Nightside Plasmasphere Variations Produced by the Stormtime Ring Current 

Liemohn, M.W., Gallagher, D.L., Ober, D.M., Ridley, A.J., Kozyra, J.U., 
C:son Brandt, P., Khazanov, G.V., Adrian, M.L. 


A potential well is created in the nightside subauroral ionosphere by the 
closure currents of the stormtime partial ring current. The force of this 
electric field is self-consistently included in a simulation of the inner 
magnetospheric plasma dynamics. The presentation will focus on the magnetic 
storm of May 24, 2000, which was the first magnetic storm seen by the IMAGE 
satellite, providing global snapshots of the ring current and plasmasphere. 
Asymmetric hot ion morphologies persist through the main phase and into the 
recovery, indicating that strong field-aligned closure currents must be present, 
creating the anomalous potential well. It is seen that the feedback of this 
electric field on the ring current ions limits the size of the potential drop, 
and also reconfigures the pattern (compared with the results without feedback). 
Intense electric fields still persist at midlatitudes throughout the main phase 
of the storms, rapidly eroding the nightside plasmasphere. EUV observations show 
that the nightside outer plasmasphere (the region connected to the plasmaspheric 
tail) was significantly depleted during the main phase of the storm. The 
influence of the enhanced drift on plasmaspheric densities is examined and 
quantified. 

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Presented at the 2002 Spring A.G.U. Meeting, 
Washington, D.C., U.S.A., 28-31 May 2002