Ionospheric Response to the 10 May 2024 Geomagnetic Storm as Observed in GNSS Radio Occultation Electron Density

We investigate the spatiotemporal and altitude variations in ionospheric F-region electron density in response to the 10 May 2024 superstorm, the most significant geomagnetic disturbance in two decades. The unprecedented sampling by ∼12,000 electron density profiles each day from the COSMIC-2, Spire and FengYun-3 radio occultation observations provided a nearly global and full local time coverage of this event. During the main phase of the storm, F-region (200–500 km in altitude) electron density decreased globally, with peak electron density height increasing during daytime and decreasing at nighttime in low latitude. Concurrently, topside electron density increased in the low-latitude during the daytime. Additionally, the broadening of the equatorial ionospheric anomaly (EIA) width provides strong evidence of the storm-induced electric field's effect during the storm main phase. Subsequently, the EIA crests merged and remained for about 21 hr during the end of main phase and the recovery phase, suggesting a possible storm-induced equatorial wind impact on the ionosphere. Furthermore, electron density maps reveal hemispheric asymmetry in the storm response. Electron density decreases more effectively in the northern hemisphere than in the southern hemisphere, indicating a significant role of seasonal global circulation during the geomagnetic storm.