Plasmaspheric influence of radiation belts during major geomagnetic 
storms

Jerry Goldstein, Daniel Bake, Bill Sandel, James Burch, 
Joseph Fennell


We investigate a possible causal relationship between erosion of the
plasmasphere and enhancement of the radiation belts during major
geomagnetic storms. The Earth\'s plasmasphere was observed by the
IMAGE EUV imager to be drastically reduced in size by the 2003
Halloween geomagnetic storm event. Before the storm the plasmapause
was seen at roughly 4 Earth radii (RE) geocentric distance; after
the storm, the plasmapause had moved inside 2 RE. This dramatic
erosion of the plasmasphere apparently had a profound effect on the
global distribution of the Van Allen radiation belts. Wave-particle
interactions inside the plasmasphere normally act to remove the
radiation belt electrons inside the slot region; however, in the
days following the 2003 Halloween storm's drastic plasmasphere
erosion, SAMPEX witnessed the formation of an extremely intense new
radiation belt in what was formerly the slot region. This chain of
events suggests that the plasmasphere configuration can have a
primary influence on the global radiation belt distribution. We
present preliminary results of the investigation of this possible
relationship for three major geomagnetic storms, using global images
of the plasmasphere side-by-side with in situ energetic particle
data. We discuss likely mechanisms for quickly accelerating
electrons to the high levels observed in the slot that normally is
devoid of such relativistic electrons.

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Presented at the 28th URSI General Assembly, New Delhi, India, 
23 - 29 October, 2005