A hard X-ray observation of a solar flare with 100 ms time resolution

A solar flare which occurred on 4 July 1974 was observed in hard X-rays with a balloon-borne detector. When analyzed with a time resolution of 100 ms, four 2 s long spikes are observed, which are correlated with decimetric emission. Spectral analysis shows that the hardest X-rays were produced during the decay phase of the burst, when the microwave emission reached its peak. It is argued that the fine time structure could either be a bounce time effect, or that it could be due to the electron acceleration mechanism.