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Abstract:
The submarine volcano Hunga Tonga-Hunga Ha'apai erupted explosively at around 04:15 on 15 January 2022 UTC. Our previous study, Schnepf et al. (2022), examined data from 10 Pacific Ocean geomagnetic observatories and processed the data using both high pass filters and cross-wavelet analyses to evaluate the time-frequency characteristics of the magnetic signals across the Pacific region. At the Western Samoa observatory (API), magnetic signals of 3-8 min period, and visible in both vertical and horizontal fields, arrived at ∼04:44 UTC. The observatories at Chichijima Island (CBI) and Easter Island (IPM) both had local magnetic signatures concurrent with the eruption's water wave arrival and period ranges from, respectively, 13–93 and 5–100+ min. Yamazaki et al. (2022) revealed that the 3.8mHz (4.4 min period) magnetic oscillation at API was due to the E region dynamo excited by acoustic resonance above the eruption region. Recently, we further recognized that the magnetic variation at CBI was induced by motional induction in the ocean associated with both the pressure-driven tsunami, which was caused by atmospheric pressure wave such as Lamb wave, and the normal tsunami originating from the sea surface deformation at the eruption location. We performed numerical simulations of the pressure-driven and normal tsunamis, and then simulated magnetic variation at CBI with the time-domain electromagnetic simulation code of Minami et al. (2017). In the presentation, we present an overview of the magnetic signatures due to the eruption event referring to the recent publications, and report the details of the magnetic signature observed at CBI.
