Solar extreme-ultraviolet irradiance for general circulation models

Recent measurements of the solar extreme-ultraviolet spectrum provide high-resolution spectral irradiance that can be used for calculating ionization and dissociation rates in the upper atmosphere and for providing improved proxy-based models of the solar spectrum. These are crucial inputs for global time-dependent general circulation models of the thermosphere and ionosphere, but computational economies require that a lower-resolution spectrum be used in the calculations without excessive loss of accuracy. The problem is compounded by the photoelectrons generated by ionization, which cause further ionization and dissociation of atmospheric gases. We describe a method for using solar spectral measurements or models to calculate ionization and dissociation rates throughout the upper atmosphere, including photoelectron effects, that is more accurate and more efficient than its predecessors. Examples of use with measurements from the Solar EUV Experiment on the TIMED satellite and with the EUVAC model are given, and an example calculation using the National Center for Atmospheric Research thermosphere-ionosphere-electrodynamics general circulation model is shown.