A stable cyclicity of correlation coefficients Kcorr for some solar activity
indices versus F10,7 was found after monthly averages values analysis. These
indices are: Wolf numbers, 10,7 cm radio flux F10,7, 0,1-0,8 nm background, the
total solar irradiance, Mg II UV-index (280 nm core to wing ratio) and counts
of flares. The correlation coefficients of the linear regression of these solar
activity indices versus F10,7 were analyzed for every year in solar cycles 21 -
23. We found out that the values of yearly determined correlation coefficients
Kcorr for solar activity indices versus F10,7 show the cyclic variations with
stable period closed to half length of 11-year cycle (5,5 years approximately)Comment: 113pages, 5 figures, 2 table