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1999 August 02 (X1.4)

A GOES X1.4 solar flare occurred on 1999 August 02 at an H-alpha location of S18W45 (heliographic coordinates). The soft X-ray flux began at 21:18 (76680 s), peaked at 21:25 (77100 s) and ended at 21:38 (77880 s) UT (GOES Geophysical Data Web Site). The Sun was an OSSE target during this period. Detectors one and two remained at the scan angle of the Sun for the duration of the flare but were partially occulted, while detectors three and four performed +/- 4.5 degree on-source-off-source viewing strategies. Significant data was recorded by detector three.

Significant emission of up to several MeV was observed during a ~139 s time interval (76906-77045 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 -4.2 below a break energy of ~125 keV to about -3.2 above the break energy fit the data better than a single power law. It appears that a second break is required at about 1 MeV to fit the higher energies. The total fluence above 50 keV was 3230 +/- 65 photons cm-2.

Figure 1

Figure 2

Last revised: 04 Aug 1999