GEM: Dipolarization and Particle Acceleration at Substorm Onset

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This project will use a combination of 3-dimensional magnetohydrodynamic (MHD) and test particle (ions and electrons) simulations to investigate the energization of particles during the unset of a magnetic substorm. Substorm onset in the magnetotail is characterized by a sudden "dipolarization," that is, return from a stretched tail-like to a more dipolar magnetic field, also interpreted as "current disruption." This reconfiguration is associated with a strong induced electric field, which is strongly localized in space as well as in time. The project will examine the relationship between various onset signatures, such as magnetic reconnection, dipolarization, and particle acceleration, and the spatial and temporal properties of energetic particle fluxes. The MHD/test particle simulations will be supplemented by kinetic particle-in-cell (PIC) simulations as well as data analyses. The data that will be used for comparisons with the simulation results will come from the Los Alamos geosynchronous satellites and from the NASA THEMIS mission.Magnetic substorm activity is a special manifestation of a universal plasma and field process, which involves energy storage in magnetic fields and the sudden release of this energy and its conversion to particle energy via magnetic reconnection and its consequences. Understanding the mechanisms by which particles are accelerated to high energies is an essential element of understanding and predicting space weather, as well as for understanding solar and astrophysical eruptive plasma/magnetic field processes.