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1991 December 27 (M1.3)A GOES M1.3 solar flare occurred on 1991 December 27. The location of the flare on the Solar surface is not known due to lack of an accompanying H-alpha event. The soft X-ray flux began at 11:06 (39960 s), peaked at 11:13 (40380 s) and ended at 11:22 (40920 s) UT (GOES Geophysical Data Web Site). OSSE received a BATSE transient trigger at 40007 s but did not respond because the four OSSE detectors were involved in a complicated chopping procedure to observe the Galactic center. Fortunately, one of the detectors happened to be pointed at the scan-angle position of the Sun for the bulk of the flare, and significant data were recorded by this detector. Significant emission of up to about 200 keV was observed during a ~130 s time interval (40065-40195 s). Count rate time profiles in various energy windows at a temporal resolution of ~16 s are shown in Figure 1. A representative count spectrum is shown in Figure 2. A broken power law which hardened from an index of about -5.2 below a break energy of ~145 keV to about -2.7 above the break energy fit the data better than a single power law. The total fluence above 50 keV was 524.9 +/- 9.3 photons cm-2. |
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