Cyclic Variations in the Solar Radiation Fluxes at the Beginning of the 21st Century

Abstract: The solar activity in the current, that is, the 24-th, sunspot cycle is analyzed. Cyclic variations in the sunspot number (SSN) and radiation fluxes in various spectral ranges have been estimated in comparison with the general level of the solar radiation, which is traditionally determined by the radio emission flux $F_ {10.7} $ at a wavelength of 10.7 cm (2.8 GHz). The comparative analysis of the variations in the solar constant and solar indices in the UV range, which are important for modeling the state of the Earth's atmosphere, in the weak 24th cycle and strong 22nd and 23rd cycles showed relative differences in the amplitudes of variations from the minimum to the maximum of the cycle. The influence of the hysteresis effect between the activity indices and $F_ {10.7} $ in the 24-th cycle, which is considered here, makes it possible to refine the forecast of the UV indices and solar constant depending on the quadratic regression coefficients that associate the solar indices with $F_ {10.7} $ depending on the phase of the cycle.