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Study of intense space weather effects of May 2024 on the ionosphere over the Indian region using IRNSS/NavIC.

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Title: Study of intense space weather effects of May 2024 on the ionosphere over the Indian region using IRNSS/NavIC.
Authors: Chougule, Susmita1 (AUTHOR), Shetti, Dadaso1 (AUTHOR) shettidj2002@yahoo.co.in, Fleury, R.2 (AUTHOR), Venkatesh, K.3 (AUTHOR), Chougule, Prajakta1 (AUTHOR)
Source: Advances in Space Research. Dec2025, Vol. 76 Issue 12, p7471-7488. 18p.
Subjects: Ionosphere, Magnetic storms, Solar flares, Space environment, Global Positioning System, Total electron content (Atmosphere)
Geographic Terms: India, South Asia
Abstract: In May 2024, a severe geomagnetic storm the most intense since 2003, with a Dst index reaching –412 nT was triggered by the active sunspot region AR13664, which produced multiple X-class solar flares and coronal mass ejections (CMEs). This study investigates the combined effects of the geomagnetic storm and solar flares over the South Asian region, particularly India and Sri Lanka, using data from the International GNSS Service (IGS) stations and the Indian Regional Navigation Satellite System (IRNSS/NavIC) during May 9–13, 2024. We analyzed Total Electron Content (TEC), the scintillation index (S4), and the Rate of TEC Index (ROTI), along with electric field estimations from the PPEFM model and neutral composition data (O/N 2) from GUVI/TIMED. A significant TEC depletion was observed during the main phase of the storm across the South Asian region, attributed to westward electric fields suppressing the upward E × B drift. TEC enhancements during the early hours of May 11 at all stations except IITK were consistent with the highly unstable and rapidly changing polarity of the PPEF, along with the influence of westward DDEF and strong equatorward meridional winds. No significant S4 (IRNSS) or strong ROTI activity was recorded during the main and recovery phases, likely due to the prevalence of westward or weak eastward electric fields combined with westward DDEF. Short-lived TEC enhancements with stronger responses near local noon were observed for the X3.9-class flare at all stations except IITK. The initial TEC enhancement observed on May 11 is attributed to the X5.8-class flare, with its higher magnitude primarily influenced by the geomagnetic storm. In contrast, the X1.5-class flare showed no TEC enhancement over any station, likely due to the dominance of DDEF over ionospheric dynamics. These results demonstrate that the combined effects of solar flares and storm-driven electrodynamic processes can lead to distinct ionospheric responses across different latitudes in South Asia. [ABSTRACT FROM AUTHOR]
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Abstract:In May 2024, a severe geomagnetic storm the most intense since 2003, with a Dst index reaching –412 nT was triggered by the active sunspot region AR13664, which produced multiple X-class solar flares and coronal mass ejections (CMEs). This study investigates the combined effects of the geomagnetic storm and solar flares over the South Asian region, particularly India and Sri Lanka, using data from the International GNSS Service (IGS) stations and the Indian Regional Navigation Satellite System (IRNSS/NavIC) during May 9–13, 2024. We analyzed Total Electron Content (TEC), the scintillation index (S4), and the Rate of TEC Index (ROTI), along with electric field estimations from the PPEFM model and neutral composition data (O/N 2) from GUVI/TIMED. A significant TEC depletion was observed during the main phase of the storm across the South Asian region, attributed to westward electric fields suppressing the upward E × B drift. TEC enhancements during the early hours of May 11 at all stations except IITK were consistent with the highly unstable and rapidly changing polarity of the PPEF, along with the influence of westward DDEF and strong equatorward meridional winds. No significant S4 (IRNSS) or strong ROTI activity was recorded during the main and recovery phases, likely due to the prevalence of westward or weak eastward electric fields combined with westward DDEF. Short-lived TEC enhancements with stronger responses near local noon were observed for the X3.9-class flare at all stations except IITK. The initial TEC enhancement observed on May 11 is attributed to the X5.8-class flare, with its higher magnitude primarily influenced by the geomagnetic storm. In contrast, the X1.5-class flare showed no TEC enhancement over any station, likely due to the dominance of DDEF over ionospheric dynamics. These results demonstrate that the combined effects of solar flares and storm-driven electrodynamic processes can lead to distinct ionospheric responses across different latitudes in South Asia. [ABSTRACT FROM AUTHOR]
ISSN:02731177
DOI:10.1016/j.asr.2025.09.045