Low frequency radio observations of the solar corona prior to the onset of a mass ejection event

Abstract

It is well known that the halo CMEs originating on the visible hemisphere of the Sun could give rise to the severest terrestrial consequences. Recent studies carried out with the YOHKOH soft X-ray data by various authors have shown that the presence of a S-shaped or an inverse S-shaped pattern is a common characteristic of the regions that were the site of halo CMEs. At present we are carrying out a statistical study of the forerunners of the CME events observed during the recent solar minimum period using the data obtained with the Gauribidanur radioheliograph along with those obtained from YOHKOH and SOHO. It was found that apart from the S-shaped pattern, the metric noise storm sources also seem to a forerunner for majority of the events. The initial results seems to indicate that the emergence of new magnetic flux from the sub-photospheric levels and its orientation with respect to the pre-existing field is the key factor. An analysis of the forerunners of the CMEs and some case studies will be presented in this talk.