Ion Transport and Acceleration at Dipolarization Fronts: Large-Scale MHD-Test-Particle Simulations

During geomagnetic storms plasma pressure in the inner magnetosphere is controlled by energetic ions of tens to hundreds keV. Plasma pressure is the source of global storm-time currents, which control the distribution of magnetic field and couple the inner magnetosphere-ionosphere system. The buildup of hot ion population largely occurs in the form of localized discrete injections associated with sharp dipolarizations of magnetic field. The goal of this study is to investigate the mechanisms of ion transport and acceleration at dipolarization fronts. For the analysis we use large-scale test-particle simulations in the electromagnetic fields computed with a global magnetospheric MHD model with resolution sufficiently high to reproduce spatial and temporal evolution of dipolarization fronts.