EUV97: Improvements to EUV irradiance modeling in the soft X-rays and FUV

EUV97 is a salar EUV empirical model that incorporates revised soft X-ray fluxes from the SOLRAD-11 satellite (1976-1979) and uses L alpha recently recalibrated to the UARS satellite (1991-present) SOLSTICE L alpha. The soft X-ray data have been revised from the original flux values using Mewe's spectral fits to the data. The recalibrated AE-E and SME L alpha datasets use UARS L alpha for absolute flux values to provide two solar cycles of L alpha irradiance extending back to 1977. L alpha is used by EUV97 as a proxy for chromospheric EUV irradiances. The EUV97 empirical solar model takes its heritage from the EUV91 model based on a multiple linear regression technique that fits soft X-ray and EUV irradiances to 10.7 cm flux for transition region and coronal emissions or to L alpha and He I 10830 Angstrom EW for chromospheric emissions.