Interplay of Gravity Waves and Disturbance Electric Fields to the Abnormal Ionospheric Variations During the 11 May 2024 Superstorm

Abstract

The strongest geomagnetic storm in the preceding two decades occurred in May 2024. Over these years, ground-based observational capabilities have been significantly enhanced to monitor the ionospheric weather. Notably, the newly established Sanya incoherent scatter radar (SYISR) (Yue, Wan, Ning, & Jin, 2022, https://doi.org/10.1038/s41550-022-01684-1), one of the critical infrastructures of the Chinese “Meridian Project,” provides multiple parameter measurements in the upper atmosphere at low latitudes over Asian longitudies. Unique ionospheric changes on superstorm day 11 May were first recorded by the SYISR experiments and the geostationary satellite (GEO) total electron content (TEC) network over the Asian sector. The electron density or TEC displayed wavelike structures rather than a regular diurnal pattern. Surprisingly, two humps, a common feature in the daytime equatorial ionization anomaly structure, disappeared. The SYISR observations revealed that multiple wind surges accompanied the downward phase propagation caused by atmospheric gravity waves (AGWs) originating from auroral zones. Meanwhile, strong upward and large downward drifts were respectively observed in the daytime and around sunset. The Thermosphere-Ionosphere Electrodynamics Global Circulation Model (TIEGCM) simulations demonstrated that abnormal ionospheric changes were attributed to meridional wind disturbances associated with AGWs and recurrent penetration electric fields corresponding to larger Bz southward excursions and disturbance dynamo. The complicated interplay between AGWs and disturbance electric fields contributed to this unique ionospheric variation.