The Role of Mesoscale Electrodynamics in Ring Current Evolution: Global MHD and Test Particle Simulations

During geomagnetic storms ions are transported from the magnetotail into the inner magnetosphere and accelerated to energies of tens to hundreds of keV. These energetic ions become the dominant source of plasma pressure in the inner magnetosphere and this ring current system couples the inner magnetosphere and the ionosphere. Ion transport and acceleration can occur at different spatial and temporal scales ranging from global quasi-steady convection to localized impulsive injection events.

The goal of this study is to investigate the mechanisms and characteristics of ion plasma pressure buildup in the inner magnetosphere driven by self-consistent MHD electromagnetic fields. To this end we will use our new MHD code Gamera, a reinvention of the high-heritage LFM (Lyon-Fedder-Mobarry) code, to calculate self-consistent mesoscale electromagnetic fields under typical driving conditions. Then, using our test particle code CHIMP we will initialize ion macroparticles in the magnetotail with the properties of the computed plasma flow and follow their evolution to calculate ion phase space density (PSD) throughout the inner magnetosphere. Our analysis will focus on addressing the following science questions: What, if any, is the role of non-adiabatic effects? How does ion anisotropy affect the plasma pressure in the inner magnetosphere? How is energy density in the inner magnetosphere distributed in phase space, i.e. the spatial (radial and longitudinal) and velocity (energy and pitch-angle) dependence of the ion PSD.