Transport properties of liquid metals and viscosity of the Earth's core

Coefficients expressing transport properties of liquid metals (viscosity and diffusivity) can be scaled to the absolute melting temperature. A systematic review of the published experimental data leads to the conclusion that the effect of pressure on viscosity and diffusivity can be taken into account through its effect on the melting temperature. Hence, the viscosity and diffusivity at the melting temperature are constants for a given metal. The viscosity of the Earth's liquid core, near the inner core boundary, is probably close to that of liquid iron at ambient pressure, namely 6 cP (centipoises). The viscosity profile in the fluid core has been calculated. Using the same approach for the effect of impurities, it is suggested that the diffusivity of sulphur in the core is probably of the order of 10−4 cm2 s−1.