Flare fragmentation and type III productivity in the 1980 June 27 flare

We present observations of the solar flare on 1980 June 27, 16:14 16:33 UT, which was observed by a balloon-borne 300 cm² phoswich hard X-ray detector and by the IKARUS radio spectrometer. This flare shows intense hard X-ray (HXR) emission and an extreme productivity of (at least 754) type III bursts at 200 400 MHz. A linear correlation was found between the type III burst rate and the HXR fluence, with a coefficient of ≈ 7.6 × 10²⁷ photons keV^-1 per type III burst at 20 keV. The occurrence of ≈ 10 type III bursts per second, and also the even higher rate of millisecond spikes, suggests a high degree of fragmentation in the acceleration region. This high quantization of injected beams, assuming the thick-target model, shows up in a linear relationship between hard X-ray fluence and the type III rate, but not as fine structures in the HXR time profile. The generation of a superhot isothermal HXR component in the decay phase of the flare coincides with the fade-out of type III production.