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1991 December 25 (M1.4)

A GOES M1.4 solar flare occurred on 1991 December 25 at an H-alpha location of S15E37 (heliographic coordinates). The soft X-ray flux began at 12:53 (46380 s), peaked at 13:06 (47160 s) and ended at 13:18 (47880 s) UT (GOES Geophysical Data Website). OSSE received a BATSE transient trigger at 46457 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 duration of the flare, and significant data were recorded by this detector.

Significant emmission of up to about 200 keV was observed during a ~135 s time interval (46445-46580 s). Count rate time profiles in various energy windows at a temporal resolution of ~8 s are shown in Figure 1. A representative count spectrum is shown in Figure 2. A single power law with an index of about -4.9 was used to fit the data. The total fluence above 50 keV was 258.6 +/- 5.8 photons cm-2.

Figure 1

Figure 2

Last revised: 16 Jul 1999