Peculiar Nighttime Ionospheric Enhancements Over the Asian Sector During the May 2024 Superstorm

Abstract

This study reports a peculiar nighttime ionospheric enhancement in the total electron content (TEC) from the geostationary (GEO) satellites in response to the geomagnetic superstorm of May 2024. The enhancements occurred at low to mid-latitudes during the storm's recovery phase on 11–12 May, with the TEC values almost twice as high as the quiet ones. Surprisingly, the nighttime ionospheric enhancements sub-rotated westward with a speed of ∼130.5 m/s. The nighttime TEC enhancements lasted ∼5–7 hr for a given location and persisted over half a day over wide longitude ranges. Meanwhile, ionosonde data from two equatorial ionization anomaly (EIA) stations showed a higher peak height of the F2 layer, and a significant double-crest EIA structure was observed by both GEO TECs and in situ electron densities from China Seismo-Electromagnetic Satellite during this period of interest, indicating a possible contribution from disturbance electric fields producing nighttime eastward equatorial electric fields. Nevertheless, it remains a mystery whether the nighttime TEC enhancement and its movement were associated with the wind disturbance dynamo.