Variational Approach to Free Motion in the Earth's Fluid Outer Core

Abstract

AbstractThis study is based on the elasto‐gravitational motion equations for a hydrostatic equilibrium Earth. The relative rotation among the solid elastic mantle, the fluid outer core and the solid elastic inner core is governed by the angular momentum equation. The deformation response of the mantle and inner core to the core dynamics, generated by the perturbations on the boundaries of the fluid outer core, is considered on the assumption of spherical symmetry and employed to constrain the movement on the boundaries of the fluid outer core. Based on the general symmetrical characteristics of the Earth's eigenmodes, the variational principle of free oscillations in a rotating, inviscid and elliptically stratified fluid outer core is developed and the corresponding functional is deduced.