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1991 June 06 (M1.2)

A GOES M1.2 solar flare occurred on 1991 June 06. 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 07:03 (25380 s), peaked at 07:09 (25740 s) and ended at 07:22 (26520 s) UT (GOES Geophysical Data Website). OSSE received a BATSE transient trigger at 25467 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 ~155 s time interval (25420-25595 s). The flare continued on at weak emmision for about 400 s after this time interval, but more significant data were obtained from integrating over only the bulk of the flare due to better results from the background subtraction. 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 -5.0 below a break energy of ~105 keV to about -3.7 above the break energy fit the data better than a single power law. The total fluence above 50 keV was 141.9 +/- 2.9 photons cm-2.

Figure 1

Figure 2

Last revised: 26 Jul 1999