ИСТИНА

An important aspect of solar-terrestrial relations is the complex of phenomena associated with the effects of ultraviolet, X-ray and gamma radiation from solar flares (SF) on the Earth's ionosphere. This radiation captures all layers of the ionosphere, and even the stratosphere. The present work is aimed at analyzing the effects of SF on the parameters of the lower and upper ionosphere, which affect the properties of radio waves in the Earth-ionosphere waveguide. Bursts of X-ray fluxes affect the spectral structure of global low-frequency electromagnetic resonances in the Earth-ionosphere cavity (7.8-35 Hz), known as Schumann resonances (SR). Changes in the amplitude-phase characteristics of signals on ultra-long-wave radio paths and SR frequencies are a sensitive indicator of changes in the state of the ionosphere. To carry out an analysis of the SF effect on the ionosphere, an idealized model was constructed, with the help of which analytical expressions as the functions of altitude and time were obtained for the rate of formation of ion-electron pairs and for changes in the concentrations of electrons and ions. The increase in the conductivity of the D-layer of the ionosphere obtained according to the model, followed by a decrease in the depth of penetration of electromagnetic ULF waves into the upper wall of the Earth-ionosphere waveguide, predicts that the weighted average frequency of the SR may increase by several tenths of Hz, which is consistent with observations. To compare the simulation results with observations, calculations were performed for 95 SFs from the M1.0 – X9.3 class range that occurred between 2002 and 2017. The results of these calculations were compared with experimental data. The calculated changes in the SR frequencies as a function of the X-ray intensity are consistent with the experimental data.