Importance of electron distribution profiles to chorus wave driven evolution of Jovian radiation belt electrons

Abstract

Wave‐particle interactions triggered by whistler‐mode chorus waves are an important contributor to the Jovian radiation belt electron dynamics. While the sensitivity of chorus‐driven electron scattering to the ambient magnetospheric and wave parameters has been investigated, there is rather limited understanding regarding the extent to which the dynamic evolution of Jovian radiation belt electrons, under the impact of chorus wave scattering, depends on the electron distribution profiles. We adopt a group of reasonable initial conditions based upon the available observations and models for quantitative analyses. We find that inclusion of pitch angle variation in initial conditions can result in increased electron losses at lower pitch angles and substantially modify the pitch angle evolution profiles of > ~500 keV electrons, while variations of electron energy spectrum tend to modify the evolution primarily of 1 MeV and 5 MeV electrons. Our results explicitly demonstrate the importance to the radiation belt electron dynamics in the Jovian magnetosphere of the initial shape of the electron phase space density, and indicate the extent to which variations in electron energy spectrum and pitch angle distribution can contribute to the evolution of Jovian radiation belt electrons caused by chorus wave scattering.

Losses of Radiation Belt Energetic Particles by Encounters With Four of the Inner Moons of Jupiter

“…Furthermore, on basis of the distinct profiles of average particle lifetimes at different energies with different equatorial pitch angles corresponding to the moon absorption, it is inferred that the pitch angle distribution could likely follow the 90°-peaked type for energetic electrons but exhibit a V-type feature for energetic protons and that there may exist a peak of electron fluxes at ∼tens of MeV, a feature that currently cannot be resolved with the existing measurements that integrate over large energy ranges. As a consequence, the particle absorption by the Jovian moons needs to be incorporated with other important physical processes, including the wave-particle interactions (e.g.,Huang et al, 2018;Kollmann et al, 2018;Nénon et al, 2017Nénon et al, , 2018Shprits et al, 2012Shprits et al, , 2018Summers & Omura, 2007) and radial transport via interchange(Haggerty et al, 2019), diffusion(Lejosne & Kollmann, 2020), and convection(Hao et al, 2020), to pursue improved understanding of the complex variability of the Jupiter's radiation belt, which however is outside the scope of the present study and left for future work.…”