COMPOSITIONAL CONVECTION AND STRATIFICATION OF EARTHS CORE
COMPOSITIONAL CONVECTION AND STRATIFICATION OF EARTHS CORE
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DOI：
10.1038/289393a0
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发表时间：
1981-01-01
期刊：
影响因子：
64.8
通讯作者：
LOPER, DE
中科院分区：
文献类型：
--
作者：
FEARN, DR;LOPER, DE
传统上，对地球外核可能分层的研究1，2一直基于热浮力，而成分的影响被隐含地忽略了。然而，最近的工作3，4已经证明了组成浮力在提供维持地球发电机所需的动力方面的重要性。因此，成分的影响在决定岩芯分层方面似乎也很重要。在这里，我们提出了一个研究的相对重要性的核心热和成分浮力。我们简要地回顾了这样一种观点，即富铁内核的生长导致铁耗尽的物质释放，因此具有浮力。然后，我们计算密度分布，如果这种轻的材料和潜热释放的内核增长是通过扩散重新分配的结果。据发现，不仅是成分的影响很重要，他们占主导地位的热效应，在确定分层的核心。最后，使用相关的核心参数估计，我们表明，扩散密度分布是不稳定的整个外核，除了一层约70公里深的地幔-核边界附近。因此，我们预计对流充满了整个外核，可能除了幔核边界以下的薄层。
Traditionally, studies1,2of the possible stratification of the outer core of the Earth have been based on thermal buoyancy, with the effects of composition being implicitly ignored. However, recent work3,4has demonstrated the importance of compositional buoyancy in providing the power necessary to sustain the geodynamo. It seems likely, therefore, that the effects of composition are also important in determining the stratification of the core. We present here a study of the relative importance of thermal and compositional buoyancy in the core. We briefly review the idea that the growth of an iron-rich inner core leads to the release of material which is depleted in iron and therefore buoyant. We then calculate the density profile which results if both this light material and the latent heat released as the inner core grows are redistributed by diffusion. It is found that not only are compositional effects important, they dominate thermal effects in determining the stratification of the core. Finally, using parameter estimates relevant to the core, we show that the diffusive density profile is unstable throughout the outer core except for a layer some 70 km deep adjacent to the mantle–core boundary. We therefore expect that convection fills the entire outer core with the possible exception of a thin layer below the mantle–core boundary.