Some Studies on Solar X-ray Flare-associated Optical Flares, Microwave Bursts & Sudden Ionospheric Disturbances

Abstract

Different classes of solar optical flares, microwave bursts at 4995 MHz and sudden ionospheric disturbances have been examined in relation to 1575 solar X-ray flares (or bursts) recorded in the 0.5.-3 A band by SOLRAD-9 satellite during the period December 1968 to March 1970. X-ray flares have been found to be associated with all these events, the overall percentage association values being 46.5, 60.5 and 47.2 respectively. Bright Ha flares have been found to be more effective in producing X-ray flares. In relation to microwave bursts, X-ray flares show greater association with gradual rise and fall flares and also with impulsive type of bursts. Peak flux spectra of X-ray flare-associated bursts under both these types show three distinct types of distribution, viz. ‘inverted U ' type Showing one peak (I), 'complex' or 'zigzag' type having more than one peak (II) and peak flux increasing with frequency (III).