Extreme Ultraviolet Solar Spectral Irradiance Measurements and Model for GOES-R+

The highly variable extreme ultraviolet (EUV) solar spectral irradiance is a primary energy input to the upper atmosphere. Quantification of the solar EUV is critical for the specification of the state of the thermosphere and ionosphere. The EUV and X-ray Irradiance Sensors (EXIS) for the next generation of Geostationary Operation Environmental Satellites (GOES-R+) will monitor the solar irradiance in this wavelength range. In addition to continuing the historical record of the soft X-ray 0.05-0.4 nm and 0.1-0.8 nm bands, the EUV Sensor on EXIS will also measure specific solar emission features that will allow for the reconstruction of the full spectral irradiance from 5-127 nm. The specific measurements are the emission line irradiances from the solar corona at 28.4 nm (Fe XV); from the transition region at 25.6 nm (He II), 30.4 nm (He II), 121.6 nm (H I), and 140.5 nm (Si IV and O IV); and from the chromosphere at 117.5 nm (CIII) and 133.5 nm (CII), plus the chromospheric Mg II Core-to-Wing ratio in the 275-285 nm range. Encompassing emissions from the layers of the solar atmosphere that are the source of the EUV irradiance, these measurements will be used in an empirically derived proxy model to determine the EUV spectral irradiance. The primary EUV data product will be the the irradiance from 0-115 nm in 5-nm bins plus HI Ly-alpha at 121.6 nm at a time cadence of 30 seconds. I will describe the derivation of this model from the long term measurement record of the Solar EUV Experiment (SEE) on the NASA TIMED satellite, and from the EUV Variability Experiment on the NASA SDO satellite. The behavior and uses of the EXIS data product and proxy model will be explored.