Nonthermal radio signatures of coronal disturbances with and without coronal mass ejections

This paper demonstrates that the radio signature of nonthermal electrons can be a sensitive indicator of small scale energy release related to topological changes in coronal structures. This study presents data on two events from the Extreme-UV Imaging Telescope (EIT) and the Large Angle and Spectroscopic Coronagraph (LASCO) instruments, GOES soft X-ray data, and 40-800 MHz radio spectra of the Astrophysical Institute Potsdam (AIP). At first glance, the two events do not appear very different. Both are long duration soft X-ray events (LDEs). However, one event decays after a flare-related ejection of cold and hot matter into the lower corona causing only brightness changes in EIT and LASCO-C1 while the other event marks the onset of a coronal mass ejection (CME) that propagates with a leading-edge speed of #approx# 530 kms "1 between 2-30 R_sun. One characteristic difference between the two events is a 1.5 hours duration plateau between two energy release phases detected by the GOES soft X-ray flux curves. The formation of the CME appears during this soft X-ray flux stagnation. It is first detected in EIT and C1 and is announced by an unspectacular faint group of metric drift bursts starting in the spectral range 170-200 MHz (corresponding to a height interval in 1.2-1.3 R_sun for different density models). The burst group lasts for #propor to#3 min. During the later CME lift-off, the start frequency drift of a simultaneously appearing type IV continuum translates to a speed in the range 80-130 km s"-"1. The same speed is obtained from the change in height of leading CME features in LASCO-C1. The non-CME event shows a brief (five minutes) break during the rise of the soft X-ray flux curve, only. It is accompanied by a type IV continuum without start frequency drift and lacks metric type III burst activity. In the non-CME case a bright blob remains stable on the top of a loop arcade for more than 2 hours. The brightness decline of this blob corresponds to the soft X-ray LDE decay. (orig.)SIGLEAvailable from TIB Hannover: RR 7310(98-24) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman