Three-Dimensional Reconstruction of Ionospheric Disturbances Using Tikhonov Regularization After 2022 Tonga Volcanic Eruption

Abstract

Following significant natural hazards, traveling ionospheric disturbances (TIDs) are generated that affect the ionosphere. Understanding the three-dimensional structure of these TIDs is crucial for understanding their propagation mechanisms. Ionospheric tomography is a viable method to reconstruct these three-dimensional structures. In this study, Tikhonov regularization is used to solve the ill-posed problem of ionospheric tomography following the Tonga volcanic eruption. The New Zealand Global Navigation Satellite Systems network was used to detect TIDs to infer changes in electron density within the ionospheric layers. To validate the reconstructed results, the electron density changes obtained from the tomography were used to reconstruct the detrended slant total electron content (dSTEC) and compared with observed dSTEC values. In addition, electron density profiles from radio occultation data were used for further evaluation. The results showed that the root mean square error of the tomography results could reach 0.228 TEC unit in the dSTEC reconstruction. The most pronounced TIDs were observed at altitudes between 200 and 300 km in agreement with radio occultation observations. Estimation of the speed of atmospheric waves showed that the disturbances propagated through the troposphere at about 360 m/s and reached speeds of up to 609 m/s in the ionosphere. As altitude increases, wave speed also rises, this demonstrates the ionosphere's potential for early warning. The Tikhonov method offers significant advantages in TIDs tomography due to its non-iterative nature, enabling rapid and precise three-dimensional reconstruction. This enhances the understanding of TIDs, improving monitoring and analysis of such events.