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模拟地球液态外核的流动。 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测地球发电机的工作原理。 将研究地球发电机中的两个重要现象。 第一个问题涉及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不均匀性模式，对具有近径向浮力的旋转流体壳中的对流结构进行实验研究。 这些结果将有助于限制核幔相互作用的性质，特别是外核的对流如何受到核幔边界横向可变条件的影响，包括可变热流、地形和稳定分层。 研究结果为确定地幔非均匀性对岩心和地球发电机长期行为的影响提供了依据。 第二个项目是将磁流体湍流实验室实验的测量结果应用于外核的湍流。 研究人员将对在均匀磁场存在下液体镓的差动旋转圆柱体中产生的湍流进行实验研究。 这种磁泰勒-库埃特流的特性将被用来估计在实验可获得的参数范围内的湍流扩散率，外推到地球核心的条件。

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.