The anisotropy of local turbulence in the Earth's core

摘要

The anisotropy of local turbulence in the Earth's core is examined. It is recognized that small-scale motions in the core are strongly influenced by the Earth's rotation and its magnetic field. A small region of the core is simulated (the computational box), across which the prevailing large-scale (toroidal) magnetic field is supposed to be uniform and in which the temperature or compositional gradient providing the buoyancy that powers the turbulence is parallel to the (uniform) gravitational field. The simulations are used to estimate the turbulent fluxes of mean fields and their dependence on the latitude at which the computational box is situated. It is found that the effect of local turbulence on the diffusion of large-scale fields is significant, and that turbulent transport is anisotropic. It is believed that the results of the present study will prove useful in determining geophysically realistic diffusivities for use in future global geodynamo simulations.