Strong Altitudinal Discrepancies in the Polar Tongue of Ionization During the Super Geomagnetic Storm on 10 May 2024

The Tongue of Ionization (TOI) is the typical ionospheric irregularity in the polar region. During the superstorm on 10 May 2024, an unexpected altitudinal discrepancy of TOI in the Southern Hemisphere is observed. Three-dimensional Computerized Ionospheric Tomography (3DCIT) results show that between 21:30 and 22:30 UT, the TOI decays at 500 km while simultaneously expands at 800 km, exhibiting a contrasting vertical evolution that has not been previously reported. Simulations reveal that the dayside upward E×B drift produce the higher density in SED region in the top ionosphere. Then, at 800 km, more plasma is moved into the polar region, forming the stronger TOI. Beyond the commonly emphasized dayside E×B drift transport, nightside meridional winds also play a crucial role in generating the altitudinal discrepancies. Strong equatorward winds uplift plasma along the geomagnetic field lines and supplied sufficient plasma to maintain the TOI structure during nighttime in the top ionosphere.