著者

中島 悠貴

出版者

北海道大学

巻号頁・発行日

2018-03-22

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I discuss the propagation of very low frequency infrasound that come from volcanic eruptions from near surface to the ionosphere based on the observations of GNSS-TEC, broadband seismometers and barometers. Infrasound or some other atmospheric wave under ~10 mHz can reach to the ionosphere and shake the ionized atmosphere. For example, a great earthquake induces not only ground motions or tsunamis but also atmospheric perturbations and some of them propagate upward to the ionosphere. Such waves are interpreted as the acoustic modal wave, the tsunamigenic gravity wave or the atmospheric wave coupled to the seismic Rayleigh wave. Ionospheric perturbations by volcanic eruptions are also sometimes reported. In my master thesis written in 2015, I discussed the ionospheric disturbances made by the 2014 Kelud volcano eruption. It induced acoustic trap mode by continuous eruption. In the thesis, I would introduce the investigation about the propagation of the atmospheric disturbance by the 2015 Kuchinoerabujima eruption. I analyzed 1 Hz sampled GNSS-TEC time series, broadband seismograms and barograms installed around the volcano. The features of the ionospheric disturbances observed in the two case are totally different. I can confirm again with more assurance that the difference comes from the sequence of the volcanic eruptions.