Rotational modes of a two layer stratified fluid core model

Monday, 15 December 2014
Behnam Seyed-Mahmoud1, Hossein Naseri1 and Mian Zhang2, (1)University of Lethbridge, Lethbridge, AB, Canada, (2)Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, China
We study the inertial modes of a self gravitating, stratified and inviscid two layer fluid core model with a large density jump at the boundary interface. We show that the inertial modes may be excited in each layer independently and that the displacement eigenvectors are larger in the inner component with higher density, yet there may be momentum exchange between the layers depending on the spatial structure of the excited modes. In the figure we show the displacement patterns for the (a) (3,2,1) mode in the two layer core, (b) (3,2,1) mode in the inner core, (c) (3,2,1) mode in the outer core, and (d) the (2,1,1) mode, known as the tilt over mode, in the two layer core. We also study the inertial modes of a core model which includes an elastic solid inner core in order to investigate the effects of elastic boundary at the inner boundary interface on the frequencies and the displacement eigenfunctions of these modes. The novelty of the approach is in the manner the boundary conditions are applied, especially at the interface, for a Galerkin formulation of the governing equations.