Energetic Proton Distributions in the Inner and Middle Magnetosphere of Jupiter Using Juno Observations

Abstract

Jupiter is known to have a complex magnetosphere containing energetic (above 10s of keV) electrons, protons, and heavy ions. However, a global distribution of these energetic particles is not fully understood before the era of the polar-orbiting Juno mission. In this study, we focus on the energetic proton distribution at M < 50 by taking advantage of Juno's measurement covering various magnetic latitudes and M-shells, and find that energetic proton fluxes are higher off-equator than that near the equator at M > ∼20, and become comparable or lower at high latitudes than those near the equator at low M-shells. Pitch angle distributions of energetic protons are field-aligned, isotropic, and weak pancake-like from high to low M-shells. Proton phase space density shows a weak M-shell dependence at M > 30 and a large positive slope at M < 30, suggesting their potential source and loss processes.