Image of IMAGE in space

IMAGE Discovers Cause of Unusual Van Allen Belt Distortions

Plasmasphere Changes

Using IMAGE-EUV and SAMPEX data, it has been confirmed that plasmasphere erosion is a necessary condition for Earthward distortion of the Van Allen radiation belts. The belts are separated by a so-called 'slot region' devoid of high-energy electrons. During geomagnetic storms, the outer radiation belts can move Earthward causing the size of the slot region to decrease. Two recent IMAGE papers have now shown that this slot region shrinkage is directly related to erosion of the plasmasphere. Low frequency plasma waves that inhabit the plasmasphere can interact with Van Allen belt electrons and remove them from the slot region through a resonant interaction. When the plasmasphere is eroded, however, the Van Allen belt electrons are free to move inwards into the slot region without getting scattered by the plasmaspheric waves.

(2005: Goldstein et al.,; 2005: Baker et al.)

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Additional Information

Plasmasphere -The extension of Earth's ionosphere into space to altitudes of 10,000 kilometers or more, forming a tenuous region of charged particles that rotate with earth with a 24-hour period.

Plasmasheet - A region of the magnetotail in the equatorial plane where currents of particles are generated.

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Dr. S. Odenwald,, +1-301-286-6953
NSSDC, Mail Code 630, NASA Goddard Space Flight Center, Greenbelt, MD 20771
NASA Approval: J. L. Green,
Rev. 1.0.0, 24 July 2004, EVB II