Effects of Topographic Boundary Heterogeneity on Earth's Core Dynamics

长期以来，研究人员一直认为地球的核心过程发生在一个近乎完美的球壳内，这种情况有助于解释大多数大地测量和地磁观测。 然而，地震调查和地幔对流模拟表明，核幔边界包含的形状和温度的变化，创建一个不均匀的边界。最近的模型表明，边界不均匀性可能控制着地球磁场的大规模产生（例如，Christensen和Olson，2003年）和地幔与地核之间的角动量交换（例如，Hide，1969; Jault，2003）。 事实上，非均匀边界效应可能是影响地核过程的最重要的控制因素之一。然而，有很少的实验室实验已经进行了研究的热不均匀性的影响（Sumita和Olson，1999年; 2002年）和没有研究的地形不均匀性的影响，在这项研究中，研究人员将测量不均匀边界地形对核心流的影响，使用耦合实验室和数值实验。 结果将允许测试核心流是否可以被地形隆起锁定在适当的位置。他们还将利用我们的结果来估计核幔边界处的粘性和压力力矩，这些力矩影响地球的自转和白天的长度变化（Jault和Lemouel，1989，1999; Kuang和Bloxham，1993;Kuang和Chao，2001）。

Researchers have long assumed that Earth's core processes occur withina nearly perfect spherical shell and that this condition is sufficientto explain most of the geodetic and geomagnetic observations. However,seismic investigations and mantle convection simulations suggest thatthe core-mantle boundary contains variations in shape and temperature,creating a heterogeneous boundary. Recent models suggest that boundaryheterogeneities may control both the large-scale generation of theEarth's magnetic field (e.g., Christensen and Olson, 2003) and theexchange of angular momentum between the mantle and core (e.g., Hide,1969; Jault, 2003). In fact, the effects of heterogeneous boundariesmay be one of the most important controlling factors influencingEarth's core processes. However, there are few laboratory experimentsthat have been conducted to study the effects of thermal heterogeneity(Sumita and Olson, 1999; 2002) and none to study the effects oftopographic heterogeneity.In this study, the investigators will measure the effects of heterogeneousboundary topography on core flows, using coupled laboratory and numericalexperiments. The results will allow a test of whether core flow canbecome locked in place by topographic bumps. They will also use ourresults to estimate the viscous and pressure torques at the core-mantleboundary, which affect the rotation of the Earth and variations in thelength of day (Jault and Lemouel, 1989, 1999; Kuang and Bloxham, 1993;Kuang and Chao, 2001).