Daytime Ionospheric Density Enhancement Driven by Poleward Neutral Wind Shear Associated With Gravity Waves During the November 2025 Geomagnetic Storm

Abstract The threefold daytime electron density increases, along with strong poleward meridional winds exceeding 200 m/s were captured by Sanya Incoherent Scatter Radar (SYISR) during the geomagnetic storm of 12 November 2025. The great ionospheric enhancements were extending to mid‐latitudes over 40° observed by total electron content (TEC) from Beidou geostationary satellites. Thermosphere‐Ionosphere Electrodynamics Global Circulation Model (TIEGCM) reproduced the observed features during this storm. In particular, the traveling atmospheric disturbances (TADs) with a poleward phase speed of ∼710 m/s were present during the simulated TEC enhancements. Analysis of the O + continuity equation revealed that the great ionospheric increases were dominated by sharp shear in the poleward meridional winds associated with TADs. Moreover, meridional wind vertical shear was the primary controlling factor, with horizontal shear acting as a secondary contributor. These findings demonstrated that strong meridional wind shear drives the accumulation of ionospheric electron density, regardless of the wind direction.