Electrical resistivity and thermal conductivity of liquid Fe alloys at high P and T, and heat flux in Earth's core
Electrical resistivity and thermal conductivity of liquid Fe alloys at high P and T, and heat flux in Earth's core
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DOI：
10.1073/pnas.1111841109
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发表时间：
2012-03-13
影响因子：
11.1
通讯作者：
Vlcek, Vojtech
中科院分区：
文献类型：
--
作者：
de Koker, Nico;Steinle-Neumann, Gerd;Vlcek, Vojtech
地球的磁场是由金属液核内的磁流体动力学对流维持的。在热平流核中，可用于驱动地球发电机的热的部分被沿核地热沿着传导的热减少，这敏感地取决于液态铁及其具有候选轻元素的合金的热导率。地球核心的热导率受到的限制非常少，目前的估计是基于一组以前没有在高压下测试过的比例关系。我们进行第一性原理电子结构计算，以确定铁，Fe-Si，和Fe-O液态合金的热导率和电阻率。计算电阻率同意非常好，与现有的冲击压缩测量，并显示出强烈的依赖轻元素的浓度和类型。在压力和温度条件下，地球核心的热导率特征高于以前的推断。核幔边界附近的传导热通量与来自地核的总热通量的估计值相当，但随着深度的增加而减少，因此在没有内核的情况下，热驱动流将被限制在更深的深度。
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.