[P-EM22] [JJ] Physics and Chemistry in the Atmosphere and Ionosphere

[PEM22-03] Ionospheric disturbances associated with volcanic eruptions observed by GPS-TEC and HF Doppler sounding

*Aritsugu Chonan¹, Hiroyuki Nakata¹, Hiroyo Ohya¹, Toshiaki Takano¹, Ichiro Tomizawa², Takuya Tsugawa³, Michi Nishioka³ (1.Graduate School of Engineering, Chiba University, 2.The University of Electro–Communications, 3.National Institute of Information and Communications Technology)

Keywords:Ionosphere, GPS-TEC, HF Doppler

It is reported that ionospheric disturbances are caused not only by solar-terrestrial conditions but the phenomena below the ionosphere such as earthquakes, typhoons and volcanic eruptions. Compared with ionospheric disturbances caused by earthquakes, there are very few studies examining the ionospheric disturbances associated with volcanic eruptions.
In this study, we have examined ionospheric disturbances associated with volcanic eruptions using GPS-TEC and HF Doppler sounding. We detected ionospheric disturbances associated with Mt. Asama eruption at 11:02 UT on Sep., 1st, 2004. In HF Doppler sounding observation, the spiky disturbances whose frequency is about 7 - 16 mHz was observed firstly. Following this disturbances, longer-period disturbance was appeared, whose frequency is about 3 - 5 mHz. The former disturbance was also observed by GPS-TEC,
whose ionospheric pierce points were located near the Mt. Asama. From the propagation time of this disturbance, it is possible that the eruption generated shock waves which propagated to the higher ionosphere. In terms of the frequency, the latter disturbances observed by HFD sounding shows the resonance of the atmospheric wave between the lower ionosphere and the ground.