Energetic electron dynamics near Callisto.

We examine the dynamics of energetic magnetospheric electrons exposed to the highly perturbed and asymmetric plasma environment of Jupiter's moon Callisto. The interaction of the (nearly) corotating magnetospheric plasma with Callisto's ionosphere and induced dipole locally generates intense electromagnetic pileup and draping signatures which vary as a function of the moon's distance to the center of Jupiter's magnetospheric current sheet. In our study, these field perturbations are represented using output from the AIKEF hybrid (kinetic ions, fluid electrons) model of Callisto's interaction with the corotating plasma. In order to constrain the influence of Callisto's variable electromagnetic environment on the dynamics of energetic electrons, we trace the trajectories of more than 6.7 million test particles as they travel through a distinct configuration of the locally perturbed fields. We present spatially resolved maps that display the accessibility of Callisto to electrons at energies E between 10 1 keV ≤ E ≤ 10 5 keV for multiple sets of these perturbed fields, corresponding to select distances of the moon to the center of the Jovian current sheet. The electromagnetic field perturbations near Callisto play a crucial role in generating inhomogeneous precipitation of energetic electrons onto the top of the moon's atmosphere. In particular, Callisto's Jupiter-facing and Jupiter-averted hemispheres are partially protected from energetic electron precipitation: when located far above or below the center of Jupiter's current sheet, Callisto's induced dipole shields the apices of these hemispheres, whereas near the center of the sheet, strong field line draping protects these regions. In contrast to this, the apex of Callisto's trailing hemisphere is exposed to intense energetic electron precipitation at any distance to the center of the Jovian current sheet. We also present maps of energetic electron accessibility during the Galileo C3, C9, and C10 flybys, and calculate the intensity of energetic electron flux onto multiple locations at the top of Callisto's atmosphere. These non-uniform electron fluxes likely cause inhomogeneous ionization of Callisto's atmosphere and may even contribute to irregular erosion of the surface. This paper is a companion to Liuzzo et al. (2019), who studied the dynamics of energetic ions near Callisto. • Callisto's perturbed electromagnetic environment strongly affects energetic electron dynamics. • Induced fields and Alfvén wings partially shield Callisto from impinging magnetospheric electrons. • Energetic electron precipitation onto Callisto's atmosphere is highly inhomogeneous. • Electrons may leave Callisto's local environment, bounce, and then return, causing asymmetric precipitation patterns. [ABSTRACT FROM AUTHOR]