Fine structural features of radio-frequency radiation of the solar flare of February 12, 2010

Solar radio emission records received at the IZMIRAN spectrograph (25–270 MHz) during the solar flare event of February 12, 2010 are analyzed. Different fine structures were observed in three large groups of type III bursts against a low continuum. According to data from the Nancay radioheliograph, sources of all three groups of bursts were located in one active region, 11046, and their emissions were accompanied by soft X-ray bursts (GOES satellite): C7.9 at 0721 UT, B9.6 at 0940 UT, and M8.3 at 1125 UT. After the first group of bursts, classical fiber bursts were observed in combination with reverse-drift fiber bursts with unusual arc drift. After the third (the most powerful) group, stable second-length pulsations and slow-drift fiber bursts were observed, the instantaneous frequency bands of which were an order of magnitude larger than the frequency band of classical fiber bursts, and the frequency drift was several times lower. More complex fiber bursts were observed in the weakest group in the time range 0940:39–0942:00 UT. They were narrow-band (～0.5 MHz) fiber bursts, periodically recurring in a narrow frequency band (5–6 MHz) during several seconds. The presence of many chaotically drifting ensembles of fibers, crossing and superimposing on one another, is a feature of this event. It is assumed that occurrence of these structures can be connected with the existence of many small shock fronts behind the leading edge of a coronal mass ejection.