New Method of Forecasting Geomagnetic Activity using Features of the Solar Corona

Abstract

EARLIER studies^1,2 have shown that a geomagnetic disturbance will occur when, and only when, a coronal formation is directed towards the Earth. An idea of the features and the temporal changes of the solar corona which are not currently observable can be acquired through the known relations between coronal formations and prominences. It is also necessary to realize that the coronal structure is formed by local magnetic fields, the extent and temporal stability of which are studied by means of prominences and the chromospheric structure in general. Coronal formations can be divided into four groups: helmets, streams, equatorial helmet of the minimum type and polar rays. Streams are characterized by a relative instability of the local magnetic fields at their base, which is displayed especially by the occurrence of unstable filaments, surges and a changing chromospheric structure. The remaining coronal formations are characterized by relatively stable conditions in the chromosphere and the photosphere.