[M-IS19] 大気電気学：大気電気分野の物理現象解明から防災への応用まで

[MIS19-12] Lower Ionospheric Disturbance Analysis Caused by Atmospheric Gravity Waves during 2022 Hunga Tonga – Hunga Ha’apai Eruption Using Dense VLF/LF Observation Network over Japan

*Antrisha Daneraici Setiawan¹、Yasuhide Hobara^1,2,3、Alexander Shvets^3,4 (1.University of Electro-Communication, Chofu, Tokyo, Japan、2.Center for Space and Radio Engineering, University of Electro-Communications Chfu, Tokyo, Japan、3.Research Center for Realizing Sustainable Societies, The University of Electro-Communication, Chofu, Tokyo, Japan、4.O. Ya. Usikov Institute for Radiophysics and Electronics of the National Academy of Sciences of Ukraine, Kharkive, Ukraine)

キーワード：Ionosphere, VLF/LF, Hunga Tonga - Hunga Ha'apai Eruption, Atmospheric Gravity Waves, Tsunami

The Hunga Tonga – Hunga Ha’apai submarine volcano erupted on 2022 January 15^th. The eruption is big enough to cause a visible wave to propagate worldwide. The propagating wave causes the lower ionospheric perturbations. The IR sensor camera from the Himawari8 satellite and the temperature deviation mapping method are used to observe the visible atmospheric gravity waves (AGWs) from the eruption. At least three waves, visible in the temperature deviations, are coming across the VLF/LF transmitter signal observation network deployed by the University of Electro-Communications around Japan. The waves were found to have arrived at 11:20, 12:30, and 14:30 UT from the Hunga Tonga – Hunga Ha’apai after its eruption at 04:10 UT. It is possible to analyze the correlation between the wave arrival time and the fluctuation in the observed VLF/LF electric signal amplitude as indicative of the lower ionospheric perturbation. The VLF/LF transmitters are located in Hawaii (NPM), Australia (NWC), and Japan (JJY and JJI). All of the VLF/LF receivers are located in Japan, i.e., Chofu (CHO), Tsuyama (TYM), Nakashibetsu (NSB), and Yamaguchi (YMG). With a total of 16 possible paths between transmitters and receivers. The wavelet spectrograms of the VLF/LFsignal amplitude show perturbations with a 1 – 6 minute period right after the arrival of the first wave or Lamb wave. However, this is not observed for NWC networks due to their crossing the solar terminator. The second wave, Pekeris wave, causes a perturbation observed by all the receiving stations, except NPM paths with a 20-minute period, while the third wave, associated with tsunami-induced atmospheric gravity waves, caused the strongest perturbation with a 20-minute period in JJI and JJY paths.