Lightning and Gravity Wave Signatures Produced by the Hunga-Tonga Volcanic Eruption on Global Geomagnetic Data

Acoustic gravity waves (AGWs) have a significant impact on the thermosphere-ionosphere (T-I) system by increasing ionisation variability, transporting energy, velocity, momentum, and creating additional horizontal gradients in the T-I, all of which influence electromagnetic wave propagation and cause changes in the geomagnetic field. Ground magnetic disturbance measurements can thus map the global and local spatial distribution of T-I current systems. The Hunga-Tonga volcano eruption released a tremendous amount of mass and energy into the atmosphere on 15 January 2022, causing AGWs. Furthermore, the related lightning strikes disrupt the Global electric circuit. In this study, we look at (a) global geomagnetic disturbances caused by AGW constrained by VTEC amplitudes at two different sectors, (b) Schuman resonances (SR) parameters derived from modulations of ELF observations caused by the intense lightning phenomena that accompanied the volcanic eruption. Our analysis shows that (a) registration timing of geomagnetic disturbance at each observatory indicates the different modes of propagation between 180 and 350 m/s, indicating low-frequency AGW components, (b) noticeable changes in SR frequency modes (7-21 Hz) occurred in the total power between 04:15 and 05:45 UT hr at Patiyasar, India, linked to heightened lightning activity, (c) velocities are found to be similar at similar distances in the northern and southern hemispheres from Hunga-Tonga, (d) time difference between the SR and geomagnetic disturbance signature at observatories is found to have no relation with distance from the eruption, (e) fluctuations in VTEC at the Indian and Russian sectors show that the geomagnetic disturbances are linked to ionospheric perturbations.