Comparison of Total Solar Irradiance with NASA/NSO Spectromagnetograph Data in Solar Cycles 22 and 23.

摘要

Accurate understanding of global solar variability is of clear astrophysical interest and is also vital to distinguish natural from anthropogenic causes of long-term changes in terrestrial climate. Daily averages of total solar irradiance (TSI) observations from several spacecraft radiometers over the past two decades show clear rotational and solar-cycle variations. The modeling of this variability through comparison of the spacecraft measurements with spatially resolved solar observations from both ground- and space-based instruments is highly refined. Two classes of solar features, dark sunspots and bright faculae, account for about 90% of the TSI variance. Although it is not yet clear whether the remaining discrepancies are observational or require additional sources of irradiance variability, the simple observation that TSI at the current solar maximum is very similar to the previous maximum while photospheric indicators of solar activity are lower in cycle 23 than in cycle 22 hints that more than solar activity is involved. This paper presents more detailed evidence to support this idea.