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Please use this identifier to cite or link to this item: https://dspace.lboro.ac.uk/2134/382

Title: Nonlinear internal waves in the upper atmosphere
Authors: Caillol, P.
Keywords: internal waves
viscous and stratified shear flow instability
Prandtl number
Issue Date: 2005
Abstract: This paper considers the large-scale dynamics generated in the upper atmosphere by the destabilization of a linear internal gravity wave and its eventual restabilization through nonlinear processes into a coherent pattern. The assumption of a strongly dissipative medium is relevant to wave propagation in the thermosphere range above 100 km. A parametric instability analysis is carried out involving the Froude, Reynolds and Prandtl numbers, and the following parameters: friction, wave incidence and disturbance periodicity. A solution of the motion is sought with the help of a multiscale technique based upon the hypothesis of large-scale flow. The leading-order amplitude equation governing this dynamics contains the Cahn-Hilliard equation, but possesses, as well, a dispersive term depending on the Prandtl number, a large-scale damping proportional to the overall Richardson number and a quadratic term modelling the incidence effects. A numerical and analytical study of this equation is given. An internal-wave stability criterion is obtained which shows the possibility of obtaining coherent structures for large Froude numbers.
Description: This is a pre-print.
URI: https://dspace.lboro.ac.uk/2134/382
Appears in Collections:Pre-prints (Maths)

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