The Severe Geomagnetic Storm Group Generated by the Solar Activities in March 1989

Characteristics of the series of severe geomagnetic storms generated by several extraordinarily large solar flares occured in a super active region in March 1989 are analyzed in this paper in association with the location and importance of parent flares. The storm series consisted of at least four independent storms. The most reasonable parent flares for these storms can be selected from the flares with optical improtance equal to or greater than 2B, X-ray classification being X, and duration longer than 1.5 hours. The morphology of geomagnetic storms changed systematically as the flare region rotated from the east to the west of the helio-graphic central meridian, showing obviously the central meridian effect and the east-west asymmetry in the dependence of storm morphology on the flare location.