DP 1 and DP 2 current systems for the March 22, 1979 substorms

Abstract

The March 22, 1979 substorm interval selected for analysis by the CDAW 6 has been investigated using a ground magnetic data inversion scheme which computes equivalent current patterns as well as real ionospheric and field aligned current distributions. These have been computed at 5‐minute increments during the two substorm intervals on this day. The computed results have been analyzed using a differential technique which permits us to isolate the current development which occurs during selected time intervals. We find that both DP 1 and DP 2 currents develop during the course of the substorm activity. The first substorm is characterized by the gradual enhancement of a DP 2 equivalent current system following the southward turning of the interplanetary magnetic field. The major magnetic disturbance associated with the expansion phase of the substorm is dominated by the development of a DP 1 current system. During the second interval which consists of several hours of magnetic disturbance, the DP 2 system grows to be much stronger and is the dominant contribution to much of the auroral magnetic activity. The peak of the activity during the second substorm interval appears to be composed of both strong DP 2 and DP 1 currents coexisting. Following the decay of the DP 1 system a strong DP 2 system continues to exist during the enhanced convection phase of the substorm.