Paper#: 71
Poster #:
Session Name: Workshop 5C: Tail Processes
Room: West Ballroom
Day: Thursday
Time: 4:55-5:15 p.m.
Abstract Title: On the Relationship between Geomagnetic Substorms and Storms
PresentSurname: Clauer, C.R.
All Authors: C. Robert Clauer, M. Liemohn, J. Kozyra, V. Petrov
Abstract : There are two contrasting views on the formation of the ring current during geomagnetic storms. The conventional idea is that the ring current results from the accumulation of many substorms. Each substorm produces an enhanced westward induction electric field near the outer ring current boundary which brings particles in from the plasma sheet -- a process called the substorm injection. The particles become trapped on closed azimuthal drift paths and a westward ring current is produced by the gradient and curvature drifts of the charged particles. A new view asserts that the ring current results from a sustained enhancement of the convection electric field. The enhanced electric field moves Alfven layers inward thus energizing the plasma and also moving the ring current closer to the Earth. The ring current is asymmetric and only after the enhanced electric field is reduced do particles find themselves on closed drift paths and the ring current becomes symmetric during the recovery phase. A synthesis of new and old ideas may provide the correct understanding for the storm time ring current. Using a combination of model simulations and global observations we investigate the processes responsible for the development and decay of the ring current. The primary factor contributing to the growth of the ring current is a sustained enhancement of the convection electric field. Substorm expansions contribute fluctuations in the partial ring current which have time scales comparable to the substorm time scale. Variations in the density of the source particle population in the plasma sheet modulates the effectiveness of the electric field to produce ring current growth.