Solar microwave burst classification and correlation with soft X-rays

A large sample of microwave bursts observed at the Metsahovi Radio Research Station during 1989-1992 was analysed and the corresponding active regions were classified. The burst-producing active regions could be divided into three types according to their burst features. The bursts recorded at 37 GHz (8 mm wavelength) were also compared with the GOES soft X-ray data. The gradual rise and fall type burst fluxes showed almost linear correlation with soft X-ray fluxes, but no common denominator could be found for those radio bursts that lacked a counterpart at soft X-rays. Most of the impulsive microwave bursts were found to start and peak just before the soft X-ray maximum, while many of the gradual bursts started soon after the X-ray onset and peaked after the X-ray maximum. The X-ray flux rise before microwave onset was found to correlate with the maximum X-ray flux, in both impulsive and gradual burst events, the correlation coefficient depending on the soft X-ray flux.