Simulation of dynamics of radiation belt electrons during geomagnetic storms driven by high speed solar wind streams

Satellite observations have shown that fluxes of relativistic electrons in the earth's radiation belts can vary by orders of magnitude during periods of high solar activity. Understanding the dynamic behavior of these particles is very important because they can disrupt wireless communication, impair space exploration and affect GPS navigation. We use two numerical methods to simulate the variations of energetic particles in the radiation belts. First, we develop a radial diffusion model with time-dependent boundary conditions and a Kp-dependent electron lifetime model. Using this model, we simulate a series of high-speed-stream declining-phase magnetic storm events. The results are consistent with spacecraft observations and show that radial diffusion can propagate the enhancement of phase space density from the outer boundary into the center of the outer radiation belt. The second part of the work adapts Nunn's Vlasov Hybrid Simulation method to an existing MHD-Particle simulation code, resulting in an efficient new method to calculate phase space density of energetic particles. We use the 1995 January storm event as a test case. Good agreement is obtained between the simulation results and measured phase space densities for this event. Simulating the dynamics of the radiation belts is one important part of global space weather modeling. The advance in radiation belt modeling can help us to better understand the physics behind these interesting and important phenomena