A Solar EUV Flux Model

Abstract

A model of the solar extreme ultraviolet (EUV) irradiance variability has been developed for aeronomical use and has been named SERF2 by the Solar Electromagnetic Radiation Flux Study. The model is valid between 1981 and 1989 and is based on the Atmosphere Explorer E (AE‐E) satellite EUV data set which is correlated with independent solar emissions measured during and after the AE‐E mission. Additionally, spectral modifications are made to the model based on 18 separate rocket flights for all levels of solar activity. Two daily measured solar emissions, the H Lyman α line at 121.6 nm observed by the Solar Mesosphere Explorer satellite and the Ottawa 10.7‐cm radio flux observed at the ground, are used in the model as indices for full‐disk solar EUV chromospheric irradiance variations and transition region‐coronal irradiance variations, respectively. The model wavelength equation coefficients are presented in tabular form for 39 wavelength groups or discrete lines from 1.9 to 105.0 nm along with spectral weighting function coefficients which modify the irradiance magnitudes based upon model wavelength fits to rocket‐observed spectra. The model satisfies the general constraint of duplicating rocket‐observed EUV irradiance for a wide variety of solar activity conditions. The model development is discussed, an example calculation is given, and the comparisons with constraining rocket data sets are shown.