Open AccessAsymptotic behaviour of decay rates of internal waves in a rotating stratified spherical shell
Author(s) -
Friedlander Susan
Publication year - 1989
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1989.tb04448.x
Subject(s) - physics , stratification (seeds) , inviscid flow , dissipative system , internal wave , mechanics , oscillation (cell signaling) , rotation (mathematics) , stratified flows , classical mechanics , computational physics , stratified flow , geometry , quantum mechanics , mathematics , seed dormancy , turbulence , botany , germination , genetics , dormancy , biology
Summary. Boundary layer techniques are used to examine the dissipative decay of an internal oscillation that is a member of the inviscid spectrum of normal modes for a rotating fluid shell stratified under a radially directed gravitational field. A formula is derived for the decay factor on the so‐called homogeneous spin‐down time‐scale. Estimates are obtained for the size of the decay factor as a function of wavelength, a function of the frequency and a function of a parameter A which measures the ratio of the stratification strength to the rotation strength. It is shown that all modes decay on the spin‐down time‐scale. The results are interpreted in the context of a model for the Earth's fluid core. It is observed that the presence of regions of unstable stratification may increase the decay rate for oscillations at frequencies less than twice the rotation frequency.