Two phase flow in the Earth’s core

Earth’s solid inner core grows as the planet cools. The material in the overlying fluid outer core comprises liquid iron and lighter components, and as the iron crystallizes on the inner core, light material is released and floats upwards stirring the outer core. This convective stirring powers the geodynamo, the source of the Earth’s magnetic field. It has been known for decades that this compositional convection is the main energy source for core dynamics, but recent seismological observations indicate that a 150 km-thick layer above the inner core boundary (the F-layer) is stably stratified. This raises a fundamental question: how is light element transported from the inner core boundary to the fluid core without mixing the F-layer?
We have recently developed a slurry model of the F-layer, where solid iron particles crystallize throughout the layer. Unlike previous models the slurry explains how light element is transported across the F-layer. The main assumption of the slurry model is that the layer is at the liquidus temperature that divides solid and liquid, a constraint that has far-reaching consequences. The aim of this project is to relax this constraint and develop a new model that consistently incorporates the dynamics of melting and freezing.