OBSERVATIONS OF SOLAR-FLARE GAMMA-RAY SPECTRA WITH THE HINOTORI SATELLITE

The Hinotori satellite observed eight γ-ray flares with energy spectra extending to energies of 7 MeV. Some of these spectra consist of two components of a hard continuum due to electron bremsstrahlung and γ-ray lines due to nuclear interactions. Several γ-ray lines are superposed on the continuum spectrum. Prominent γ-ray lines are the prompt de-excitation lines of 12C at 4.44 MeV and of 16O at 6.13 MeV and the neutron capture line at 2.22 MeV. The γ-ray line feature due to a complex of prompt de-excitation lines of 56Fe, 24Mg, 20Ne, and 28Si appears in the 1-2 MeV range. The accelerated proton energy spectra are derived from the observed values of ratio of the 2.22 MeV line fluence to the 4-7 MeV γ-ray (12C and 16O lines are dominant) fluence. The derived proton energy spectra are in agreement with those directly observed in interplanetary space. The deduced numbers of protons producing γ-ray lines are compared with that escaping from the Sun. The energy depositions of protons accelerated to energies above 10 MeV are derived from the γ-ray fluences.