Downloadable ContentDownload PDF
Facular And Sunspot Areas During Solar Cycles 22 And 23
We present an analysis of facular/network and sunspot areas (and their ratio) covering most of cycle 22 and all of cycle 23. The data are corrected areas (in microhemispheres) from full-disk solar images using two photometric telescopes at the San Fernando Observatory, CFDT1 and CFDT2. Images from CFDT2 have approximately twice the spatial resolution of CFDT1. Sunspot areas are obtained from red images where spots are determined as those pixels darker than ?8.5%. Facular/network areas are from Ca ii K-line images where facular/network pixels are brighter than 4.8%. Regressions of facular area versus spot area for CFDT1 give a slope term of 25. For CFDT2, the slope term is 33. The average ratio of facular to spot area for cycle 22 is 45 and for cycle 23 the ratio is 42. These values are substantially higher than those from earlier studies. The increase is due to a combination of higher spatial resolution and the removal of a correction factor in ?. For the 0.3 nm K-line images, the spot to facular/network ratio is 138 for six years of cycle 23. A relation is given for the dependence of facular/network area on contrast. The relationship of facular/network area to sunspot area is linear for data from both telescopes.