Some studies on solar microwave bursts in relation to the phases of the associated Hα-flares and their spectral nature

Abstract

Occurrences of the flare-associated microwave bursts as well as their peak flux and energy excess spectra have been examined in relation to the pre- and post-maximum phases of the respective flares during the period 1969-72. Results obtained are: (i) about 76% of the flare-associated bursts occur in the pre-maximum phase and the remaining 24% occurs in the post-maximum phase irrespective of the flare classification, intensity-wise or area-wise; (ii) impulsive and gradual rise and fall bursts are relatively more important in the pre-maximum phase while post burst increase bursts show comparatively higher occurrences in the post-maximum phase; (iii) peak flux and energy excess spectra of the concurrent microwave bursts in the pre-maximum phase of the flare are mostly of inverted U and increasing with frequency spectral types. Of these, impulsive bursts are predominantly of the inverted U and the grf bursts are of the increasing with frequency spectral type.