Abstract
Substorms can occur in series such as during a geomagnetic storm or as isolated events. We have chosen an isolated substorm from the Dynamics Explorer-2 (DE-2) database and use the Expanding/ Contracting Polar Cap Model to study the substorm-related ionospheric electric fields and polar cap dynamics. The isolated event of October 21, 1981 took place during several consecutive DE-2 passes which occur before the onset, just after the onset, during the substorm maximum, and during the recovery phase of the substorm. The polar cap expands during the growth and expansion phases and contracts little throughout the recovery phase. Tail reconnection, however, dominates the recovery phase. A total of 4 × 108 webers of open flux were reconnected during the recovery phase and removed from the polar cap.
