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

Vladimir A Srećković,Veljko Vujčić,Ljubinko M Ignjatović,Zoran R Mijić,Desanka M Šulić

doi:10.3390/app112311574

Abstract

Strong radiation from solar X-ray flares can produce increased ionization in the terrestrial D-region and change its structure. Moreover, extreme solar radiation in X-spectral range can create sudden ionospheric disturbances and can consequently affect devices on the terrain as well as signals from satellites and presumably cause numerous uncontrollable catastrophic events. One of the techniques for detection and analysis of solar flares is studying the variations in time of specific spectral lines. The aim of this work is to present our study of solar X-ray flare effects on D-region using very low-frequency radio signal measurements over a long path in parallel with the analysis of X-spectral radiation, and to obtain the atmospheric parameters (sharpness, reflection height, time delay). We introduce a novel modelling approach and give D-region coefficients needed for modelling this medium, as well as a simple expression for electron density of lower ionosphere plasmas. We provide the analysis and software on GitHub.

Highlights

Solar flares (SFs) are giant eruptions on the surface of the Sun [1,2] that release huge amounts of electromagnetic energy over the whole electromagnetic spectrum [3–7]
One of the techniques for detection and analysis of solar flares is studying the variations in time of specific spectral lines
Information on certain solar spectral lines could be of importance in research of solar flares [9,10]

Summary

Introduction

Solar flares (SFs) are giant eruptions on the surface of the Sun [1,2] that release huge amounts of electromagnetic energy over the whole electromagnetic spectrum [3–7]. Levels of photoionization processes in the ionosphere depend on plasma composition along with radiation spectral ranges at specific altitudes [8]. The enhanced Extreme Ultraviolet (EUV) radiation is absorbed at higher terrestrial altitudes ionizing E and F regions of the ionosphere [11]. Lyman-alpha and X-rays penetrate more deeply into the ionosphere, reaching the D-region and causing enhanced ionization and absorption of electromagnetic (EM) waves there [12–14]. Solar flares can be classified into different classes based on their peak emission in the X-ray 0.1–0.8 nm spectral range as B (≥10−7 Wm−2), C (≥10−6 Wm−2), M (≥10−5 Wm−2), and X (≥10−4 Wm−2) classes [15–17]

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Conclusion