Low Ionosphere under Influence of Strong Solar Radiation: Diagnostics and Modeling

Abstract

Solar flares (SFs) and intense radiation can generate additional ionization in the Earth’s atmosphere and affect its structure. These types of solar radiation and activity create sudden ionospheric disturbances (SIDs), affect electronic equipment on the ground along with signals from space, and potentially induce various natural disasters. Focus of this work is on the study of SIDs induced by X-ray SFs using very low frequency (VLF) radio signals in order to predict the impact of SFs on Earth and analyze ionosphere plasmas and its parameters. All data are recorded by VLF BEL stations and the model computation is used to obtain the daytime atmosphere parameters induced by this extreme radiation. The obtained ionospheric parameters are compared with results of other authors. For the first time we analyzed physics of the D-region—during consecutive huge SFs which continuously perturbed this layer for a few hours—in detail. We have developed an empirical model of the D-region plasma density and gave a simple approximative formula for electron density.

Novel Modelling Approach for Obtaining the Parameters of Low Ionosphere under Extreme Radiation in X-Spectral Range

“…In Figure 14, we present the results from this investigation, i.e., paper (using three methods from Sections 2.2.1-2.2.3), which are either simulated, calculated, approximated or the data obtained from literature [16,37,[40][41][42], for electron density N e at reference height as a function of X-ray flux. The area of importance is between the two red lines.…”

“…During SIDs the time profile of electron density follows the solar X-ray flux variation. [16,37,[40][41][42]. Area of importance is between the two red lines.…”

“…The present manuscript offers an extension of the electron-density modeling in the daytime, SF-perturbed D-region of the ionosphere already introduced in [37]. In particular, the extension includes time delays from ionospheric sluggishness in N e modeling, making use of data over a long GC path that ensures enhanced stability of SID-induced variations in phase and amplitude shape.…”

“…Height-dependent coefficients a i (h) can be found in the Github project. Compared to paper [37], here for the first time we introduce ∆t and improve the expression by taking into account the delay time of the ionosphere response, making it more physical.…”

“…Electron-density data (calculated, simulated and approximated) at reference height h = 74 km and maximum of I x flux during occurrence of different class SFs. The data are compared with results from[16,37,[40][41][42]. Area of importance is between the two red lines.…”