Relation between X-ray and ultraviolet radiations of solar flares in ionization of the E-region

Data supplied by ionosphere stations on 20 solar flares was used to calculate the relative change in the velocity of ionization, and the latter was compared with the relative variation of the X-ray radiation of 8-20 A. The intensity of the X-ray radiation from the spectrum range of 8-165 A (responsible for the ionization) increases during the flare proportionally to the square root of the radiation of 8-20 A. During the intense flares, the contribution of the X-ray radiation to the ionization in the E range exceeds that of the ultraviolet radiation, amounting to 10-20% under calm conditions