Importance of plasma injection events for energization of relativistic electrons in the Jovian magnetosphere

摘要

Effects of density decrease in plasma injection regions and a latitude-dependent wave normal angle distribution on the energization of electrons by whistler mode waves at Jupiter are investigated. Previous work showed that whistler mode waves could enhance the fluxes of a few MeV electrons by an order of magnitude on a time scale of 30 days. However, density decrease in plasma injection regions and latitude dependence of the wave normal angle distribution of waves were not considered. Because this information is difficult to obtain from available observations, we perform a sensitivity study to demonstrate that the effect of density decrease on energization of electrons becomes important when the density inside injection regions is reduced to 25% of that outside. We also investigate the effect of a latitude-dependent wave normal angle distribution on energization of electrons using a ray tracing program and demonstrate that a realistic latitude-dependent wave normal angle distribution increases the rate of pitch angle diffusion near the loss cone, and thus enhances the loss rate, of 1-3 MeV electrons. However, the flux of 10 MeV electrons is not significantly affected. Results of the work are useful for understanding energization of MeV electrons at Jupiter, especially when combined with observations from future missions.