日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 P (宇宙惑星科学) » P-EM 太陽地球系科学・宇宙電磁気学・宇宙環境

[P-EM09] Vertical coupling in the atmosphere and Ionosphere

2019年5月29日(水) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:Liu Huixin(九州大学理学研究院地球惑星科学専攻 九州大学宙空環境研究センター)、Chang Loren(Institute of Space Science, National Central University)、大塚 雄一(名古屋大学宇宙地球環境研究所)

[PEM09-P05] Observation and simulation of propagation of coseismic infrasound to the ionosphere

*Jaroslav Chum1 (1.Institute of Atmospheric Physics of the Czech Academy of Sciences)

キーワード:coseismic perturbation in the ionosphere, infrasound, nonlinear propagation

Vertical motion of the ground surface caused by seismic waves generates acoustic waves that propagate nearly vertically upward owing to supersonic speed of seismic waves. As the air density decreases with height, the amplitude of acoustic waves increases to conserve the energy flux up to the altitudes where the air is so rarefied that it cannot sustain the propagation and the waves start dissipating. For distances up to about 1500 km from the epicenter of the strong earthquakes (M>7), the amplitude (oscillation velocity) of infrasound waves reaches significant values in the upper atmosphere. Consequently, the nonlinear phenomena start to play an important role. Spectral content of the wave packet is changed and the energy is transferred to lower frequencies, which can cause the formation of roughly bipolar N-shaped pulse. The simulation results are compared with observation for selected examples. It is also shown that only infrasound with periods larger than about 10 s (generated by long period seismic waves) can reach the ionospheric heights, namely the F layer where it can be easily detected.