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1999 August 02 (C6.6)

A GOES C6.6 solar flare occurred on 1999 August 02 at an H-alpha location of S30W29 (heliographic coordinates). The soft X-ray flux began at 11:48 (42480 s), peaked at 11:52 (42720 s), and ended at 11:59 (43140 s) UT (GOES Geophysical Data Web Site). OSSE received a BATSE solar-flare trigger at 42563 s. All OSSE detectors were already aimed towards the sun. Two detectors remained aimed at the sun throughout the entire flare while the other two detectors initiated a standard on-source-off-source viewing strategy.

Significant gamma-ray emission to ~500 keV was observed lasting until about 42770 s UT with two peaks of emission at ~42700 s and 42720 s. Count rate time profiles in various energy windows at a temporal resolution of ~8 s are shown in Figure 1. Figure 2 shows a representative count spectrum obtained from one Sun-pointed detector integrated over the time period 42678-42776 s UT (98 seconds). The electron bremsstrahlung component was well-fit with a simple power law having a spectral index of ~4.22. The excess above the power law above 600 kev might be due to nuclear emission, but no evidence for narrow lines was observed.

Figure 1

Figure 2

Last revised: 11 Dec 1997