Abstract The present study investigates the ionospheric impacts of three intense geomagnetic storms that occurred on 10–11 May 2024 (Sym-H: –518 nT), 23–24 April 2023 (Sym-H: –233 nT), and 23–24 March 2023 (Sym-H: –170 nT) during the ascending phase of solar cycle 25. The storm-induced ionospheric perturbations analysis over dip equatorial station in Thanjavur, India (geomagnetic: 2.49°N, 152.26°E) has been done by using GPS derived TEC data. Results reveal that the intensity and onset timing of storm influences magnitude and spatial extent of ionospheric disturbances. Interestingly, both positive and negative ionospheric impacts have been observed during different phases of storms. The results are also significantly larger ionospheric responses to those storms that initiated during local midnight hours, as observed during the event that occurred in May 2024. However, the modest positive and negative ionospheric responses detected during the different phases of storms could be the result of prompt penetration of electric fields (PPEFs) and disturbance dynamo electric fields (DDEFs). Thermospheric alterations, driven by Joule heating and circulation changes from high-latitudes toward equator, thereby modulating overall ionization rates. To the best of our knowledge, this study provides one of a few comparative ground-based GPS-TEC analyses of these three intense geomagnetic storms of different origin over the Indian near-geomagnetic-equatorial sector, emphasizing how storm onset local time and storm nature influence the sign, magnitude, and timing of ionospheric response. These findings may enhance understanding of how equatorial ionosphere reacts to intense geomagnetic disturbances, thereby supporting efforts to develop robust space-weather forecasting and modelling systems. Research highlights <UnorderedList Mark="Bullet"> <ItemContent> Comparative analysis of three intense storms at equatorial region demonstrates that variations in interplanetary drivers and IMF-Bz/IEF-Ey fluctuations govern the transition between positive and negative storm phases through competing PPEF and DDEF effects. </ItemContent> <ItemContent> Study reveals that geomagnetic storm onset local-time critically determines the magnitude and polarity of ionospheric disturbances. Storm commencing during post-sunset hours produced stronger TEC deviations due to enhanced PPEFs and PRE. </ItemContent> <ItemContent> Study provides one of the few ground-based GPS-TEC assessments of multiple intense storms of different origins in Indian near-equatorial sector, establishing how thermospheric composition changes and equatorward neutral wind propagation modulate storm-time TEC behaviour. </ItemContent> </UnorderedList>

Investigation of ionospheric impact of different nature of geomagnetic storms over the near geomagnetic equatorial location, Thanjavur (2.49°N, 152.26°E), India

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发表日期：

2026年4月9日

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Gaurav Verma,
Vaishali,
Neha,
James A Baskaradas,
Rupesh M Das

摘要

Abstract

The present study investigates the ionospheric impacts of three intense geomagnetic storms that occurred on 10–11 May 2024 (Sym-H: –518 nT), 23–24 April 2023 (Sym-H: –233 nT), and 23–24 March 2023 (Sym-H: –170 nT) during the ascending phase of solar cycle 25. The storm-induced ionospheric perturbations analysis over dip equatorial station in Thanjavur, India (geomagnetic: 2.49°N, 152.26°E) has been done by using GPS derived TEC data. Results reveal that the intensity and onset timing of storm influences magnitude and spatial extent of ionospheric disturbances. Interestingly, both positive and negative ionospheric impacts have been observed during different phases of storms. The results are also significantly larger ionospheric responses to those storms that initiated during local midnight hours, as observed during the event that occurred in May 2024. However, the modest positive and negative ionospheric responses detected during the different phases of storms could be the result of prompt penetration of electric fields (PPEFs) and disturbance dynamo electric fields (DDEFs). Thermospheric alterations, driven by Joule heating and circulation changes from high-latitudes toward equator, thereby modulating overall ionization rates. To the best of our knowledge, this study provides one of a few comparative ground-based GPS-TEC analyses of these three intense geomagnetic storms of different origin over the Indian near-geomagnetic-equatorial sector, emphasizing how storm onset local time and storm nature influence the sign, magnitude, and timing of ionospheric response. These findings may enhance understanding of how equatorial ionosphere reacts to intense geomagnetic disturbances, thereby supporting efforts to develop robust space-weather forecasting and modelling systems.

Research highlights

Comparative analysis of three intense storms at equatorial region demonstrates that variations in interplanetary drivers and IMF-Bz/IEF-Ey fluctuations govern the transition between positive and negative storm phases through competing PPEF and DDEF effects.

Study reveals that geomagnetic storm onset local-time critically determines the magnitude and polarity of ionospheric disturbances. Storm commencing during post-sunset hours produced stronger TEC deviations due to enhanced PPEFs and PRE.

Study provides one of the few ground-based GPS-TEC assessments of multiple intense storms of different origins in Indian near-equatorial sector, establishing how thermospheric composition changes and equatorward neutral wind propagation modulate storm-time TEC behaviour.