Solar Physics Division Meeting 2000, June 19-22
Session 1. Helioseismology, Magnetic Fields, Chromosphere and Transition Region
Display, Chair: C. U. Keller, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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[1.26] New Measurements of the Ratio of Facular to Sunspot Area

G. A. Chapman, A.M. Cookson, J.J. Dobias (SFO/CSUN)

We report new results on the ratio of facular area to sunspot area from a program of continuing photometric observations using the Cartesian Full Disk Telescopes at the San Fernando Observatory (SFO). The facular areas are determined from images obtained with a 1 nm bandpass K-line filter and the sunspot areas are determined from red images at 672 nm. On the K-line images faculae were identified by pixels that had a contrast equal to or greater than 4.8% divided by \mu. Previously, we found the average facular to spot area ratio was 16.7 ±0.5 during the latter part of solar cycle 22 (Chapman, Cookson & Dobias, 1997) and that there was a small but statistically significant rise in the ratio with time. If we take an average from the beginning of the K-line data (mid-1988) until the middle of 1996, \emph{excluding} days of zero sunspot area, the average ratio is 17.5 ±5.1. The average ratio from mid-1996 to the end of November 1999 is 12.6 ±4.8. \emph{Including} days of zero sunspot area for these same intervals we find an average ratio of 21.5 ±9.2 and 19.9 ±15.3, respectively. We have recently reprocessed our K-line images which have been photometrically cleaned (Walton et al. 1998). We can now reliably identify facular pixels with a contrast criterion of 2.4% resulting in an increase in the average facular to spot ratio of approximately three. This research has been partially supported by NSF Grant ATM-9504374 and NASA Grants NAGW-3017 and NAG5-4973.

\begin{center} References \end{center}

\noindent Chapman, G.A., Cookson, A.M. & Dobias, J.J. 1997, Ap.J. 482, 541.\smallskip

\noindent Walton, S.R., Chapman, G.A., Cookson, A.M., Dobias, J.J. and Preminger, D.G. 1998 Solar Phys. 179, 31.

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