Electric Field and Thermospheric Control of Recovery‐Phase TEC and Ionospheric Irregularities Over China During the May and October 2024 G5 Superstorms
Chaoqian Xu, Jintao Wang, Jun Tang, Mingxian HuAbstract
The ionospheric recovery responses to two G5 geomagnetic storms over China in May and October 2024 were compared using GNSS‐derived total electron content (TEC), detrended TEC, the rate of TEC index (ROTI), magnetometer data, and GUVI/TIMED O/N 2 observations. The results show that the May recovery phase was dominated by widespread and persistent negative TEC anomalies, with low‐latitude depletion reaching approximately 60 TECU. In contrast, the October event exhibited a pronounced latitudinal structure, including a C‐shaped positive enhancement at mid‐latitudes and low‐latitude depletion of approximately 50 TECU. The elevated O/N 2 ratio may have favored the mid‐latitude enhancement. Although substantial low‐latitude TEC depletion occurred on both May 11 and October 11, no pronounced ROTI enhancement was observed in October, suggesting that the depletion was mainly associated with weakened electrodynamic forcing, contraction of the EIA, and reduced electron content in the upper ionosphere. Six groups of large‐scale traveling ionospheric disturbances (LSTIDs) and two types of ionospheric irregularities were identified in May, compared with three LSTID groups and one type of brief, localized irregularity in October. These differences suggest that high‐latitude energy input, low‐latitude electrodynamics, and thermospheric composition jointly controlled the contrasting ionospheric recovery responses.