Electrical conductivity in the mantle and core and implications for the geodynamo

Abstract:

Earth's magnetic field was believed to arise from thermal convection of molten iron alloy in Earth's outer core, but density functional theory (DFT) calculations suggested that the conductivity of iron is too high to support thermal convection, so that new geodynamo models were being developed. These DFT calculations considered the resistivity that arises from electrons scattering off of vibrating atoms (called electron-phonon scattering). It was believed since the 1930's that this would be the main contribution to electrical resistivity in metals. We find that electron scattering off of other electrons is just as important as electron-phonon scattering, and this brings the predicted transport properties of iron into agreement with geophysical estimates, and allows thermal convection to drive the geodynamo. Experiments at core conditions are extremely difficult, and transport properties in metals have considered mainly conventional electron-phonon processes at high temperatures. Other recent work will be reviewed and discussed. This work is supported by NSF and by the ERC Advanced grant ToMCaT.