Experiments on Convection and Turbulence in Earth's Core

该研究项目的目标是使用实验室流体动力学模型来模拟地球液体外核中的流动。这项研究的结果将与地球物理观测和数值模型一起用于探索地球发电机的工作原理。我们将研究地球发电机中的两个重要现象。第一个问题是外核大尺度运动的起源及其与下地幔三维地震结构的关系。研究人员将根据从下地幔地震结构推断出的边界非均质性模式，对具有近径向浮力的旋转流体壳体中的对流结构进行实验研究。结果将有助于约束核地幔相互作用的性质，特别是外核对流如何受到核幔边界横向变化的条件的影响，包括变化的热流、地形和稳定的分层。这一结果应为确定地幔非均质性对地核和地球发电机长期行为的影响提供依据。第二个项目是将磁流体湍流实验室实验的测量结果应用到外核的湍流中。研究人员将进行一项实验研究，研究在均匀磁场存在的情况下，在绕射旋转的液态镓圆柱体中产生的管状现象。这种磁泰勒-库埃特流的性质将被用来估计在实验可获得的参数范围内的湍流扩散率，以便外推到地核的条件。

The goal of this research project is to simulate the flow in the Earth's liquid outer core using laboratory fluid dynamic models. The results of this study will be used, together with geophysical observations and numerical models, to probe the workings of the geodynamo. Two phenomena important in the geodynamo will be investigated. The first concerns the origin of large scale motions in the outer core and their relationshop to the three-dimensional seismic structure of the lower mantle. The investigators will study experimentally the structure of convection in rotating fluid shells with nearly radial buoyancy forces, subject to patterns of boundary heterogeneity inferred from lower mantle seismic structure. The results will help constrain the nature of core-mantly interaction, specifically how convection in the outer core is affected by the laterally variable conditions at the core-mantle boundary, including variable heat flow, topogrpahy and stable layering. The results should provide a basis for identifying effects of mantle heterogeneity on the long-term behavior of the core and the geodynamo. The second project is to apply measurements from laboratory experiments of hydromagnetic turbulent flow to turbulence in the outer core. The investigators will perform an expermental study of tutbulence generated in a diffrentially rotatin cylinder of liquid gallium in the presence of uniform magnetic fields. Properties of this magnetic Taylor-Couette flow will be used to estiate the turbulent diffusivity over the range of experimentally accessible paramenter, for extrapolation to conditions in the Earth's core.