Identification of the Source Region of a ``Halo'' Coronal Mass Ejection Using Meter-Wavelength Radio Data

Abstract

We present meter-wavelength observations of the solar corona close to the onset of the ``halo'' coronal mass ejection (CME) of 1998 January 21 and estimate the change in electron density with time through a reproduction of the observed two-dimensional radio brightness distribution using a ray-tracing technique. Our calculations show that the average density above the background in the southeast quadrant of the corona overlying the visible solar disk had increased significantly (from 0 to 18), in the aftermath of the CME liftoff. This indicates that the source region of the event must have been located at a lower level of the solar atmosphere in that area. The rate of mass injection corresponding to the above change in density was found to be ~8.8×10¹⁵ g hr^-1.