Precipitation and energization of relativistic radiation belt electrons induced by ULF oscillations in the magnetosphere
There is a renewed interest in the study of the radiation belts with the recent launch of the Van Allen Probes satellites. The mechanisms that drive the global response of the radiation belts to geomagnetic storms are not yet well understood. Global simulations using magnetohydrodynamics (MHD) model fields as drivers provide a valuable tool for studying the dynamics of these MeV energetic particles. ACE satellite measurements of the MHD solar wind parameters are used as the upstream boundary condition for the Lyon-Fedder-Mobarry (LFM) 3D MHD code calculation of fields, used to drive electrons in 2D and 3D test particle simulations. In this study simulations were performed to investigate energization and loss of energetic radiation belt electrons. The response of the radiation belts to a CME-shock driven storm on January 21, 2005 during the MINIS balloon campaign was investigated, focusing on precipitation mechanisms by which Ultra Low Frequency (ULF) waves influence the radiation belt population. ULF wave modulation of MeV electron precipitation loss to the atmosphere has been reported in this and other balloon-borne measurements of X-ray bremsstrahlung and was observed in the simulations. Next, a pair of solar wind structures identified as Corotating Interaction Regions (CIR) in solar wind plasma measurements from the ACE satellite were studied during approach to the recent extended solar minimum. Such structures have previously been determined to be geoeffective in producing enhanced outer zone radiation belt electron fluxes, on average greater than at solar maximum. This study provides a comparison of 2D and 3D particle dynamics in MHD simulation fields, incorporating the additional diffusive feature of Shabansky orbit trapping of electrons in the magnetic minima on the dayside above and below the equatorial plane.
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