SOLAR FLARES OF AUGUST 28 AND 30 1966

We describe observations of the class 3+ flare of August 28, 1966, made at the Mount Wilson Observatory. This great proton flare followed the sequence: (1) Precursor flare; (2) Filament eruption; (3) Beginning in penumbra of large spot; (4) Rapid elongation in two strands; (5) Great spray and surface wave; (6) Rapid separation of two strands to maximum brightness; and (7) Slow spread of brightness and decay. The soft X-ray burst coincides with stages 3-6, decaying through stage 7; the hard (> 80 keV) burst coincides, but decays more rapidly. Considering a demi-cylinder of emitting material, the soft X-rays are explained by a 4-million-degree plasma, or at least a large flux of electrons with that amount of energy. Given this flux, the microwave burst is explained by synchrotron emission with the low frequency cut-off due to coronal absorption. The class-2 flare of August 30, 1966, is also discussed. © 1969 D. Reidel Publishing Company.