Solar Flares and Associated 2800 Mc/sec (10.7 Cm) Radiation.

Study of 2800 Mc/sec solar radiation at the time of 213 flares and 173 subflares has shown distinctive radio events associated with 57 per cent of the flares and 19 per cent of the subflares. The flare-associated distinctive events at 2800 Mc/sec can be described by essentially the same types and categories already used to report outstanding disturbances at this radio frequency: single bursts; single-simple bursts with and without a postburst increase; single-complex bursts with and without a postburst increase; gradual rises and falls of flux. In addition, there is the designation "null," or no distinctive event. There is strong evidence that there is an outstanding event or disturbance in 2800 Mc/sec solar radiation only when a flare or subflare is in progress. Time relationships between Ha flares and 2800 Mc/sec events suggest that two quite different types of phenomena may be represented in the flare-associated 2800 Mc/sec radiation. One is a sudden burst- type feature which occurs during the rise to maximum of the Ha flare. The other is the more gradual rise and fall of ffux and "postburst increase," which lasts as long as, or longer than, the flare itself. Both types of phenomena appear to start with the Ha flare. Flares associated with large "postburst increases" or "gradual rises and falls" show a high concentration toward the central part of the solar disk. This is not the case for the strictly "burst-type" disturbances. The importance of the flare, the position of the flare on the solar disk, and accompanying ionospheric disturbances are considered with respect to the form and energy excess of the associated events at 2800 Mc/sec.