THE SOLAR CAUSES OF MAJOR GEOMAGNETIC STORMS

In this paper we reanalyse the set of ten major geomagnetic storms whi ch occurred between August 1978 and December 1979. We relate them to t he characteristics of the solar wind disturbances which caused them an d the solar sources of such disturbances as tracked by means of interp lanetary scintillation. It seems to us that the shock causing the sudd en commencement and the plasma behind it with an important long-lastin g B(z) south component (B(z)) are not necessarily parts of the same s tructure. We also found that the solar sources of all these disturbanc es were regions near central meridian containing both a coronal hole a nd a flare or, most frequently, an erupting prominence. A possible sce nario for the occurrence of these processes at the Sun is outlined, an d theoretical and observational support for it is provided.