km altitude is not a good approximation of the surface’s precipitating flux. To study, therefore, Ganymede’s surface erosion processes it may be best to consider also low-altitude orbits as part of future space missions. This study is relevant to the ESA JUpiter ICy moons Explorer mission, which will allow a detailed investigation of the Ganymede environment and its implications on the moon’s surface evolution.