Thermal conductivity of iron in Earth's core is low enough to support thermal convection
Abstract
We have computed the electrical resistivity and thermal conductivity of solid and liquid iron under core conditions, including both electron-ion (electron-phonon) and electron-electron scattering [1]. We have included saturation effects [2] in different approximations. We find somewhat higher resistivity than recent resistivity measurements [3] and somewhat higher thermal conductivity than recent thermal conductivity measurements [4], and lower thermal conductivities than those that assume an ideal Wiedemann-Franz Lorenz factor and ignore electron-electron scattering [5]. We estimate an average thermal conductivity at the core mantle boundary (CMB) of 75±10 W/m/K and 120±15 W/m/K at the inner core boundary (ICB), which is consistent with the geodynamo being driven at least in part by thermal convection today, and possibly prior to inner core formation [6]. At the CMB this corresponds to a core adiabatic heat flow of about 11.4 TW for an adiabatic temperature gradient of 1 K/km. If the core cooled constantly at this rate it implies the inner core nucleated 450-650 million years ago. This work is supported by the ERC Advanced grant ToMCaT and by the Carnegie Institution for Science. The authors gratefully acknowledge the Gauss Centre for Supercomputing e.V. (www.gauss-centre.eu) for funding this project by providing computing time on the GCS Supercomputer SuperMUC at Leibniz Supercomputing Centre (LRZ, www.lrz.de). [1] Xu et al. (2018) Thermal conductivity and electrical resistivity of solid iron at Earth's core conditions from first principles, Physical Review Letters, in press, https://arxiv.org/abs/1710.03564; [2] Gomi et al. (2013) Phys. Earth Planet. Inter. 224 88; [3] Ohta et al. Nature 534 95; [4] Konopkova et al. (2016) Nature 534 99; [5] Pozzo et al. (2012) Nature 485 355. [6] Driscoll, P. E. (2016) Geophys. Res. Lett. 43 5680.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMDI43B0018C
- Keywords:
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- 1507 Core processes;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1510 Dynamo: theories and simulations;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 3924 High-pressure behavior;
- MINERAL PHYSICSDE: 7207 Core;
- SEISMOLOGY