Structure of the magnetospheric magnetic field during magnetic storms

Abstract

We report the results of a study of the contributions of the largescale magnetospheric currents to the observed Dst variation. Ground‐based magnetometer data during four magnetic storms (January 27–30, 1985; November 23–27, 1986; January 14–16, 1988; and May 6–8, 1988) were used to calculate Dst , and the paraboloid model of the magnetospheric magnetic field [ Alexeev et al ., 1996] was used to determine the contribution of each magnetospheric current system. Input data for our model were the solar wind plasma parameters, the interplanetary magnetic field (IMF) B z , DMSP F6, F7, F8, and F9 satellite observations of precipitating auroral particles, and Active Magnetospheric Particle Tracer Explorers (AMPTE)/CCE satellite measurements of the total energy of the ring current ions with energy per charge between 1.5 and 300 keVq −1 . We found good agreement between observed and modeled magnetic fields during the main phase of the magnetic storms. Using the paraboloid model, we have determined the contributions to Dst of different magnetospheric current systems including the magnetopause current B CF , the symmetric ring current B R , and the geotail current B T ‐Such separation shows that values of B T and B CF are comparable with the value of B R during the main phase of the storms. During the recovery phase the effect of B R predominates.