On a small-scale roughness of the core-mantle boundary

The roughness of the core-mantle boundary, on the scale of centimeters to t ens of meters, is modelled using a cellular automata method. Square cells, of the size of grains of the mantle material, on a 2-D grid, can be in one of three states corresponding to mantle silicate or oxide, core fluid satur ated in light element and unsaturated core fluid. The dynamical process of evolution is defined as a stationary stochastic process without memory. Tra nsitions of doublets of cells from one state to another are governed by par ameters representing the rates of physical processes: dissolution and cryst allization at the CMB and diffusion of the light element in the core fluid. With reasonable values of the parameters, the boundary roughens on the sca le of grains, and a boundary layer of saturated fluid, of a few tens of cen timeters thick, soon appears at the interface. An undulation with dominant wavelength of the order of a few tens of meters eventually appears. An inte raction of the roughness of the CMB with the fluid flow in the core is cons idered as possible. (C) 2001 Elsevier Science B.V. All rights reserved.