Coronal mass ejections and type II radio bursts

Abstract

Coronal mass ejections (CMEs) and shock wave induced radio bursts (type II) are reviewed. CMEs are — beneath flare blast waves — invoked to be the drivers of type II burst emitting super-Alfvénic disturbances. The paper focuses on the available experimental evidence for this assumption. For instance, the apparent contradiction is discussed between measured speeds of potential shock drivers and their observed type II burst association. Further, several examples are presented for recognizing CMEs by the appearance of other characteristic nonthermal radio signatures. Open problems are assembled which should be newly attact by high time and frequency resolution decimeter and meter wave radio spectral and imaging observations from ground combined with visible light and X-ray imaging data from YOHKOH and SOHO space experiments. The paper shows that radio observations in general, and especially the radiation of shock accelerated electrons, constitute a unique access to the structure and the dynamics of the coronal magnetoplasma. This is important for understanding the timing and the sites of energy release processes in the solar corona and for studying the physics of collisionless shock waves in space plasmas.