On the solar origins of intense geomagnetic storms observed during 6-11 March 1993

Intense geomagnetic storms with DST index less than or equal to-100 nT were recorded on 9 March and II March 1993 associated with solar activity on 6 March and 9-10 March, respectively. In this paper, we discuss the character istic features of the solar origins of the two events that gave rise to cor onal and interplanetary disturbances and as a consequence produced strong g eomagnetic activity at the Earth. The source of the activity in one case is attributed to a major 3M7.0 flare that occurred on 6 March 1993 and in the other case, to two large filament disruptions on the disk during 9-10 Marc h, 1993. Both these sources were found to be located near changing or varyi ng low-latitude coronal holes. They were also located close to the heliosph eric currents sheets. Distinct X-ray activity was observed for both the eve nts as observed by the Yohkoh SXT telescope. The detailed evolution and a c omparison of these events on the basis of Yohkoh soft X-ray observations ar e presented here.