Energetic radiation belt electron precipitation showing ULF modulation
1] The energization and loss processes for energetic radiation belt electrons are not yet well understood. Ultra Low Frequency (ULF) waves have been correlated with both enhancement in outer zone radiation belt electron flux and modulation of precipitation loss to the atmosphere. This study considers the effects of ULF waves in the Pc-4 to Pc-5 period range (45 s\textendash600 s) on electron loss to the atmosphere on a time scale of several minutes. 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 a 3D test particle simulation that keeps track of attributes like energy, pitch-angle and L-shell. The simulation results are compared with balloon observations obtained during the January 21, 2005 CME-shock event. Rapid loss of 20 keV to 1.5 MeV electrons was detected by balloon-borne measurements ofbremsstrahlungX-rays during the MINIS campaign following the shock arrival at Earth. The global precipitation response of the radiation belts to this CME-shock driven storm was investigated focusing on their interaction with ULF waves. A primary cause for the precipitation modulation seen in both the simulation and the MINIS campaign is suggested based on the lowering of mirror points due to compressional magnetic field oscillations.
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Geophysical Research Letters
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