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Geomagnetic Signatures of the Hunga Tonga Volcanic Eruption

Kusumita Arora 1, N.Phai Chandrasekhar 1

Abstract

The Hunga-Tonga volcano eruption released a tremendous amount of mass and energy into the atmosphere on January 15, 2022.  The related lightning strikes disrupt the worldwide electric circuit. In this study, we have mapped the (i) global geomagnetic disturbances caused by AGW generated by the volcanic eruption, (ii) Schumann Resonance parameters derived from modulations of ELF observations caused by the intense lightning phenomena that accompanied the volcanic eruption. Our analysis shows that (i) registration timing of geomagnetic disturbance at each observatory indicates the different modes of propagation between 180-350 m/s, indicating low-frequency Acousto Gravity Wave components causing ionospheric perturbations, (ii) noticeable changes in Schumann Resonance (SR) frequency modes (7 to 21 Hz) occurred in the total power linked to heightened lightning activity, (iii) velocities are found to be similar at similar distances in the northern and southern hemispheres from Hunga-Tonga, (iv) time difference between the SR and geomagnetic disturbance signature at observatories is found to be increasing with increase in distance from the eruption, (v) fluctuations in VTEC at the Indian and Russian sectors show that the geomagnetic disturbances are linked to. These observations linking a localised lithospheric phenomenon to ionospheric disturbances over 16000 km, spread over nearly 24 hours indicate a high degree of coupling between lithospheric and ionospheric processes. Additional geophysical data at different distances from Tonga, will provide crucial information on how atmospheric and ionospheric winds were impacted by the eruption, which in turn modified the geomagnetic field.