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Nonlinear acoustic waves in the viscous thermosphere and ionosphere above earthquake
Author(s) -
Chum J.,
Cabrera M. A.,
Mošna Z.,
Fagre M.,
Baše J.,
Fišer J.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023450
Subject(s) - thermosphere , waveform , infrasound , gravity wave , amplitude , acoustic wave , shock wave , physics , doppler effect , dissipation , geophysics , atmosphere (unit) , ionosphere , geology , atmospheric wave , sonic boom , nonlinear system , rayleigh wave , gravitational wave , wave propagation , meteorology , acoustics , mechanics , supersonic speed , optics , quantum mechanics , voltage , astronomy , thermodynamics , astrophysics
The nonlinear behavior of acoustic waves and their dissipation in the upper atmosphere is studied on the example of infrasound waves generated by vertical motion of the ground surface during the M w 8.3 earthquake that occurred about 46 km from Illapel, Chile on 16 September 2015. To conserve energy, the amplitude of infrasound waves initially increased as the waves propagated upward to the rarefied air. When the velocities of air particles became comparable with the local sound speed, the nonlinear effects started to play an important role. Consequently, the shape of waveform changed significantly with increasing height, and the original wave packet transformed to the “N‐shaped” pulse resembling a shock wave. A unique observation by the continuous Doppler sounder at the altitude of about 195 km is in good agreement with full wave numerical simulation that uses as boundary condition the measured vertical motion of the ground surface.