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O. R. White, G. de Toma (NCAR/HAO), G. A. Chapman, S. R. Walton, D. G. Preminger, A. M. Cookson (CSUN/SFO), K. L. Harvey (SPRC), W. C. Livingston (NSO/NOAO)
We present a study of Total Solar Irradiance (TSI) variations during solar cycles 22 and 23 from 1986 to the present. We will review the recent measurements of solar magnetism, solar activity, and radiative variability from both ground-based and space observatories and compare TSI observations with empirical models of solar irradiance variability based on facular and sunspot observations.
To estimate facular/plage and sunspot contribution to TSI we use the photometric indices derived from the SFO full-disk solar images from 1988 to the present in the CaIIK line at 393.4nm and in the red continuum at 672.3 nm. In these indices, each solar structure is included with its measured contrast and area. We also use the MgII core-to-wing index from space observatories as an alternative index for plages and network.
Comparison of the rising and maximum phases of the two solar cycles, shows that cycle 23 is magnetically weaker with sunspot and facular area almost a factor of two lower than in solar cycle 22. However, analysis of multi-wavelength observations indicate that different wavelengths respond differently to the decreased magnetic activity during solar cycle 23.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.