Temporal fine structure in hard γ radiation in solar flares
Gal'per A. M., Zemskov V. M., Luchkov B. I., Ozerov Yu. V., Tugaenko V. Yu., Khodarovich A. M.
The time evolution of the γ radiation with an energy above 30 MeV from two powerful solar flares (26 March and 15 June 1991) has been measured and analyzed. The radiation was detected by the GAMMA-1 orbiting telescope. The γ flare of 26 March consisted of a main burst lasting 11 s and several weaker bursts repeating at intervals from 10 s to several minutes. A fine structure is observed in the bursts. It consists of isolated radiation peaks with a time scale of 0.1-0.3 s. It is suggested that the temporal structure of a y-ray burst corresponds to discrete particle-acceleration events during the solar flare and, possibly, to a bunching of accelerated beams. The time evolution of the flare on 15 June, with a duration ~2 h, also shows evidence of discrete radiation bursts.