SIMULTANEOUS OBSERVATIONS OF SOLAR FLARES WITH CGRO/OSSE AND YOHKOH/WBS


R.J. Murphy, G.H. Share, and M. Yoshimori

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We have identified five strong flares over the period from Oct. 1991 to Jan. 1999 for which data are available from both the CGRO/OSSE and Yohkoh/WBS instruments. OSSE observed four of these flares over the same time intervals as Yohkoh, but at large offset angles. These were the flares on 1991 Oct. 24, Oct. 27, Nov. 15, and 1998 Nov. 22. Due to an SAA passage, OSSE began observing the fifth flare (1997 Nov. 6) about 900 seconds after the gamma-ray peak observed by Yohkoh and detected high-energy neutrons. The gamma-ray count spectra from the first four flares were fit with a model consisting of a power law, a 2.223 MeV neutron-capture line, a narrow-line spectrum and a broad-line spectrum. There is good agreement between the two instruments in the total fluences recorded for the steeper spectra; OSSE fluences are a factor of two smaller for the harder spectra. The 1997 Nov. 6 flare had one of the hardest particle spectra yet observed. The OSSE neutron observations support this conclusion.

Details of OSSE flare observations from 1991 to 1999 can be found at: http://heseweb.nrl.navy.mil/gamma/solarflare/flarelib.htm.