MODELING IONOSPHERIC CONVECTION DURING A MAJOR GEOMAGNETIC STORM ON OCTOBER 22-23, 1981

Following, the passage of an interplanetary shock at approximately 050 0 UT, a major geomagnetic storm developed on October 22-23, 1981. Nume rous auroral substorms occurred during this storm leading to an AE ind ex greater than 1000 nT. We have used the expanding/contracting polar cap (ECPC) model (Moses et al., 1989) and data from the Dynamics Explo rer 2 spacecraft to study the ionospheric electric fields for 12 conse cutive traversals of the polar regions. The ECPC model can determine t he voltage drops across the dayside merging and nightside reconnection gaps. We determined the relationship of the AL index (i.e., the inten sity of the westward electrojet) to the nightside reconnection potenti al drop. An excellent linear correlation was found between the nightsi de reconnection gap voltage drop and the AL index. These results show that the solar wind strongly drives the magnetosphere-ionosphere syste m throughout the geomagnetic storm. A substantial level of dayside mer ging seems to occur throughout the event. Nightside reconnection varie s from satellite pass to satellite pass and within the substorm recove ry phase. We find that tail reconnection is an important feature of th e recovery phase of substorms.