Magnetic Signatures of the 15 January 2022 Hunga Tonga–Hunga Ha'apai Volcanic Eruption

On 15 January 2022, at around 04:00 UTC, the submarine volcano Hunga Tonga‐Hunga Ha'apai explosively erupted. We examine data from 10 Pacific Ocean geomagnetic observatories and process the data using both high pass filters and cross‐wavelet analyses to enable evaluating 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. At CBI and IPM, the magnetic signal may be due to both the eruption's tsunami water wave and atmospheric/ionospheric sources. Our results suggest that the magnetic signatures from the eruption are identifiable and may be further separated in future studies. Plain Language Summary On 15 January 2022, at around 04:00 UTC, the submarine volcano Hunga Tonga‐Hunga Ha'apai erupted in a violent explosion. Previous studies have identified magnetic signals from earthquake‐created tsunamis, however, no such studies have identified marine magnetic signals from eruption‐created tsunamis. Identifying magnetic signals from different aspects of a submarine eruption can lead to a better understanding of the eruption's mechanisms, as well as potentially improve warning systems for the tsunami created by the eruption. Toward this aim, we examine data from 10 Pacific Ocean geomagnetic observatories. We processed the data using mathematical methods that enable examining the different wave components of the timeseries. We find magnetic signals likely caused by the eruption at three different Pacific island observatories (API‐ Western Samoa, CBI‐ Chichijima Island, and IPM‐ Easter Island). Key Points Magnetic signals of 3–8 min period, and visible in both horizontal and vertical field components, arrived at Western Samoa (API) Both Chichijima Island (CBI) and Easter Island (IPM) had local magnetic signatures concurrent with the eruption's water wave arrival The magnetic signals at CBI and IPM may be due to both the eruption's tsunami water wave and atmospheric/ionospheric waves