The variometric approach for the monitoring of natural hazard-induced ionospheric perturbations

This work shows how the VARION (Variometric Approach for Real-Time Ionosphere Observation) algorithm, able to estimate the TEC variations in real-time, can be used to shed the light on the mechanism of Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) and thus to be used for ionospheric monitoring of natural hazards events. In particular, we present the methodology of Total Variometric Approach (TVA) was developed to estimate the tsunami genesis and to support classic methods for tsunami warning system. TVA is based on the joint application of VADASE (Variometric Approach for Displacements Analysis Standalone Engine) and VARION to estimate ground shaking, co-seismic displacements and TEC disturbances, using the same real-time GNSS data stream. Furthermore, we present an oceanic-ionospheric joint analysis after the 2022 Tonga eruption. We report on the reversed amplitude of the two phenomena in the oceans and in the ionosphere. The sea-surface perturbation caused by the Lamb wave was not significant, while ionospheric perturbation was considerable. In contrast, the regular tsunami waves manuscript reached ~1m around New Caledonia-New Zealand and ~2m along the Chilean coastline; however, the associated ionospheric perturbation was quite small, half the size of the Lamb wave perturbation. We finally explore the possibility to increase the amount of available data for a denser ionospheric monitoring, applying VARION also to observations coming from geostationary satellites, from ship-based GNSS receivers and from smartphones.