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

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

  • Автор: Bekker S.Z., Ryakhovsky I.A.
  • Издательство: Journal of Geophysical Research Space Physics

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. A technique for estimating the redistribution of the electron concentration in the ionosphere during solar flares is presented It was found that the contribution of the D region to the TEC change varied from 7% to 23% during the flares in September 2017 A functional dependency of the D region contribution to the TEC change on the fraction of X‐rays in the flare spectrum is obtained A technique for estimating the redistribution of the electron concentration in the ionosphere during solar flares is presented It was found that the contribution of the D region to the TEC change varied from 7% to 23% during the flares in September 2017 A functional dependency of the D region contribution to the TEC change on the fraction of X‐rays in the flare spectrum is obtained Changes in solar radiation fluxes are observed in a wide range of wavelengths during solar flares. The variations of total electron content in the ionosphere occurs due to an increase in radiation in the UV and X‐ray wavelength ranges. The main increase in ionization caused by flares occurs in the F region (h > 120 km), so the electron concentration increment in the lower part of the ionosphere (h < 90 km) is often neglected. The existing experimental measurement methods do not allow us to estimate the redistribution of the electron concentration in the ionosphere during disturbances; therefore, to estimate the contribution of the lower ionosphere to the total electron content during flares, we used GNSS data and theoretical plasma‐chemical model of the D region. In this work, it is shown that the contribution of the D region to the change of the total electron content can reach 23% during X‐ray flares.

Bekker, S. Z., & Ryakhovsky, I. A. (2024). Estimation of the contribution of the ionospheric D region to the TEC value during a series of solar flares in September 2017 // Journal of Geophysical Research: Space Physics, 129, e2024JA032577. 

https://doi.org/10.1029/2024JA032577