Estimation of the impact of solar flare spectra on the Earth’s ionosphere using the GAIA model
The rapid increase in X-ray and extreme ultraviolet (EUV) emissions owing to solar flares enhances ionization in the ionosphere, increasing radio wave attenuation. Among these phenomena, the shortwave communication disturbance caused by the increased electron density in the ionospheric D region is k...
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EDP Sciences
2025-01-01
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| Series: | Journal of Space Weather and Space Climate |
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| Online Access: | https://www.swsc-journal.org/articles/swsc/full_html/2025/01/swsc240007/swsc240007.html |
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| author | Kitajima Shinnosuke Watanabe Kyoko Jin Hidekatsu Tao Chihiro Nishioka Michi |
| author_facet | Kitajima Shinnosuke Watanabe Kyoko Jin Hidekatsu Tao Chihiro Nishioka Michi |
| author_sort | Kitajima Shinnosuke |
| collection | DOAJ |
| description | The rapid increase in X-ray and extreme ultraviolet (EUV) emissions owing to solar flares enhances ionization in the ionosphere, increasing radio wave attenuation. Among these phenomena, the shortwave communication disturbance caused by the increased electron density in the ionospheric D region is known as the shortwave fadeout (SWF). We investigated the relationship between SWF’s magnitude and solar flare emission, and evaluated the electron density variation in the ionospheric D region associated with flare. We defined the minimum frequency (fmin) observed in Japan’s ionograms as the SWF’s magnitude. We analyzed ionosonde data for 38 SWF events observed during daytime in Japan between May 2010 and May 2014. To investigate the relationship between flares and SWF, we compared the observed X-ray and EUV emissions during flares with the dfmin (background subtracted fmin). X-ray (0.1–0.8 nm) and EUV (11–14 nm) emissions correlate with dfmin. Then, using the GAIA model, a numerical model that treats the entire Earth’s atmosphere, we investigated the effect of the X-ray and EUV solar flare emissions on the ionosphere, which affects the SWF. The results showed that the main ionization source in the ionospheric D region was X-ray emission, and shortwaves were attenuated by ∼90%. In contrast, in the ionospheric E and F regions, the primary ionization source was EUV emission, with only ∼10% shortwave attenuation. Finally, we estimated the fmin values and blackout (total fadeout of the ionospheric echo observed in ionograms) and compared the simulated and observed fmin values. The hit rate of blackouts was 35% when we only used the GAIA calculations. Therefore, we estimated fmin using the electron density variation in the ionospheric D region corresponding to X-ray solar emission. As a result, the hit rate of the blackout was 68%, and the linear correlation coefficient between the simulated and observed fmin values was 0.85. The estimated magnitude of the SWF was improved by incorporating the effects of X-ray emissions into the ionospheric D region of GAIA. We are the first to implement a method for evaluating the electron density in the ionospheric D region using the fmin value. |
| format | Article |
| id | doaj-art-d4c8b0a763414f5db11020dd86279028 |
| institution | OA Journals |
| issn | 2115-7251 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | EDP Sciences |
| record_format | Article |
| series | Journal of Space Weather and Space Climate |
| spelling | doaj-art-d4c8b0a763414f5db11020dd862790282025-08-20T01:51:41ZengEDP SciencesJournal of Space Weather and Space Climate2115-72512025-01-01151010.1051/swsc/2025008swsc240007Estimation of the impact of solar flare spectra on the Earth’s ionosphere using the GAIA modelKitajima Shinnosuke0Watanabe Kyoko1https://orcid.org/0000-0003-0321-7881Jin Hidekatsu2Tao Chihiro3Nishioka Michi4National Defense Academy of Japan (NDA)National Defense Academy of Japan (NDA)National Institute of Information and Communications Technology (NICT)National Institute of Information and Communications Technology (NICT)National Institute of Information and Communications Technology (NICT)The rapid increase in X-ray and extreme ultraviolet (EUV) emissions owing to solar flares enhances ionization in the ionosphere, increasing radio wave attenuation. Among these phenomena, the shortwave communication disturbance caused by the increased electron density in the ionospheric D region is known as the shortwave fadeout (SWF). We investigated the relationship between SWF’s magnitude and solar flare emission, and evaluated the electron density variation in the ionospheric D region associated with flare. We defined the minimum frequency (fmin) observed in Japan’s ionograms as the SWF’s magnitude. We analyzed ionosonde data for 38 SWF events observed during daytime in Japan between May 2010 and May 2014. To investigate the relationship between flares and SWF, we compared the observed X-ray and EUV emissions during flares with the dfmin (background subtracted fmin). X-ray (0.1–0.8 nm) and EUV (11–14 nm) emissions correlate with dfmin. Then, using the GAIA model, a numerical model that treats the entire Earth’s atmosphere, we investigated the effect of the X-ray and EUV solar flare emissions on the ionosphere, which affects the SWF. The results showed that the main ionization source in the ionospheric D region was X-ray emission, and shortwaves were attenuated by ∼90%. In contrast, in the ionospheric E and F regions, the primary ionization source was EUV emission, with only ∼10% shortwave attenuation. Finally, we estimated the fmin values and blackout (total fadeout of the ionospheric echo observed in ionograms) and compared the simulated and observed fmin values. The hit rate of blackouts was 35% when we only used the GAIA calculations. Therefore, we estimated fmin using the electron density variation in the ionospheric D region corresponding to X-ray solar emission. As a result, the hit rate of the blackout was 68%, and the linear correlation coefficient between the simulated and observed fmin values was 0.85. The estimated magnitude of the SWF was improved by incorporating the effects of X-ray emissions into the ionospheric D region of GAIA. We are the first to implement a method for evaluating the electron density in the ionospheric D region using the fmin value.https://www.swsc-journal.org/articles/swsc/full_html/2025/01/swsc240007/swsc240007.htmlshortwave fadeout (swf)dellinger phenomenonsolar flareionospherex-ray emissioneuv emissionspace weather |
| spellingShingle | Kitajima Shinnosuke Watanabe Kyoko Jin Hidekatsu Tao Chihiro Nishioka Michi Estimation of the impact of solar flare spectra on the Earth’s ionosphere using the GAIA model Journal of Space Weather and Space Climate shortwave fadeout (swf) dellinger phenomenon solar flare ionosphere x-ray emission euv emission space weather |
| title | Estimation of the impact of solar flare spectra on the Earth’s ionosphere using the GAIA model |
| title_full | Estimation of the impact of solar flare spectra on the Earth’s ionosphere using the GAIA model |
| title_fullStr | Estimation of the impact of solar flare spectra on the Earth’s ionosphere using the GAIA model |
| title_full_unstemmed | Estimation of the impact of solar flare spectra on the Earth’s ionosphere using the GAIA model |
| title_short | Estimation of the impact of solar flare spectra on the Earth’s ionosphere using the GAIA model |
| title_sort | estimation of the impact of solar flare spectra on the earth s ionosphere using the gaia model |
| topic | shortwave fadeout (swf) dellinger phenomenon solar flare ionosphere x-ray emission euv emission space weather |
| url | https://www.swsc-journal.org/articles/swsc/full_html/2025/01/swsc240007/swsc240007.html |
| work_keys_str_mv | AT kitajimashinnosuke estimationoftheimpactofsolarflarespectraontheearthsionosphereusingthegaiamodel AT watanabekyoko estimationoftheimpactofsolarflarespectraontheearthsionosphereusingthegaiamodel AT jinhidekatsu estimationoftheimpactofsolarflarespectraontheearthsionosphereusingthegaiamodel AT taochihiro estimationoftheimpactofsolarflarespectraontheearthsionosphereusingthegaiamodel AT nishiokamichi estimationoftheimpactofsolarflarespectraontheearthsionosphereusingthegaiamodel |