Wenbin Liang, Xiyan Sun, Yuanfa Ji, Xiaodong Ren
Abstract The total solar eclipse on 8 April 2024 provided a unique opportunity to investigate the three‐dimensional (3‐D) ionospheric response under enhanced solar activity over North America. In this study, we processed high‐density GNSS observations from ∼1,700 stations to derive vertical total electron content and applied a multi‐term sinusoidal detrending algorithm to extract differential TEC disturbances. A compressed sensing (CS)‐based tomography framework, incorporating a singular value decomposition‐derived dictionary, was employed to reconstruct 3‐D electron density (Ne) distributions with high spatial and temporal resolution. The results reveal pronounced altitude‐dependent electron density depletion, with maximum reductions in the F2 region (200–300 km) exceeding 2 × 10 11 el/m 3 . The depletion exhibited clear longitudinal and latitudinal propagation, with recovery times increasing eastward, highlighting strong horizontal‐vertical coupling. Post‐eclipse enhancements and a secondary depletion on 9 April were characterized with finer spatial detail than previous studies, and traveling ionospheric disturbances were quantified, revealing anisotropic zonal (1304 km, 0.81 km/s) and meridional (571 km, 0.42 km/s) propagation. Comparative analysis with the 2017 eclipse demonstrates that near‐solar‐maximum conditions led to deeper depletions and prolonged recovery. These findings advance understanding of multi‐scale eclipse‐induced ionospheric dynamics, provide robust 3‐D characterization of electron density evolution, and underscore the critical role of dense GNSS networks combined with CS tomography for resolving rapidly evolving ionospheric disturbances.