Abstract Capturing global ionospheric response during extreme geomagnetic storms remains a major observational challenge. During 10–11 May, 2024 superstorm, we investigate the height‐dependent response of the F‐region using multi‐constellation GNSS‐POD limb‐sounding measurements from COSMIC‐2, Spire, PlanetiQ, and FengYun‐3 satellites. Approximately 12,000 vertical electron density (Ne) profiles per day are retrieved using an optimal‐estimation inversion, resolving both topside and bottomside structures. In parallel, we derive global vertical total electron content (vTEC) from 18,000 GNSS‐RO links per day, providing uniform sampling across land and ocean. During the storm's main phase, Ne profiles reveal dramatic F2‐layer uplifts exceeding 450 km, with localized peaks above 500 km and concurrent reductions in Ne near 300 km, consistent with storm‐time drifts. The equatorial ionization anomaly (EIA) expanded poleward, developed into a pronounced super‐fountain structure, and migrated westward with local time. This evolution, along with the merging of EIA crests with the expanding auroral oval, highlights strong coupling between low‐ and high‐latitude regions. As the storm entered the recovery phase, Ne between 250 and 450 km showed 55%–70% daytime depletions. At 350 km, Ne losses were up to three times larger in the summer hemisphere compared to the winter hemisphere, whereas at 250 km the winter hemisphere exhibited nearly double the depletion, indicating a reversal of interhemispheric asymmetry. Recovery was strongly altitude‐ and diurnal‐dependent, faster at low altitudes during daytime but slower at night in the northern hemisphere. We also incorporated ground‐based TEC measurements to track storm‐time high‐latitude irregularities and auroral boundary motion. We identify equatorward boundary migration to 33N, providing an effective tracer of auroral morphology during both day and night, complementing space‐based Ne signatures. Results demonstrate that the integration of multi‐satellite and ground‐based observations provides benchmarks for ionosphere‐thermosphere and space‐weather monitoring, modeling, and forecasting.
Swarnalingam et al. (Thu,) studied this question.