17:15 〜 18:45
[SEM12-P12] Magnetic field variations observed at Atele station in Tonga due to 2022 Hunga Tonga-Hunga Ha'apai volcanic eruption
キーワード：2022年フンガ・トンガ=フンガ・ハアパイ火山噴火、地磁気変化
Geomagnetic field observations are being conducted in 'Atele, Tonga, with a purpose to study short-term (decadal scale) geomagnetic secular variations in collaboration with the Earthquake Research Institute of the University of Tokyo and the Tongan Geological Services. The characteristics of the magnetic field variations at 'Atele station due to phenomena related with the Hunga Tonga-Hunga Ha'apai (HTHH) volcanic eruption on January 15, 2022, are shown and discussed in this presentation.
Iyemori et al. (2022) and Yamazaki et al. (2022) reported that magnetic field variation originated from the volcanic eruption with a period about 4 minutes were observed at Apia, Samoa, that is about 835 km NNE from HTHH. The cause of this variability has been identified as electric currents induced in the ionosphere by atmospheric acoustic resonance caused by the eruption. At the 'Atele station, about 74 km south of HTHH, magnetic field variations with a similar period but with an amplitude ten times larger than that at Apia were observed. The trajectory of the magnetic field variations in the horizontal plane is aligned in the NE-SW direction at 'Atele but it is almost in the East-West direction at Apia. The characteristics of local electric current in the ionosphere that caused magnetic field variation at 'Atele and Apia is discussed using these observations.
In addition to the variations due to the atmospheric acoustic resonance, a magnetic field variation that started at the time of volcanic eruption and lasted for about two hours is observed at the two stations. The cause of the variation is not certain at present but the difference in polarity of the change at 'Atele and Apia implies that the variation is generated by local electric current. The possibility of generating such electric current that cause the variation by phenomena related with the volcanic eruption is discussed.
Iyemori et al. (2022) and Yamazaki et al. (2022) reported that magnetic field variation originated from the volcanic eruption with a period about 4 minutes were observed at Apia, Samoa, that is about 835 km NNE from HTHH. The cause of this variability has been identified as electric currents induced in the ionosphere by atmospheric acoustic resonance caused by the eruption. At the 'Atele station, about 74 km south of HTHH, magnetic field variations with a similar period but with an amplitude ten times larger than that at Apia were observed. The trajectory of the magnetic field variations in the horizontal plane is aligned in the NE-SW direction at 'Atele but it is almost in the East-West direction at Apia. The characteristics of local electric current in the ionosphere that caused magnetic field variation at 'Atele and Apia is discussed using these observations.
In addition to the variations due to the atmospheric acoustic resonance, a magnetic field variation that started at the time of volcanic eruption and lasted for about two hours is observed at the two stations. The cause of the variation is not certain at present but the difference in polarity of the change at 'Atele and Apia implies that the variation is generated by local electric current. The possibility of generating such electric current that cause the variation by phenomena related with the volcanic eruption is discussed.