ISTP Solar Maximum Extended Science Program

Abstract

We have studied the entry of solar energetic particles (SEPS) into the magnetosphere by following particles in the time dependent magnetic and electric field from global magnetohydrodynamic (MHD) simulations of the magnetosphere. The MHD simulations can either be for idealized interplanetary magnetic field (IMF) conditions, or for upstream conditions measured by spacecraft. An important part of the analysis is understanding the response of the magnetosphere to the IMF conditions. In the idealized case, the MHD simulation included a steady interplanetary magnetic field (IMF) B(sub x), velocity and density, while the B(sub y) and B(sub z) components were varied from southward IMF to dawnward and finally to northward IMF. We launched more than ten million protons, as well as about 1 million He-3 ions and a few thousand electrons upstream of the magnetosphere into the solar wind. They were initialized using a kappa distribution, which is a power law distribution with a power law coefficient of 1.5 at high energies. The particles had energies between 0. 1 and 50 MeV. The particles were run in time dependent MHD fields that were advanced in time as the particles moved through the system.