Modelling of the Electron Density and Total Electron Content in the Quiet and Solar X-ray Flare Perturbed Ionospheric D-Region Based on Remote Sensing by VLF/LF Signals

Abstract

Many analyses of the perturbed ionospheric D-region and its influence on the propagation of ground-based and satellite signals are based on data obtained in ionospheric remote sensing by very low/low frequency (VLF/LF) signals. One of the most significant causes of errors in these analyses is the lack of data related to the analysed area and time period preceding the considered perturbation. In this paper, we examine the influence of the estimation of the quiet ionosphere parameters on the determination of the electron density (Ne) and total electron content in the D-region (TECD) during the influence of a solar X-ray flare. We present a new procedure in which parameters describing the quiet ionosphere are calculated based on observations of the analysed area by a VLF/LF signal at the observed time. The developed procedure is an upgrade of the quiet ionospheric D-region (QIonDR) model that allows for a more precise analysis of the D-region intensively perturbed by a solar X-ray flare. The presented procedure is applied to data obtained in ionospheric remote sensing by the DHO signal emitted in Germany and received in Serbia during 30 solar X-ray flares. We give analytical expressions for the dependencies of the analysed parameters on the X-ray flux maximum at the times of the X-ray flux maximum and the most intense D-region perturbation. The results show that the obtained Ne and TECD are larger than in the cases when the usual constant values of the quiet ionosphere parameters are used.

On the altitude profile of lower ionospheric D-region response time delay during solar flares

“…Also, depending upon the strength of the solar flare, the degree of ionisation and sluggish nature of the ionosphere changes. Thomson and Clilverd (2001), McRae and Thomson (2004), Žigman et al (2007), Basak and Chakrabarti (2013), Palit et al (2015), Chakrabarti et al (2018), Hayes et al (2021), Nina (2022) and many others reported a finite and measurable enhancement of D-region ionospheric electron density (N e (t)) during solar flares by studying the sub-ionospheric radio signal propagation effect. By absorbing the incoming solar irradiation during a solar flare, N e (t) starts increasing and reaches at a maximum value (N e, max ).…”

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

“…Despite low electron concentrations in the D region under quiet conditions, the increase in Ne during X‐ray flares is several orders of magnitude (Basak & Chakrabarti, 2013) and, as a result, makes a significant contribution to the change in the total electron content. In (Nina, 2022; Ryakhovskiy et al., 2018), the TEC increment in the D region was estimated using the two‐parameter Wait‐Ferguson model (Ferguson, 1995), which describes the vertical profile of the electron concentration exponentially. The dynamics of this model parameters ( β and h ′) are calculated using experimental variations in the amplitude and phase of VLF signals.…”

Influence of the Neutral Atmosphere Model on the Correctness of Simulation the Electron and Ion Concentrations in the Lower Ionosphere

“…The complex photochemistry at these altitudes is due to the high density of neutral components, which are actively involved in the processes of ionization, collision, attachment, and dissociation (Bekker et al., 2022; Kovacs et al., 2016; Krivolutsky et al., 2015; Turunen et al., 1992; Verronen et al., 2016). This factor and the absence of long series of direct experimental measurements at these heights lead to the fact that this region is still the least studied and most difficult to model (Friedrich et al., 2018; Nina, 2022; Thomson et al., 2022). At the same time, it is important to note that the lower ionosphere has a significant effect on the propagation and absorption of radio waves of various wavelength ranges, especially under conditions of disturbances.…”