Japan Geoscience Union Meeting 2022

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[U-09] Submarine volcanic eruption in Tonga accompanied by a meteo-tsunami

Mon. May 30, 2022 11:00 AM - 1:00 PM Online Poster Zoom Room (40) (Ch.40)

convener:Toshiyuki Hibiya(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), convener:Fukashi Maeno(Earthquake Research Institute, University of Tokyo), convener:Kensuke Nakajima(Department of Earth and Planetary Sciences,Flculty of Sciences,Kyushu University), convener:Yoshihiko Tamura(Research Institute for Marine Geodynamics, Japan Agency for Maine-Earth Science and Technology), Chairperson:Toshiyuki Hibiya(Department of Ocean Sciences, Tokyo University of Marine Science and Technology), Fukashi Maeno(Earthquake Research Institute, University of Tokyo), Kensuke Nakajima(Department of Earth and Planetary Sciences,Flculty of Sciences,Kyushu University), Yoshihiko Tamura(Research Institute for Marine Geodynamics, Japan Agency for Maine-Earth Science and Technology)

11:00 AM - 1:00 PM

[U09-P35] Generation of trans-equatorial field-aligned current by the 2022 Hunga Tonga Hunga Ha'apai volcanic eruption

*Toshihiko Iyemori1, Michi Nishioka2, Yuichi Otsuka3, Atsuki Shinbori3 (1.Kyoto University, 2.NICT, 3.Nagoya University)

Keywords:Acoustic resonance, Field-aligned currents, Geomagnetic field oscillation, GPS-TEC oscillation

Just after the 2022 Hunga Tonga Hunga Ha'apai volcanic eruption, geomagnetic oscillations with periods near the vertical acoustic resonance around 4 minutes are observed at Apia and Honolulu geomagnetic observatories with amplitude about 2 nT and 0.2 nT, respectively. The volcanic eruption started around 04:14 UT on January 15, 2022 and the oscillations appeared at 04:21UT at Apia, Samoa, only about 7 minutes after the start of eruption. Because the distance between the volcano and Apia is about 841km, it takes about 40 minutes for a sound wave to propagate from the volcano to Apia. Therefore, it is more plausible to assume that the magnetic oscillation observed at Apia about 7 minutes after the eruption is caused by the sound waves propagated vertically upward to the ionosphere and generated an electric current. The oscillations in the east-west component of geomagnetic fields are anti-phase with zero time lag between the two geomagnetic stations. The Honolulu locates near the geomagnetic conjugate point of the Apia. The coherent appearance of geomagnetic oscillation at Honolulu strongly support the idea that the ionospheric current generated over the volcano diverted as a field-aligned current which flew to the opposite hemisphere and caused the geomagnetic oscillation at Honolulu. The GPS TEC oscillations with period similar to geomagnetic field oscillations are observed at the GPS stations both in Samoa and Hawaii. The generation mechanism of the TEC oscillations over Hawaii area is also discussed.