Penetration Electric Fields and Disturbance Dynamo Effects During the November 2025 Geomagnetic Storm

Abstract \noindent The November 2025 geomagnetic storm generated pronounced perturbations in the equatorial and low-latitude ionosphere through enhanced magnetosphere--ionosphere--thermosphere coupling. This study quantifies the relative contributions of prompt penetration electric fields (PPEFs) and disturbance dynamo electric fields (DDEFs) in regulating storm-time electrodynamics across multiple longitudinal sectors, including Africa, South America, and Southeast Asia. GNSS-derived total electron content (TEC) data from six IGS stations, ground-based magnetometer measurements from two stations, and solar wind, thermospheric O/N$_2$ ratio, and geomagnetic indices (Dst, Kp, $V_{\mathrm{sw}}$, $E_y$, IMF) were employed to characterize the ionospheric response. Results show that PPEFs dominate the storm main phase, producing rapid eastward plasma drifts, intensified equatorial electrojet (EEJ), and TEC enhancements up to $\sim 80\%$ above quiet-time levels. Conversely, DDEFs emerge during the recovery phase, generating westward electric fields that suppress TEC and weaken or reverse EEJ signatures. Spatial analysis reveals significant longitudinal and latitudinal asymmetries, reflecting regional geomagnetic configurations, background ionospheric conditions, and storm-driven thermospheric wind dynamics. These findings highlight the sequential and competing roles of PPEFs and DDEFs in shaping storm-time equatorial and low-latitude ionospheric variability, emphasizing the necessity of incorporating both mechanisms into ionospheric forecasting frameworks to improve GNSS performance and mitigate space weather impacts.