Decay of the magnetospheric ring current: A Monte Carlo simulation

Abstract

The decay of the magnetospheric ring current during the great geomagnetic storm of February 1986 has been modeled by using a Monte Carlo type calculation. The model is two-dimensional in nature and considers charge exchange, elastic and ionizing collisions, and Coulomb scattering as possible interaction processes between ring current ions and the upper atmosphere. For the main constituents of the ring current, H+ and O+ ions, the evolution of the distribution functions of relevant ion parameters and of the total energy stored in the ring current is determined as a function of time during the recovery phase. The results of the simulation prove that at least for the modeled geomagnetic storm, charge exchange is the dominant energy loss process of the ring current. Moreover, the general behavior of the Dst index during the February 1986 storm is reproduced. Copyright 1997 by the American Geophysical Union.