Studies of solar flares using optical, X-ray and radio data

X-ray, radio, H-alpha, and 3835-A data for a number of solar flares identified as sources of X-ray bursts are compared and analyzed. Eight of the more distinctive flares are described in detail, the exact value of H-alpha intensity is determined, and the production of the H-alpha emission is considered. It is shown that: (1) there is a good correspondence between the rise and peak of H-alpha emission and hard X-ray flux; (2) the H-alpha surface brightness of hard and soft X-ray bursts is the same for flares of the same soft X-ray flux; (3) all multiple spikes correspond to different steps in optical flares development; (4) smaller flares produce no observed brightening; (5) there is evidence that the low chromospheric network is not heated by conduction from above; and (6) the flare H-alpha emission can be explained by direct excitation of a preflare cloud or prominence by the flare electrons and their secondaries.