Energy sources for the ionosphere - A survey

The presented survey is mainly concerned with aspects of historical development, taking into account solar short wave radiation as the principal source of diurnal ionization. Attention is given to the integrated quantum flux in the solar XUV spectrum, the integrated energy flux spectrum of the sun after theoretical estimates prior to 1960, the integrated energy flux spectrum of the sun after recent space measurements, and the energy flux due to strong coronal emission lines. Solar radiation and the formation of ionospheric layers are considered, and a detailed discussion of the main ionospheric layers is given, taking into account the D-region, the E-region, and the F-region