On the Radio Signatures Associated with the Development of Coronal Mass Ejections

Abstract

The methods of radioastronomy are in important observational tool to explore magnetic energy releases in the solar corona. When combined with the useful diagnostics provided by observations in other wavelengths, namely with data from space missions such as Yohkoh, SOHO, and more recently RHESSI, these datasets allow us to track the progression of solar eruptive events from the low corona into the interplanetary medium. One of the most dramatic forms of solar activity, coronal mass ejections (CMEs) encompass a large range of spatial scales in a question of a few minutes. These go from the very small like current sheets, to small like active regions, to the very big like trans-equatorial loops and the transient seen in white light images (with angular extents in excess of 100 degrees for some events). Hence, in order to understand the CME phenomenon, its origin, and early development, we need a set of observations able to image the whole Sun with time cadences of the order of the second. Radio observations can do that presently. Multifrequency radio observations of the solar corona in the metric domain provide diagnostics of a wide variety of phenomena that occur in association CMEs. Radio imaging instruments can follow the processes leading to CME initiation, follow the expansion of the CME in the low corona, both on disk, and above the solar limb, and as such make the link with coronagraphic data. The characteristic signatures of the many CME related phenomena go from thermal emission of the eruptive cavity in the low corona, to direct imaging of the CME loops from synchrotron emission, to radio continua and shock associated emissions, recent progress on the understanding of the early development of CMEs, and on the coronal restructuring in the aftermath of the mass ejection, based on solar radio imaging from the Nancay Radioheliograph, is reviewed here.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html