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-P30] Periodic variation of the Doppler shift frequency in association with the Tonga eruption

*Hiroyuki Nakata1, Keisuke Hosokawa2, Yuichi Otsuka3, Ichiro Tomizawa2 (1.Graduate School of Engineering, Chiba University, 2.Department of Communication Engineering and Informatics, The University of Electro-Communications, 3.Institute for Space-Earth Environmental Research, Nagoya University)

Keywords:Ionosphere, HF radio wave, Doppler shift frequency, Tonga eruption

The eruption of the Tonga submarine volcano occurred at 4:00 UT on January 15, 2022, and was accompanied by a large-scale atmospheric wave. TEC disturbances were observed in New Zealand about one hour after the eruption and about two hours and a half later in Australia. In Japan, a pressure variation of about 2 hPa was observed about 7 hours after the eruption (11:00-12:00 UT), and TEC disturbances were also observed in association with this pressure variation. In addition, earlier than the arrival of this pressure variation, TEC disturbances were also observed around Japan. Because Japan and Australia are located in a magnetic conjugate position, it is thought that the TEC disturbances generated in Australia propagate in Japan through the magnetic field lines. Such conjugate relation of disturbances through magnetic field lines has also been reported for coseismic ionospheric disturbances (Iyemori et al., 2005).

The Doppler shift variation with a period of about 4 minutes was observed in association with the variation before the arrival of the pressure variation. The variation of Doppler shift frequency was observed in the radio wave at 5006 kHz (transmitter: Chofu, receiver: Sarobetsu), but no variation was observed at 3925 kHz (transmitter: Nemuro, receiver: Chiba). From the fact that the radio wave at 3925 kHz is reflected at a lower altitude, it is suggested that the variation occurred in the F region but not in the E region. In this presentation, we will present the results of detailed analysis together with TEC variations.