Global TEC Variations during the Unique Geospace Storm of May 10–12, 2024

This study provides a detailed comparative analysis of the global spatiotemporal variations of the ionospheric total electron content (TEC) during the extreme geospace storm of May 10–12, 2024. The analysis was conducted using data from 40 global GNSS stations located in Eastern and Western hemispheres near the 68° W and 112° E meridians. This approach allowed for a direct comparison of the ionospheric response in the western and eastern sectors with high spatial and temporal resolution, avoiding the methodological limitations of global smoothing. In the Western Hemisphere, the geospace storm triggered a strong positive ionospheric storm with a TEC enhancement of over 125 TECU at low and mid-latitudes, as well as an intense super-fountain effect that led to a significant expansion of the equatorial ionization anomaly and an equatorial TEC depletion in the trough region of up to 80 TECU. This positive storm was followed by a widespread negative storm, during which the TEC depletion exceeded 60 TECU. In the Eastern Hemisphere, the ionospheric response was characterized by pronounced latitudinal asymmetry, especially during the recovery phase. At latitudes of 15–60° N, a continuous strong negative storm was observed with a TEC depletion of over 40 TECU, whereas at latitudes of 0°–40° S, following an initial brief drop, a steady TEC enhancement was recorded. Furthermore, over the northern mid-latitudes of the Asian sector, localized westward-moving plasma blobs of enhanced electron density were observed, within which TEC values exceeded the background level by more than 50 TECU. The obtained results compellingly emphasize that the global impact of this unique geospace storm was fundamentally asymmetric: the Western Hemisphere experienced the most extreme primary disturbances, while the Eastern Hemisphere demonstrated a structurally distinct response with strong latitudinal divergence.