The contribution of the albedo for photons to the intensity of hard X-ray emission of solar flares

Abstract

The albedo contribution to the total hard X-ray solar-flare emission has been considered. First, the distribution of primary hard X-ray photons localized along the flare loop was found, and finally, the Monte Carlo calculations of the Compton scattered hard X-ray photons were performed. The albedo for photons was shown to contribute to the total X-ray flux only in the energy range from 30 to 100 keV. The backscattered photon flux depends on the loop's position and on the localization of the source of primary radiation along the loop. For an isotropic distribution of primary photons, the backscattered photons’ contribution to the total flux is maximal for the loop in the center of the Sun and reduces when shifting to a limb. In the case of an anisotropic source the angle at which the contribution is maximal depends on the degree of anisotropy and on X-ray directivity in the source.