Appropriate models of solar flux in X rays and extreme ultraviolet (EUV) bands are presented in the light of the present status of ion chemistry in the region 90--130 km and of reliable measurements of reaction rates, electron density, and ion composition. It is found that the EUV flux of Schmidtke [1976> and the X ray flux of Manson [1976> give the best agreement between observed and theoretical electron density profiles for low solar activity. The observed increase of electron density with solar activity yields increases of EUV flux by factors of 3 and 6 and of X ray flux by factors of 2 and 4 for moderate and high solar activity conditions, respectively. However, the values of ion composition computed with these fluxes show marked differences from the value experimentally observed, the implications of which are discussed.