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1991 December 14 (M1.6)

A GOES M1.6 solar flare occurred on 1991 December 14. 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 14:47 (53220 s), peaked at 14:51 (53460 s) and ended at 14:55 (53700 s) UT (GOES Geophysical Data Website). OSSE received a BATSE transient trigger at 53234 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 1.0 MeV was observed during a ~175 s time interval (53235-53410 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 broken power law which hardened from an index of about -3.7 below a break energy of ~195 keV to about -2.5 above the break energy fit the data better than a single power law. The total fluence above 50 keV was 303.9 +/- 5.2 photons cm-2.

Figure 1

Figure 2

Last revised: 16 Jul 1999