Studies of energization of magnetospheric particles by substorm dipolarizations

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The goal of the proposed research is to model the fluxes of energetic particles (mostly electrons and protons) generated during substorm events. Enhanced fluxes of these particles are often observed by satellites at geostationary orbit in association with substorm dipolarizations. These particles often possess energies of hundreds of keVs and are capable of damaging satellite electronics resulting in significant economic losses for the industry. Despite many years of active research many questions regarding the energization process remain unanswered. We consider two scenarios of substrom dipolarizations: the tailward propagating edge of the transition from dipole to stretched magnetic field lines and earthward propagating electromagnetic pulse. Both scenarios lead to significant energization of the tail populations of electrons and protons and both have observational support. The first scenario is well supported by the ground-based observations, such as photometer observations of auroras and riometer observations of the ionospheric transmissivity, the second by in-situ satellite observations. Our modeling efforts will help to improve our understanding of the energization process of the charged particles and quantify their effects in the magnetosphere and ionosphere. Ultimately, we hope to be able to quantify the manifestations of the two energization scenarios both in space and in the ionosphere. This will allow us to distinguish the two and to reconcile the apparent disagreement between the ground-based and satellite observations.