Simulating the Effect of Energy and Pitch angle Mixed diffusion on Ring Current Electron dynamics Based on the STRIM Model

Wave-particle interaction is one of the most crucial processes driving energy transport and conversion in the Earth's inner magnetosphere, leading to acceleration and diffusion of energetic electrons. Accurate characterization of these interaction mechanisms is essential for advancing our understanding of energetic electron dynamics within the ring current/radiation belts. In this study, we investigate the influence of wave-particle interactions on the phase space density and its variations in the ring current using a kinetic ring current model STRIM. The bounce-averaged Fokker-Planck equation in a dipole magnetic field is solved via a stochastic differential equation (SDE) equation, and diffusion coefficients are derived based on statistically analyzed wave properties from the Van Allen Probes (RBSP). By comparing diffusion coefficients, we find that energy diffusion and cross-diffusion terms play significant roles in the overall diffusion process. Comparative analysis on the effects of pitch angle diffusion and cross-diffusion on ring current electrons is also conducted to deepen our understanding of the diffusion process driven by wave-particle interaction.