Comparative study of the flare-burst association for post-maximum periods of consecutive solar cycles

Occurrences of flare-associated microwave bursts as well as peak flux spectra were examined relation to the pre-a and post-maximum phases of the respective flares during the post-maximum period of two consecutive solar cycles, i.e., 1969-72 and 1980-82. Results obtained are: (i) About 76% of the flare-associated bursts occur in the pre-maximum phase and the remaining 24% occur in the post-maximum phase irrespective of the flare classification, intensity-wise or area-wise, for the 20th solar cycle, whereas these values are 65% and 35% for the 21st cycle. (ii) Impulsive and gradual-rise-and-fall bursts are relatively more abundant in the pre-maximum phase of flares for the 20th cycle, whereas impulsive, complex and simple bursts are more abundant in the 21st cycle. (iii) Peak flux spectra of impulsive bursts are mainly of the inverted-U type and gradual-rise-and-fall bursts are of the increasing-with-frequency type for the 20th cycle. For the 21st cycle the spectra of impulsive bursts are mainly of the increasing and inverted-U type, whereas those of the complex and simple types are mainly of the inverted-U type. (author). 1 fig., 4 tabs., 7 refs