Ionospheric Electron Density Perturbation Caused by Tsunami-Induced Gravity Waves
Date Issued
2009
Date
2009
Author(s)
Mai, Chao-Lun
Abstract
A tsunami propagating on an open sea can induce an internal gravity wave (IGW) into thetmosphere. The IGW will be amplified due to the decrease of mass density with height,nd will cause a transient vibration in the ionosphere starting at about 150 km above theea level. Global positioning system (GPS) and ground-based HF Doppler radar have beeneported to detect such ionospheric variation.n this work, we propose a complete model which incorporates the loss mechanisms dueo thermal conduction, viscosity, and ion drag. A dispersion relation is derived which revealshat only a specific range of spatial spectrum can propagate through the atmosphere tohe ionosphere, and IGW amplitude will reach a maximum at certain altitude. Throughon-neutral collision, chemical loss, and photoionization, electron irregularity is induced inhe passage of the gravity wave. The waveform, amplification factor, propagation speed andravel time can be applied up to more than 800 km high.he ionospheric electron density irregularity induced by the Sumatra tunami on December6, 2004 was detected by satellite-born altimeter and global positioning system (GPS)round the Indian Ocean. The model is applied to the 2004 Sumatra tsunami profile which isestored from the satellite recorded data. The tsunami wave triggers an intenal gravity waven the atmosphere, which propagates upward with an average velocity of about 700 - 800/s into the ionosphere and significantly disturbs the electron density by 3 to 4 TECU. TheGW is then trapped at about 400 km height, and moves horizontally with the same speed ashat of the tsunami. Approximately 11 minutes after the tsunami triggers the atmosphericisturbances, ionospheric irregularity starts to be detected by the satellites that pass over,nd peak perturbation of TEC will be observed in about an hour. The simulation resultsell explain the TEC observation in magnitude, waveform, and time delay.
Subjects
tsunami
gravity wave
ionosphere
GPS
Type
thesis
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