ИСТИНА

The correlation coefficients of the linear regression of six solar indices versus 10.7 cm radio flux F10.7 were analyzed in solar cycles 21, 22 and 23. We also analyzed the interconnection between these indices and F10.7 with help of the approximation by the polynomials of second order. The indices we've studied in this paper are: relative sunspot numbers - SSN, 530.3 nm coronal line flux – F530 the total solar irradiance - TSI, Mg II 280 nm core-to-wing ratio UV-index, Flare Index - FI and Counts of flares. In the most cases the regressions of these solar indices versus F10.7 are close to the linear regression except the moments of time near to the minimums and maximums of 11-year activity. For the linear regressions we found that the minimum values of correlation coefficients Kcorr (t) for the solar indices versus F10.7 and SSN occurred twice during the 11-year cycle.