Spectral characteristics of high energy gamma ray solar flares

The gamma-ray telescope GAMMA-1 has registed gamma-emission in the range 30-2000 MeV from two solar flares. Spectral analysis with the use of maximum likelihood and maximum entropy methods has revealed differences in gamma-ray production mechanisms. In the impulsive March 26, 1991 event high energy gamma-rays originate exclusively as a bremsstrahlung of primary accelerated electrons. In contrast, the gamma ray emission of the extended phase of June 15, 1991 flare is mainly due to the decay of neutral pions. The average spectral index for primary nucleons was -3.6. Evolution of the spectra for both flares shows tendency to a decrease of the primary particles mean energies with time.