Specification and Parameter Estimation of Traveling Ionospheric Disturbances Originating From Tsunami and Ionospheric Events Using GNSS Data

The ionosphere exhibits irregularities known as Traveling Ionospheric Disturbances (TIDs). This study aims to provide a method for estimating TID parameters and investigate the differences between tsunami TIDs and ionospheric TIDs using Global Navigation Satellite Systems (GNSS) data. The method is based on the reconstruction of half sinusoidal wave structures in the differential Total Electron Content (dTEC) time series and the extraction of parameters best fitted to the actual data. The reconstructed results were consistent with the dTEC time series, providing automatic TID parameters. The proposed method uses the frequency and wavelength to estimate the final speed, which is validated by keograms and confirms the TID parameter estimation by the method. Comparing the TIDs of tsunamis from 2011 to 2024 and ionospheric TIDs from 2011 to 2023, both types of TIDs exhibited horizontal scale characteristics similar to those of medium‐scale traveling ionospheric disturbances (MSTIDs). However, tsunami TIDs display distinct features with varying propagation speeds and frequencies, deviating from the typical MSTID behavior during the early stage of TID generation caused by the earthquake shock that produced the tsunami. The results indicated that the propagation speed of tsunami TIDs ranged from approximately 250 to nearly 3,000 m/s, with frequencies between 1.3 and 3.3 mHz. For ionospheric TIDs, the speed ranged from 130 to 250 m/s and the frequency ranged from 1.3 to 1.8 mHz. These results demonstrate that the proposed method can estimate the TID parameters and potentially distinguish the characteristics of tsunami TIDs from typical ionospheric TIDs.