A Contrasting TEC Behavior Over the Low‐Latitude Post‐Midnight Sector During Recovery Phases of May and October 2024 Storms: Possible Role of PPEF, DDEF, and O/N ₂

Abstract

The present study reports on the variability of the post‐midnight ionosphere over the low‐latitude sector during the recovery phases of the May and October 2024 storms. Multi‐instrument observations, comprising global navigation satellite system total electron content (TEC), F‐layer peak height, electron density profiles, and column O/N ₂ measurements, were employed to examine this variability. Interestingly, the TEC over the low‐latitude American sector showed contrasting behavior on the two nights (11 May 2024 and 11 October 2024). On 11 October 2024, TEC exhibited a significant enhancement exceeding 20 TECu from the post‐midnight to morning period, whereas on 11 May 2024, TEC decreased by approximately 5 TECu. The eastward disturbance dynamo electric field (DDEF), driven by storm‐time modifications of the thermospheric neutral wind, likely contributed to the significant uplift of the F‐layer on 11 October. This uplift also allowed the TEC to remain elevated for a longer period due to reduced quenching at higher altitudes. Additionally, the enhanced O/N ₂ also contributed to the elevated TEC on 11 October. However, the reduction of TEC on 11 May was likely caused by the westward prompt penetration electric field (PPEF). The westward PPEF during the post‐midnight period contributed to the descent of the F‐layer with the consequent downward transport of plasma, thus enhancing chemical loss and reducing TEC. The present study evaluates the potential contributions of plasma transport to the contrasting TEC variations and highlights the distinct roles played by storm time generated electric fields in shaping the dynamics of the low‐latitude ionosphere.