Speaker
Description
Severe geomagnetic storms have a significant impact on ionospheric and geomagnetic dynamics, particularly in equatorial regions such as Thailand. These disturbances often manifest as modifications to the Equatorial Ionization Anomaly (EIA) and the development or suppression of Equatorial Plasma Bubbles (EPBs). These effects are primarily driven by storm-time electric fields and associated changes in ionospheric currents, which result from interactions between the energetic solar wind and Earth's magnetosphere, through the polar and higher latitude regions.
The intense geomagnetic storm that occurred between 10–12 May 2024, during the solar maximum of Solar Cycle 25, had a profound effect on the characteristics of the equatorial ionosphere and geomagnetic field [1–2]. This study investigates the storm’s impact using observations from the ionospheric monitoring network around Thailand, jointly operated by King Mongkut’s Institute of Technology Ladkrabang (KMITL), the Space Technology Research Center, Geo-Informatics and Space Technology Development Agency (GISTDA), and the National Institute of Information and Communications Technology (NICT). We analyze data from GNSS receivers, magnetometers, and ionosondes to assess the influences of storm-time interplanetary magnetic field (IMF) and interplanetary electric field (IEF) variations on local equatorial magnetic fields and ionospheric parameters.
We utilize Singular Spectrum Analysis (SSA) to decompose ionospheric Total Electron Content (TEC) and geomagnetic variations into elementary components. Using Pearson correlation analysis, we evaluate correlations between these SSA-reconstructed components and interplanetary geophysical parameters, as well as other ionospheric parameters such as the critical frequency of the F2 layer (foF2). Variations in correlation coefficients between the reconstructed field components and interplanetary parameters help to distinguish the sources and effects of these disturbances. The results clearly reveal distinct contributions to geomagnetic field variations from both interplanetary and ionospheric current systems. We also compare the impacts of the two most intense geomagnetic storms in Solar Cycles 24 and 25, namely the storms of March 2015 [3], and May 2024. The findings indicate that storm-time electric fields, such as prompt penetration electric fields (PPEF) and disturbance dynamo electric fields (DDEF), strongly influenced the equatorial electric field, which is indirectly inferred from geomagnetic field variations, leading to significant fluctuations in TEC.
Acknowledgement
This work is partially supported by King Mongkut’s Institute of Technology Ladkrabang and the NSRF via the Program Management Unit for the Human Resources and Institutional Development, Research and Innovation (Grant no. B41G680028).
References
[1] Myint, L.M., Perwitasari, S., Nishioka, M., Saito, S., Kaewthongrach, R., Supnithi, P. (2025). Analysis of ionospheric and geomagnetic field changes in Thailand during the May 2024 geomagnetic storm. Advances in Space Research. https://doi.org/10.1016/j.asr.2025.01.071
[2] Karan, D.K., Martinis, C.R., Daniell, R.E., Eastes, R.W., Wang, W., McClintock, W.E., et al. (2024). GOLD observations of the merging of the southern crest of the equatorial ionization anomaly and aurora during the 10 and 11 May 2024 Mother’s Day super geomagnetic storm. Geophysical Research Letters, 51(15), e2024GL110632. https://doi.org/10.1029/2024GL110632
[3] Wu, C.C., Liou, K., Lepping, R.P., et al. (2016). The first super geomagnetic storm of Solar Cycle 24: “The St. Patrick’s Day event (17 March 2015)”. Earth, Planets and Space, 68, 151. https://doi.org/10.1186/s40623-016-0525-y
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