Solar Extreme and Far Ultraviolet Radiation Modeling for Aeronomic Calculations

Modeling the upper atmosphere and ionospheres on the basis of a mathematical description of physical processes requires knowledge of ultraviolet radiation fluxes from the Sun as an integral part of the model. Aeronomic models of variations in the radiation flux in the region of extreme (EUV) and far (FUV) radiation, based mainly on the data of the last TIMED mission measurements of the solar spectrum, are proposed. The EUVT model describes variations in the 5-105 nm spectral region, which are responsible for the ionization of the main components of the earth's atmosphere. The FUVT model describes the flux changes in the 115-242 nm region, which determines heating of the upper atmosphere and the dissociation of molecular oxygen. Both models use the intensity of the hydrogen Lyman-alpha line as an input parameter, which can currently be considered as one of the main indices of solar activity and can be measured with relatively simpler photometers. A comparison of the results of model calculations with observations shows that the model error does not exceed 1-2% for the FUVT model, and 5.5% for EUVT, which is sufficient for calculating the parameters of the ionosphere and thermosphere.

Automated summary

This paper discusses the importance of understanding and utilizing ultraviolet radiation fluxes from the Sun in modeling the upper atmosphere and ionospheres based on mathematical descriptions of physical processes. It presents aeronomic models of variations in extreme and far ultraviolet radiation, and compares the model calculations with observations to show the accuracy of the models in predicting parameters of the ionosphere and thermosphere.