Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany.
Proc Natl Acad Sci U S A. 2012 Mar 13;109(11):4070-3. doi: 10.1073/pnas.1111841109. Epub 2012 Feb 28.
Earth's magnetic field is sustained by magnetohydrodynamic convection within the metallic liquid core. In a thermally advecting core, the fraction of heat available to drive the geodynamo is reduced by heat conducted along the core geotherm, which depends sensitively on the thermal conductivity of liquid iron and its alloys with candidate light elements. The thermal conductivity for Earth's core is very poorly constrained, with current estimates based on a set of scaling relations that were not previously tested at high pressures. We perform first-principles electronic structure computations to determine the thermal conductivity and electrical resistivity for Fe, Fe-Si, and Fe-O liquid alloys. Computed resistivity agrees very well with existing shock compression measurements and shows strong dependence on light element concentration and type. Thermal conductivity at pressure and temperature conditions characteristic of Earth's core is higher than previous extrapolations. Conductive heat flux near the core-mantle boundary is comparable to estimates of the total heat flux from the core but decreases with depth, so that thermally driven flow would be constrained to greater depths in the absence of an inner core.
地球的磁场由金属液态内核中的磁流体动力学对流维持。在热对流的内核中，可用于驱动地球发电机的热量部分被沿核地热梯度传导的热量所减少，而核地热梯度的热导率则对内核中轻元素候选体的铁及其合金的热导率非常敏感。地球内核的热导率受到很大限制，目前的估计值基于一组扩展关系，这些关系以前没有在高压下进行过测试。我们进行了第一性原理电子结构计算，以确定 Fe、Fe-Si 和 Fe-O 液态合金的热导率和电阻率。计算出的电阻率与现有的冲击压缩测量结果非常吻合，并表现出对轻元素浓度和类型的强烈依赖性。在具有地球内核特征的压力和温度条件下的热导率高于以前的外推值。在接近核幔边界的传导热通量与核心总热通量的估计值相当，但随着深度的增加而减小，因此，如果没有内核，热驱动的流动将受到更大深度的限制。
