CONVECTIVE MODES IN A TWO-LAYER APPROXIMATION OF THE EARTH'S MANTLEB. I. Birger, A. T. Ismail-zadeh, and B. M. Naimark
We present a numerical analysis of thermoconvective cell layering for the case where the thickness of the upper mantle is 3 times less than that of the lower mantle. This is more adequate than the case of two layers equal in depth assumed by Richter and Johnson in 1974. They stated that a two-tiered cell structure appears in a system of two chemically distinct layers when the density of the lower layer is only slightly greater (even 1\%) than the density of the upper layer. We produce a stability diagram on the plane of Rayleigh number and dimensionless density contrast. We show that in the case under study a four-tiered convection structure with one cell in the upper layer and three cells in the lower layer is more preferable.