Multi‐Timescale Responses of the EEJ to Energy Deposition in the Auroral Region During the 10 May 2024 Superstorm

Abstract Based on data from ground‐based magnetometers in four longitudinal sectors across the Americas and Asia, this study presents a detailed analysis of the equatorial electrojet (EEJ) driving mechanisms during the intense geomagnetic storm of May 10–11, 2024. Our results reveal a clear evolution of the driving mechanisms throughout the storm. During the main phase, EEJ variations were predominantly driven by the prompt penetration electric field (PPEF), although an early onset of the disturbance dynamo electric field (DDEF) was also identified. In the recovery phase, however, the dynamic process transitioned into a complex, multi‐timescale competition. A slowly varying, DDEF‐dominated background field contended with frequent, PPEF‐like electric field penetrations driven using internal magnetospheric processes. This complexity is highlighted by several significant EEJ disturbances that cannot be explained by typical Interplanetary Magnetic Field (IMF) conditions, such as a pulse‐like disturbance during the main phase and fluctuations without an IMF trigger in the late recovery phase. The drivers of these disturbances are revealed to be multifaceted. While some disturbances can now be attributed to the PPEFs following magnetospheric compression by solar wind dynamic pressure pulses, others are suggested to be driven by either high‐latitude electric fields penetrating from magnetospheric sources (e.g., subauroral polarization streams) or by DDEFs with an atmospheric origin. Furthermore, this study highlights the critical role of the nightside EEJ in monitoring global electric field fluctuations, demonstrating that it provides a more complete view of the global morphology of storm‐time electric fields and their competing drivers. These findings demonstrate that equatorial electrodynamics during a major geomagnetic storm result from a non‐linear interaction between conventional driving mechanisms and transient, internally driven magnetospheric processes.