Short duration solar microwave bursts and associated soft X-ray emission

During the time period of November 1968 to March 1970, 259 15.4 GHz impulsive microwave bursts have been identified of which 147 had associated 2–12 Å soft X-ray bursts. Average durations, rise times, and decay times for the microwave bursts are 2.9 ± 2.4 min, 0.9 ± 0.8 min, and 2.2 ± 2.1 min, respectively.Total durations and decay times for the X-ray events display a wide range of values from a few minutes to several hours. Rise times for 50 % of the events fell in the range of 2 to 7 min. A significant fraction (32 %) of the X-ray events may exhibit a flux enhancement prior to the main outburst.For 85 % of the flare cases, the X-ray event begins simultaneously with or before the microwave event. In 91 % of the cases the X-ray event peaks later than the microwave event. The average delay is 3.0 ± 1.9 min with 50 % of cases in the range of 0 to 4 min.The X-ray flux increases are significantly correlated with the microwave flux, increases, having a correlation coefficient of 0.43 (> 99.9 % confident).This work was supported in part by the Office of Naval Research under contract NOOO14-68-A-0196-0009 and the National Aeronautics and Space Administration through grant NGL-16-001-002.