AAS 200th meeting, Albuquerque, NM, June 2002
Session 57. Living with a Star
Display, Wednesday, June 5, 2002, 10:00am-7:00pm, SW Exhibit Hall

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[57.06] Predicting Total Solar Irradiance Using Sunspot Deficit Only

D.G. Preminger, S.R. Walton (San Fernando Observatory, Cal State Northridge)

It has been well established that variations in the total solar irradiance S can be accurately reproduced using a model based on the competing influences of sunspots and faculae. These models can, in principle, be used to reconstruct the value of S before accurate spacecraft measurements began in 1979. However, while sunspots have been well observed since the early seventeenth century, information about the faculae is not available for much of the period of interest. We are experimenting with a new technique to reconstruct the facular contribution to the total solar irradiance S from the sunspot signal.

The sunspot deficit Dr is well correlated with short-term variations in the total solar irradiance S. The total variation in the Ca~II~K line signal, \SigmaK, is correlated with long-term variations in S. Using the cross correlation of Dr and \SigmaK, we can obtain a window function that can be used to model \SigmaK from Dr. The cross correlation has five significant peaks at lags of zero to -4 solar rotations. The main peak is at a negative lag, in the sense that \SigmaK lags Dr. The fit to S using Dr and \SigmaK reconstructed in this way during cycle 22 yields a multiple regression coefficient R2 = 0.70.

This work was supported by NSF grant ATM-9912132 and NASA grants NAG5-7191 and NAG5-7778.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.