Acceleration and extreme distortion within the Van Allen radiation belts during
the "Halloween" solar storms of 2003

S. Monk, D.N. Baker, S.G. Kanekal, X. Li, J. Goldstein, and J.L. Burch


The center of the outer Van Allen radiation belt is usually about 20000 to 25000
km away from Earth. This belt of high-energy electrons that are trapped on
magnetic field lines in near-Earth space was enhanced and driven into a highly
unusual configuration during the recent solar activity in late October and
November - known by scientists as the "Halloween Storm" of 2003. During and
following the Halloween Storm, the Van Allen belt electron population was
powerfully accelerated and redistributed inward. From November 1 to November 10,
the outer belt had its center only about 10000 km from Earth's equatorial
surface. As shown here using IMAGE spacecraft data, the Earth's ionized outer
atmosphere (plasmasphere) was displaced inward (to an unprecedented degree) in
October-November 2003, and concurrently the whole radiation belt structure was
transformed. The region between the Van Allen belts, normally devoid of
particles, became the location of highest radiation belt particle intensities.
Such a remarkable deformation of the entire magnetosphere has not previously
been witnessed and implies surprisingly powerful acceleration and loss processes
deep within Earth's magnetosphere.

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Presentation, Fall A.G.U. Meeting, San Francisco, CA, 13-17 December 2004