Inertial modes of the earth's fluid core
Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy
The Earth’s outer core is a rotating ellipsoidal shell of compressible, stratified and self-gravitating fluid. As such, in the treatment of geophysical problems a realistic model of this body needs to be considered. In this work we consider a compressible and stratified fluid core model with different stratification parameters, related to the local Brunt- Väisälä frequency. We use the three potential description (3PD) to study the effects of the core’s density stratification on the frequencies of some of the inertial modes of this model. As a first approximation, however, we ignore the ellipticity of the core’s figure. The 3PD scheme describes the exact linearized dynamics of rotating, self-gravitating, stratified, compressible and inviscid fluids. The inertial modes of the core are the long-period free oscillations which have the Coriolis force as their restoring force. Historically an incompressible and homogeneous fluid sphere is considered to study these modes and analytical solutions are known for the frequencies and the displacement eigenfunctions of this model. We show that the effects of non-neutral density stratification may be significant, and the frequencies of these modes may change from model to model depending on the stratification parameters and the spatial structure of the modes. We further explore the role of the characteristic surfaces on the excitation and structure of these modes.
earth fluid core , inertial modes , numerical solutions , planetary interiors