Estimate of Lower Ionosphere Ionization during Solar Flares of the X Class According to VLF Observations

Abstract

The results of analysis of measurements of the amplitudes and phases of the GQD (19.6 kHz) andGBZ (22.1 kHz) VLF transmitter signals at the Mikhnevo IGD observatory are presented to estimate of theinfluence of the solar flares X 2.2 and X 1.5 on June 10, 2014 on the electron concentration in the lower ionosphere.The flux of the X-rays in the more rigid spectral ranges of 0.01‒0.3, 0.01‒0.26, and 0.01‒0.22 nmwas calculated based on the measurements of the X-ray emissions at wavelengths of 0.05–0.4 nm and 0.1–0.8 nm at the GOES satellite. That allowed us to find the ionization rate and the emission spectrum rangesthat influenced the electron concentration dynamics most strongly. It is shown that if the duration of the forefrontis substantially less than the characteristic recombination time, the change in the electron concentrationprofile in the lower ionosphere on the flare front is related linearly to the changes in the X-ray emission flux.