Kinetic Simulations of the Jovian Energetic Ion Circulation around Ganymede

Abstract

The temporal and spatial variability of the radiation environment around Ganymede has a direct impact on the moon's exosphere, which links Jupiter's magnetosphere with the satellite's icy surface. The dynamics of the entry and circulation inside Ganymede's magnetosphere of the Jovian energetic ions, as well as the morphology of their precipitation on the moon's surface, determine the variability of the sputtered-water release. For this reason, the so-called planetary space weather conditions around Ganymede can also have a long-term impact on the weathering history of the moon's surface. In this work, we simulate the Jovian energetic ion precipitation to Ganymede's surface for different relative configurations between the moon's magnetic field and Jupiter's plasma sheet using a single-particle Monte Carlo model driven by the electromagnetic fields from a global MHD model. In particular, we study three science cases characterized by conditions similar to those encountered during the NASA Galileo G2, G8, and G28 flybys of Ganymede (i.e., when the moon was above, inside, and below the center of Jupiter's plasma sheet). We discuss the differences between the various surface precipitation patterns and the implications in the water sputtering rate. The results of this preliminary analysis are relevant to ESA's JUICE mission and in particular to the planning and optimization of future observation strategies for studying Ganymede's environment.