Detailed spectra of the extreme ultraviolet solar flux at the earth were provided by instruments on the Atmosphere Explorer satellites. These data have been used for aeronomical purposes in a large number of studies. An important parameter for such studies is the rate of production of various ions through the photoionization process. This parameter, known as an ionization frequency, is the integral over wave-length of the product of the solar flux and the cross section for the ionization of the particular constituent. Thus the determination of the ionization rate is dependent on a good knowledge of the solar EUV intensities for the solar period in question. Over the past few years the EUV solar spectra that have been developed for use by aeronomers as reference spectra for such photochemical and ionospheric studies have been improved. In this paper we report the results of a redetermination of the most important ionization frequencies using the revised solar fluxes. The impact is found to be more significant at solar maximum, amounting to a reduction of 12--21% in the ionization frequencies of the major terrestrial thermospheric constituents for solar minimum conditions and 21--33% for solar maximum conditions. The corrections are apart from the ongoing debate concerning the absolute intensity of EUV solar flux measurements for the solar cycle 21 maximum period.