ELECTRON ACCELERATION DURING SUBSTORMS

THEMIS spacecraft located within the near-Earth plasma sheet have observed a series of magnetic field dipolarizations coupled with electron acceleration and intense plasma wave activity. In this study we use a combination of data analysis and simulations to investigate the acceleration of electrons during dipolarizations. A global magnetohydrodynamic (MHD) simulation of the interaction of the solar wind with the magnetosphere is used to determine the overall magnetospheric structure and dynamics. In the electric and magnetic fields from the MHD simulations, distributions of electrons are launched to understand their transport and acceleration during the dipolarization event. The electron large scale kinetic calculations indicate that adiabatic motion may not be sufficient to account for the observed energies implying that waves play an important role in electron acceleration. To study the effect of wave-particle interactions, particle in cell simulations have been carried out. The results show that both adiabatic acceleration (Fermi and betatron) and wave particle interactions are necessary to account for electron heating during substorm dipolarizations.