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2000 April 04 (C9.7)

A GOES C9.7 solar flare occurred on 2000 April 04 at an H-alpha location of N16W66 (heliographic coordinates). The soft X-ray flux began at 15:12 (54720 s), peaked at 15:41 (56460 s), and ended at 16:05 (57900 s) UT (GOES Geophysical Data Web Site). OSSE received a BATSE solar-flare trigger at 55156 s and the four OSSE detectors slewed to the scan-angle position of the Sun and initiated +/- 4.5 degree on-source-off-source viewing strategies. Solar observations began at 55197 s UT.

Significant gamma-ray emission to >500 keV was observed lasting until about 56150 s UT with two peaks of emission at ~55210 s and 55400 s and a weaker inner peak. 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 55197-55574 s UT (377 seconds). The electron bremsstrahlung component was well-fit with a broken power having a break energy of ~90 keV. The power-law index was ~3.4 below the break energy and hardened to ~2.8 above. There was no evidence for nuclear lines. The electron bremsstrahlung power law was found to soften essentially continuously with time throughout the flare, from a power law index of ~3.0 before the peaks to ~3.5 at the end of the observation. There was a weak indication that the index may have hardened slightly across the second peak. There was an interplanetary particle event associated with this flare, with significant enhancements in both electrons and protons up to at least 30 MeV.

Figure 1

Figure 2

Last revised: 11 Dec 1997