On the Variability of the Apparent Solar Radius

Full-disk photometric solar images at a wavelength of 672.3 nm have been obtained daily since 1986 using the CFDT1 (Cartesian Full Disk Telescope No. 1). An analysis of these images from 1986 through the end of 2004 December has shown a peak-to-peak variation in the geocentric north-south solar radius of [image], approximately in phase with the solar cycle. The multiple correlation coefficient squared is [image]. While this correlation coefficient is small, due to the large number of data points, the level of significance is less than 0.02. The radius had a maximum value near the times of maximum activity for solar cycles 22 and 23.