Auroral Effect on Mid‐Latitude Ionospheric Disturbances Over Europe During the Extreme Geomagnetic Storm of 10 May 2024
Grzegorz Nykiel, Joanna Kanska, Hiroatsu Sato, Shin‐ichiro Oyama, Kazuo Shiokawa, David R. ThemensAbstract
Large ionospheric disturbances were observed over Europe during the extreme geomagnetic storm on 10 May 2024. This study analyzes GNSS‐derived total electron content (TEC) and all‐sky imager data to investigate these disturbances. Pronounced TEC enhancements, irregularities, and strong gradients were confined to the auroral region above the mid‐latitudes. These anomalies evolved coherently with the equatorward expansion of the optical aurora. Large‐scale TEC disturbances were found to be moving at mid‐latitudes with an equatorward velocity of 726 m/s and an amplitude of up to 7 TECU. These characteristics were indicative of the auroral expansion rather than of large‐scale traveling ionospheric disturbances (LSTIDs), which exhibited weaker amplitudes near the auroral boundary. This finding contrasts with the interpretation of some previous studies on GNSS observations. This study demonstrates the visualization of the auroral oval at mid‐latitudes using TEC and TEC‐derived parameters.