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Session 122 - The Sun.
Oral session, Thursday, January 18
Salon del Rey South, Hilton

[122.01] Modelling Variations in Total Solar Irradiance during Cycle 22

G. A. Chapman, A. M. Cookson, J. J. Dobias (San Fernando Obs., Cal State Northridge)

We have compared total solar irradiance from Nimbus-7 and ACRIM1 with ground- based photometry from the San Fernando Observatory (SFO). The ground-based photometry consisted of photometric sunspot deficits and a photometric facular index. In some instances, we have included UV data from NOAA-9. For Nimbus-7 data, from 30 May 1988 to 13 December 1993, using all three sets of data, we find for 745 days of data a coefficient of multiple correlation, R\^2, of 0.89. The value of the quiet sun irradiance was 1371.67 +/- 0.21 W/m\^2. For a subset of these Nimbus-7 data, the rms noise was 0.19 W/m\^2. For ACRIM1 data, for the period from March 1985 to July 1989 the value of R\^2 was 0.81 for 685 days of data. For this interval, only the photometric sunspot deficit and NOAA9 UV data were used. The quiet sun irradiance was 1366.96 +/- 0.21 W/m\^2. The Nimbus-7 analysis, from 30 May 1988 to 13 December 1993, covers the rise, peak, and decline for solar cycle 22. The residuals show no evidence of the rise and decline in irradiance that can be seen in the Nimbus-7 data. We conclude that, to an uncertainty of about 200 parts per million of the mean irradiance, sunspots, faculae, and the network appear to explain all of the long term variation in the total solar irradiance. This research has been partially supported by grants from NSF (ATM-9115111) and NASA (NAGW-3017). Most of the SFO observations have been obtained by students to numerous to list.

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