Source Structures of A Microwave Burst with Slow Frequency Drifton November 28, 1998

Guangli Huang and Hiroshi Nakajima (Nobeyama Radio Observatory)

An X3.3 flare occurred in NOAA 8395 together with a partial halo CMEreported by SOHO/LASCO on Nov. 28, 1998, between 05:25 and 07:50 UT withpeak time at 05:40 UT. The associated radio burst was also recorded byNobeyama Radioheliograph at 17 and 34 GHz and the radiospetrometerof Beijing Observatory at 2.6-3.8 GHz.

The burst source was composed of three parts in the diagram of theheliograph. The main part (source A) was located at a bright regionin SXT images with strong magnetic field, closely to a footpoint ofone soft X-ray loop. The second part (source B) was associated withthe other bright soft X-ray loop with weaker magnetic field. The thirdpart (source C) coincided with another soft x-ray loop with weakermagnetic field. Moreover, each loop in sources B and C seems to betriggered by being prolonged from the loop in source A. It wasobserved by the radiospectrometer that in thedecay phase there was a hump at 05:41-05:43 UT accompnied by very slowdrift from high to low frequencies corresponding to a speed of severaltens km/s. The source C at 17 GHz seems to correspondto the slow frequency drift component as follows. (1) The source C wasa newborn source in both the heliograph and SXT/HXT images which startedaround 05:41 UT. (2) The source C moved towards the limb, and its speedwas comparable with the estimated velocity from the spectrometer.

We discuss the possible relationship between the slow drift componentand coronal shock (CME).