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Abstract The global 3‐dimensional structure of the concentric traveling ionospheric disturbances (CTIDs) triggered by 2022 Tonga volcano was reconstructed by using the 3‐dimensional computerized ionospheric tomography (3DCIT) technique and extensive global navigation satellite system (GNSS) observations. This study provides the first estimation of the CTIDs vertical wavelengths, ∼736 km, which was much larger than the gravity wave (GW) vertical wavelength, 240–400 km, estimated using ICON neutral wind observations. Notable trend with the variation of azimuth was also found in horizontal speeds at 200 and 500 km altitudes and differences between them. These results imply that (a) the global propagation of Lamb waves determined the arrival time of local ionospheric disturbances, and (b) the arriving Lamb waves caused vertical atmospheric perturbations that are not typical of GWs, resulting in local thermospheric horizontal wave propagation which is faster than the Lamb wave propagation at lower altitudes. 

Abstract GPS total electron content (TEC) measurements were used to investigate high‐m ultralow frequency (ULF) waves during the recovery phase of a geomagnetic storm. ULF wave signals in TEC data show high coherence and significant common power in the wavelet coherence and cross wavelet transform analyses with magnetic field radial component data from GOES‐15. They did not cause significant ionospheric scintillation or ground magnetic signatures due to ionospheric screening effects. An automatic identification procedure is developed to identify ULF wave signature in TEC data from 10 GPS receivers on January 25, 2016. The waves were mainly distributed on the dayside and post dusk sector from ∼64° to ∼71° magnetic latitude. This is the first time that the large‐scale 2D spatial structure and temporal evolution of high‐m ULF waves are revealed, which demonstrates TEC measurements as an effective high‐m ULF wave remote sensing tool.