The Shrinkage of Flare Radio Loops

Abstract

This Letter presents a direct example of the shrinkage of flare loops from the radio observation of a limb X3.1 flare occurring at 00:49 UT on 2002 August 24. The relation between the positions of X-ray and radio images reveals that this flare is a typical Masuda flare. The GOES X-ray flux shows a flat time variation, and the time variation of the radio flux at 17 and 35 GHz shows that the flare had only one intense energy injection at about 01:00 UT. In the rising phase of 9 minutes, the loop in the radio image at 34 GHz shrank by about 30%, suggesting a downward speed of approximately 13 km s-1. About 2 minutes after the peak of the intense energy injection, the shrinkage of the radio loop evolved into an expansion.