TITLE:  Test-Particle Simulations with a Global Magnetospheric Model: Understanding Energetic Particle Loss through the Magnetopause

ABSTRACT:  In this presentation, I will describe the methodology we have developed to evolve large numbers of test-particles in electromagnetic fields generated via high-resolution global MHD simulations of the magnetosphere. The new tools have been recently applied to a number of outstanding problems in magnetospheric physics. In particular, motivated by recent observations by the NASA MMS and Van Allen Probes missions, we revisited the long-standing problem of energetic particle loss from the magnetosphere. Using our newly developed numerical tools, we explore the spatiotemporal characteristics of these losses and the role played by the dynamics of the magnetopause – including the Kelvin-Helmholtz instability -- in creating their magnetic local time and latitudinal dependence. I will conclude by briefly describing the work in progress that uses the test-particle approach to study the evolution of phase space density in the magnetosphere during geomagnetic storms and energetic particle injection events.