Directionality of solar flare hard X rays - Venera 13 observations

An analysis of 79 flares detected by the Venera 13 SIGNE 2 MS gamma-ray telescope is performed to indirectly search for directional effects in the hard (50-300 keV) X rays of solar flares. X-ray spectra were reconstructed assuming a power law fit. From the distribution of X-ray flares with respect to angle of observation and spectral index it is found that the primary-plus-albedo radiation is directive, and that the observed flare spectrum hardens toward the solar limb.