Data-based optimization of a simple shortwave fadeout absorption model

Fiori, R. A. D.; Chakraborty, Shibaji; Nikitina, Lidia

doi:10.1016/j.jastp.2022.105843

Cited by 6 publications

(4 citation statements)

References 31 publications

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“…Shortly following a solar flare (∼8 min), Extreme Ultra‐Violet and X‐ray radiation enhance D‐region ionization, causing significant radio‐wave absorption, the levels of which depend on operating frequency, solar‐zenith angle, and the magnitude of the flare (Davies, 1990). SWF having both high occurrence rate per solar cycle (Fiori, Kumar, et al., 2022) and large area‐of‐effect implies that modeling is of great importance to HF communication and navigation systems (Chakraborty et al., 2021; Fiori, Chakraborty, & Nikitina, 2022).…”

Section: Introductionmentioning

confidence: 99%

Use of Terrestrial High Frequency Signals in Riometer Data to Explore the Size of D‐Region Electron Density Enhancements

Ghaly,

Spanswick,

Gillies

et al. 2024

JGR Space Physics

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This paper presents the first observations from the prototype Space Weather Adaptive Network (SWAN) riometers, which are capable of simultaneous measurements of narrow‐band terrestrial signal power and Cosmic Noise Absorption (CNA). We describe a methodology by which we can use coincident CNA and loss of known skywave‐mode, High Frequency (HF) signals to estimate a minimum size (geographic extent) of D‐region electron density enhancements. We demonstrate our technique with an example event. This methodology and early results provide a pathfinder for a continent‐wide array of SWAN instruments which would be capable of utilizing multiple intersecting terrestrial HF ray paths to reconstruct the size of D‐region electron density enhancements at the time of initial HF signal loss.

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Section: Introductionmentioning

confidence: 99%

Use of Terrestrial High Frequency Signals in Riometer Data to Explore the Size of D‐Region Electron Density Enhancements

Ghaly,

Spanswick,

Gillies

et al. 2024

JGR Space Physics

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“…In the ionosphere, radio wave absorption is caused by the collision of electrons with other particles (Chen & Fejer, 1975). When an electron collides with neutrals or ions (primarily neutrals) under the influence of the field of an incident radio‐wave, energy is transferred from radio‐wave to heat energy and finally transferred to ions and other electrons via momentum transfer equation which is governed by the conservation of momentum, and thus High Frequency (HF) radio waves experience absorption (Chakraborty et al., 2021; Fiori et al., 2022; Mitra, 1974). The ionospheric HF absorption can significantly influence the strength of the received signal.…”

Section: Introductionmentioning

confidence: 99%

Variation of Ionospheric Shortwave Absorption of the Extraordinary Wave

Jiang,

Li,

Guo

et al. 2023

JGR Space Physics

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In this study, associating with the A‐H formulation, we have developed a comprehensive ionospheric absorption model by incorporating the latest version of geomagnetic model, the atmospheric and ionospheric model as the background. Based on the absorption model, the ionospheric stratification theory is utilized to explore the trend of the total absorption for extraordinary (X) wave with frequency and elevation angle. We found that the factor of local time has a greater impact on the trend of total absorption variation than other factors—solar activity, season, and latitude, attributing to the variation of electron collision frequency. During the two different local times (daytime and night), the trends of the total absorption have distinct differences. In the daytime, it is worth noting that the reflection heights and the peaks of the absorption coefficient both mainly occur in Layers D and E. Therefore, the non‐deviative absorption dominates the variation of the total absorption. On the other hand, the occurrence of Pedersen ray results in inflexion points arising in the curves of absorption versus frequency or elevation angle. Another interesting phenomenon is the dominant role of deviative absorption at night. At night, the reflection heights mainly occur in Layer F, and the absorption coefficient of Layer F begins to exceed the peak levels of Layers D and E when the frequency or elevation angle is larger than certain values. Hence, the total absorption will grow as a result of the increase in deviative absorption with the increase in reflection height and absorption coefficient.

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“…The phenomena caused by the sudden ionization of the Earth's upper atmosphere by X-rays and EUV emitted from solar flares are widely known as sudden ionospheric disturbances (SIDs) (Davies 1990;Donnely 1969;Mitra 1974). SIDs are sudden disturbances of the ionosphere and are a superset of events, which consists of Dellinger effect (Dellinger 1937), short-wave fadeout (SWF) (e.g., Chakraborty et al 2018Chakraborty et al , 2019Chakraborty et al , 2022Fiori et al 2018Fiori et al , 2022, sudden frequency and phase deviation (SFD/SPD) (Chakraborty et al 2018;Watanabe and Nishitani 2013), solar flare effects (SFEs) (e.g., Curto et al 2018), and sudden increase in total electron content (SITEC) (e.g., Tsugawa et al 2006;Zhang et al 2011). In 1957, the International Geophysical Year, much was offered from around the world on SIDs, and research in this field began to advance dramatically (Curto 2020).…”

Section: Introductionmentioning

confidence: 99%

Statistical analysis for EUV dynamic spectra and their impact on the ionosphere during solar flares

Nishimoto

Watanabe

Jin

et al. 2023

Earth Planets Space

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The X-rays and extreme ultraviolet (EUV) emitted during solar flares can rapidly change the physical composition of Earth’s ionosphere, causing space weather phenomena. It is important to develop an accurate understanding of solar flare emission spectra to understand how it affects the ionosphere. We reproduced the entire solar flare emission spectrum using an empirical model and physics-based model, and input it into the Earth’s atmospheric model, GAIA to calculate the total electron content (TEC) enhancement due to solar flare emission. We compared the statistics of nine solar flare events and calculated the TEC enhancements with the corresponding observed data. The model used in this study was able to estimate the TEC enhancement due to solar flare emission with a correlation coefficient greater than 0.9. The results of this study indicate that the TEC enhancement due to solar flare emission is determined by soft X-ray and EUV emission with wavelengths shorter than 35 nm. The TEC enhancement is found to be largely due to the change in the soft X-ray emission and EUV line emissions with wavelengths, such as Fe XVII 10.08 nm, Fe XIX 10.85 nm and He II 30.38 nm. Graphical Abstract

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Data-based optimization of a simple shortwave fadeout absorption model

Cited by 6 publications

References 31 publications

Use of Terrestrial High Frequency Signals in Riometer Data to Explore the Size of D‐Region Electron Density Enhancements

Use of Terrestrial High Frequency Signals in Riometer Data to Explore the Size of D‐Region Electron Density Enhancements

Variation of Ionospheric Shortwave Absorption of the Extraordinary Wave

Statistical analysis for EUV dynamic spectra and their impact on the ionosphere during solar flares

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