On the formation of the storm-time ring current belt

Abstract

It is shown that the formation of the ring current belt during geomagnetic storms is not a result of an enhanced convection which is directly driven by the solar wind and that substorm processes are crucial in populating the ring current belt by O+ ions. In order to demonstrate our result, it is shown that the development of the ring current belt is closely related to the upward field-aligned currents associated with magnetospheric substorms. Three periods were chosen for this particular study, based primarily on the availability of the needed data: March 17-19, 1978, March 20-21, 1990, and November 3-5, 1993. The correlation coefficients obtained were 0.33 between the corrected Dst and the directly driven component, indicating that the formation of the ring current belt is not a result of an enhanced convection. On the other hand, the correlation coefficient between the corrected Dst and the unloading component is 0.81. Therefore it may be concluded that the unloading component, or, more specifically, the magnetosphere-ionosphere coupling process associated with the unloading component of substorms, plays an important role in the development of the ring current belt. Our result is consistent with observations that O+ ions are often a dominant component in the storm-time ring current belt [Daglis, 1997]. Copyright 2000 by the American Geophysical Union.