D- and F-Region Ionospheric Response to the Severe Geomagnetic Storm of April 2023
2025
Arnab Sen | Sujay Pal | Bakul Das | Sushanta K. Mondal
This study investigates the impact on the Earth&rsquo:s ionosphere of a severe geomagnetic storm (Dst :&sim: :&minus:212 nT) that began on 23 April 2023 at around 17:37 UT according to very low-frequency (VLF, 3&ndash:30 kHz) or low-frequency (LF, 30&ndash:300 kHz) radio signals and ionosonde data. We analyze VLF/LF signals received by SuperSID monitors located in mid-latitude (Europe) and low-latitude (South America, Colombia) areas across nine different propagation paths in the Northern Hemisphere. Mid-latitude regions exhibited a daytime amplitude perturbation, mostly an increase, by &sim:3&ndash:5 dB during the storm period, with a subsequent recovery after 7&ndash:8 days post April 23. In contrast, signals received in low-latitude regions (UTP, Colombia) did not show significant variation during the storm-disturbed days. We also observe that the 3-hour average of foF2 data declined by up to 3 MHz on April 23 and April 24 at the European Digisonde stations. However, no significant variation in foF2 was observed at the low-latitude Digisonde stations in Brazil. Both the VLF and ionosonde data exhibited anomalies during the storm period in the European regions, confirming that both D- and F-region ionospheric perturbation was caused by the severe geomagnetic storm.
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