Spatial distribution of relativistic electron precipitation during a radiation belt depletion event

Abstract

We present observations from the NOAA-15 MEPED telescopes during a radiation belt depletion event on January 19-20, 2000 to investigate the spatial extent of electron precipitation during this interval. Precipitation mapped to the equatorial plane was confined to radial distances less than ∼6.5 Earth radii, indicating that precipitation was not the direct cause of the decrease in trapped flux observed by GOES. We found an enhanced day-night magnetic field asymmetry during the event, suggesting that magnetopause losses may have been responsible. Precipitation at lower L-values was observed by POES on the dusk passes (18:30-21:00 MLT), but not on the dawn passes, and was observed in conjugate hemispheres. These observations suggest that both precipitation and magnetopause losses were acting during this flux depletion event. © 2010 by the American Geophysical Union.