Solar irradiance reference spectra for two solar active levels

Abstract

Two new composite solar irradiance reference spectra extending from 0.1 to 2400 nm are constructed using recent space measurements for two distinct time periods during solar cycle 22. For wavelengths above Lyman α, data were gathered from the instruments placed aboard three space platforms, the ATmospheric Laboratory for Applications and Science (ATLAS), the Upper Atmosphere Research Satellite (UARS) and the EUropean Retrieval Carrier (EURECA). Below Lyman α, data from an instrument flown on rockets are used. The two spectra obtained at the time of ATLAS 1 and 3 missions cover about half of the total solar cycle amplitude as gauged by the Mg II and F10.7 solar indices. The accuracy of the spectra varies from 40% in the X-ray to about 3% in the UV–visible, and near IR ranges. A comparison between the total solar irradiance obtained through integration of the reference spectra and their observed values at the time of the ATLAS missions shows agreements of the order of 1%.