In this paper our attention is focused on relations between radio signal propagation characteristics and temperature changes in D-region after solar X-flare occurrence. We present temperature dependencies of electron plasma frequency, the parameter that describes medium conditions for propagation of an electromagnetic wave, and the refractive index which describes how this wave propagates. As an example for quantitative calculations based on obtained theoretical equations we choose the reaction of the D-region to the solar X-flare occurred on May 5 th , 2010. The ionospheric modelling is based on the experimental data obtained by low ionosphere observations using very low frequency radio signal.

Original scientific paper https://doi.org/10.2298/TSCI190501313NIn this paper we present an analysis of parameters describing the effective recombination processes in the upper ionospheric D-region in the period of its additional heating by the X-radiation emitted during a solar X-ray flare. We present a procedure for calculation of the effective recombination coefficient and electron loss rate in the period when the X-radiation flux detected by the GOES satellite in the wavelength domain between 0.1 and 0.8 nm increases. The developed procedure is based on observational data obtained in the low ionospheric monitoring by the very low/low frequency radio waves and it is related to the considered area and time period. The obtained expressions are applied to data for the very low frequency signal emitted in Germany and recorded in Serbia during the solar X-ray flare detected by the GOES-14 satellite on May 5, 2010.