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1991 June 10 (C8.7)

A GOES C8.7 solar flare occurred on 1991 June 10. 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 21:23 (76980 s), peaked at 21:28 (77280 s) and ended at 21:39 (77940 s) UT (GOES Geophysical Data Website). OSSE received a BATSE transient trigger at 77219 s but the four OSSE detectors were already pointed at the scan-angle position of the Sun. Two of the four detectors then initiated +/- 4.5 degree on-source-off-source viewing strategies while the other two detectors remained pointed at the Sun. Because of the extreme DSA-angle of the Sun, however, the views of the top two detectors were obstructed and significant data were recorded by only the bottom two detectors.

Significant emission of up to about 300 keV was observed during a ~65 s time interval (77215-77280 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 steepened from an index of about -4.0 below a break energy of ~90 keV to about -5.1 above the break energy fit the data better than a single power law. The total fluence above 50 keV was 206.6 +/- 5.0 photons cm-2.

Figure 1

Figure 2

Last revised: 13 Jun 1999