Estimation of the Contribution of the Ionospheric D Region to the TEC Value During a Series of Solar Flares in September 2017

Abstract

The paper presents the results of a numerical assessment of the contribution of the ionospheric D region to the total electron content during six powerful X‐ray flares that occurred in September 2017. The calculation of the electron concentration in the lower ionosphere was carried out using a plasma‐chemical model of the ionospheric D region. This model was verified using the data of ground‐based radiophysical measurements in the VLF (very low frequency) range and data of the incoherent scattering radar. To calculate the ionization rate at the D region heights, we used real data on the radiation flux measured by the GOES and SDO satellites during the considered flares. The total electron content was estimated using GNSS data. As a result of the analysis, it was found that the contribution of the lower ionosphere to the TEC change varied from 7% to 23% for flares with different spectra. A functional dependency has been obtained that can be used to estimate the contribution of the D region to the TEC increment depending on the spectrum of the flare.