Refilling of the Plasmasphere as Seen by IMAGE EUV

B.R. Sandel (University of Arizona, Tucson, AZ 85721) and W.T. Forrester

Global imaging of the plasmasphere by the IMAGE Extreme Ultraviolet Imager
offers the opportunity to study the processes that supply ionospheric plasma
to the plasmasphere. One explicit manifestation of these processes is the
refilling of the plasmasphere after it has been depleted by erosion events
often triggered by magnetic storms. Plasmaspheric erosion associated with
storms effectively removes the outer portions of the plasmasphere in a few
hours, so that the plasmapause moves closer to Earth. Then, in the simplest
picture, resupply from the ionosphere restores the plasmasphere to an
equilibrium distribution over the course of several days. In reality, other
processes operate simultaneously, and these sometimes tend to obscure the
effects of refilling. We have found a few time intervals in which relatively
long quiet periods follow discrete storms. These are particularly suitable
for studies of refilling. Using these study periods, we characterize the rate
of refilling as a function of L and compare with existing models of this
process. We investigate the possible link between refilling processes and the
azimuthal structure commonly observed in the quiet-time plasmasphere.

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Presentation at the Yosemite Conference of Inner Magnetospheric Interactions,
3 - 6 February 2004, Yosemite, California, USA