Energy Sources for Trapped Solar Energetic Ions

During magnetic storms, solar energetic particles (SEPs) can reach the inner magnetosphere and become trapped. We will evaluate the extent to which SEPs trapped in the magnetosphere gain energy after they enter the magnetosphere. We will examine the energy dependence of entry processes, acceleration as the particles move through the magnetosphere and processes affecting the SEPs after they are trapped. The particles might simply retain the energy they possessed before entering the magnetosphere, or they might gain most of their energy after entering the magnetosphere. The entry and trapping process may favor particles in certain energy ranges such that the energy spectrum of the trapped distribution is substantially different from the upstream particles. To examine these energization processes, we apply physics based models of SEPs entry into and motion through the magnetosphere during magnetic storms. We use MHD simulations driven by the solar wind and interplanetary magnetic field (IMF) upstream of the magnetosphere and particle tracing calculations in the time dependent electric and magnetic fields from the MHD simulations. Results suggest that different storms have contrasting energization processes. In particular, storms on November 24, 2001 and November 20, 2003 will be examined.