34th Solar Physics Division Meeting, June 2003
Session 7 Photosphere and Chromosphere I
Poster, Monday, June 16, 2003, 3:30-5:00pm, Mezzanine

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[7.05] Reconstruction of Facular Brightening from Sunspot Deficit

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

It is well established that variations in the total solar irradiance S can be accurately reproduced using a model based on the competing influences of the darkening due to sunspots and brightening due to faculae. In order to reconstruct S before observations of faculae, measurements of sunspots alone have been used as a proxy for inferring the facular brightening. In this work, we would like to improve the inferred facular brightening as well as gain insight into the time variation of various solar activity indicators. We make use of the deficit (darkening) due to sunspots D and the brightness variation attributed to faculae, as measured either by the excess emission in the CaIIK line EK or the MgII core-wing ratio. The cross correlation of D with either facular quantity shows well defined peaks at zero and negative lags (in the sense that facular excess lags D). We conclude that dark features decay into bright features, to some extent, but some bright features form coincident with the dark features. From the cross correlation we create a window function which is convolved with D to obtain a predicted E. Comparison of the prediction with the actual value of E shows that E starts rising at the beginning of cycle 23 before its reconstruction does. It appears that the onset of solar activity as measured by facular brightening precedes the rise in our sunspot deficit. Possible causes are under investigation.

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

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