Solar Spectral Irradiance Variability Comparisons of the SORCE SIM Instrument with Monitors of Solar Activity and Spectral Synthesis

Jerald Harder [] and Juan Fontenla, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder.

The SIM irradiance data set provides the temporal evolution of solar irradiance throughout ultraviolet, visible and infrared spectral regions (250-1600 nm). At some wavelengths in the ultraviolet, the SIM measurements exhibit variations similar to the Mg II core-to-wing ratio, but at visible and IR wavelengths they show similarities to Total Solar Irradiance (TSI) record, but with differing amplitudes, phases, and shapes relative to these standard monitors. The TSI can be explained as a complex mix of the various wavelength components observed by SIM. Further insight into the solar variability observed by SIM can be gained from comparing an analysis of the distribution of solar features as measured by PSPT (Precision Solar Photometric Telescope) in conjunction with spectral decomposition. Most of the observed behavior appears to be qualitatively explained by the observed solar surface features that directly relate to the magnetic activity but the IR variations first noted by Fontenla et al. (Astrophys. Journal Lett., 605, L85-L88, 2004) are prominent in this time series.