Energetic particle fluxes onto Callisto's atmosphere

Jupiter’s moon Callisto is exposed to a highly dynamic magnetospheric environment. During a full synodic period, properties of the local magnetospheric field and thermal plasma environment change by an order of magnitude, and Callisto’s resulting interaction with the ambient plasma displays a strong variability.

In this study, we combine results from the AIKEF hybrid and GENTOo test-particle models to constrain the variability of energetic particle dynamics and quantify their flux onto the top of Callisto’s atmosphere during a synodic period. For three positions of Callisto with respect to the center of the Jovian current sheet (at maximum distance above, maximum distance below, and embedded within), we model the interaction between Callisto’s atmosphere/ionosphere, its induced field, and ambient magnetospheric plasma environment, and we trace energetic ions (hydrogen, oxygen, and sulfur) and electrons through the perturbed electromagnetic fields. Our findings highlight the important role that Callisto's interaction with the low energy magnetospheric plasma and signatures associated with the moon’s induced field have on shaping the dynamics and flux patterns of the high-energy particles, which may play a role in the asymmetric ionization of, and energy deposition into, Callisto's neutral atmosphere.