Xiongqi Guan, Wang Li, Xiangzhou Meng, Xiujiang Pan, Xiaoqing Zuo, Dongsheng Zhao, Kefei Zhang
Abstract The intense geomagnetic storm on 10–11 October 2024 (SYM‐H minimum ∼−346 nT) triggered significant global ionospheric disturbances, posing potential space weather risks to satellite navigation and communication systems. This study employs a combination of dense GNSS observation networks, in situ measurements from Swarm satellites, ionosonde data, and TIE‐GCM numerical simulations to analyze storm‐time ionospheric perturbations on a global scale, with a focused investigation over the North American sector. Using 3D GNSS tomography, we characterize the propagation and vertical evolution mechanisms of Large‐Scale Traveling Ionospheric Disturbances and the Storm Enhanced Density (SED) structure from a multidimensional perspective. Results reveal that intense polar Joule heating generated alternating bands of positive and negative ionospheric disturbances at high latitudes, propagating equatorward at a horizontal phase velocity of approximately 740 m/s. The disturbances peaked at ∼350 km altitude (dIED > ±0.3 × 10 11 el/m 3 ), corroborated by multiple ionosonde stations. A pronounced SED plume with significant vertical extent emerged around 18:00 UT on October 10. The steep gradient region at the plume edge coincided with strong irregularities identified by ROTI, and the plume persisted for 8 hr, gradually drifting westward before dissipating. This evolution was primarily driven by the equatorial super‐fountain effect induced by penetration electric fields, which propelled high‐density plasma to diffuse toward midlatitudes along the magnetic field lines. Concurrently, the downward plasma accumulation and physical compression driven by poleward neutral winds, combined with reduced recombination losses resulting from elevated O/N 2 ratios at mid‐to‐low latitudes, jointly sustained the plume structure.