Acceleration of Energetic Electrons in Jovian Middle Magnetosphere by Whistler-Mode Waves

Abstract

An abundant multi-MeV electron population beyond the orbit of Io is required to explain the intense inner radiation belt (electrons $>50$ MeV) at Jupiter and its synchrotron radiation. In order to better understand the synergistic effect of radial transport and local wave-particle interactions driven by whistler-mode waves on the formation of Jupiter's radiation belt, we perform 3-D Fokker-Planck simulations for Jovian energetic electrons with the Versatile Electron Radiation Belt code. An empirical model of Jovian whistler-mode waves updated with measurements from the Juno extended mission is used to quantify the local acceleration and pitch angle scattering. Resonant cyclotron acceleration by whistler-mode waves leads to significant enhancement in the intensity of electrons above 1 MeV in the middle magnetosphere. Radial diffusion is capable of transporting MeV electrons accelerated by outer-belt whistler-mode waves into the region, where they are further accelerated adiabatically to energies of about 10 MeV.