Effects of Topographic Boundary Heterogeneity on Earth's Core Dynamics

长期以来，研究人员一直认为地核过程发生在近乎完美的球形壳内，这种情况足以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，核幔边界包含形状和温度的变化，形成了一个非均质边界。最近的模型表明，边界非均质性可能既控制着地球磁场的大规模产生（例如，Christensen和Olson， 2003），也控制着地幔和地核之间角动量的交换（例如，Hide,1969; Jault, 2003）。事实上，非均质边界的影响可能是影响地核过程的最重要的控制因素之一。然而，很少有实验室实验研究热非均质性的影响（Sumita和Olson, 1999; 2002），也没有研究地形非均质性的影响。在这项研究中，研究人员将使用耦合实验室和数值实验来测量非均匀边界地形对岩心流动的影响。结果将允许测试岩心流动是否会被地形起伏锁定。他们还将利用我们的结果来估计地核-地幔边界的粘性和压力扭矩，这些扭矩影响地球的自转和日长的变化（Jault和Lemouel， 1989年，1999年；Kuang和Bloxham， 1993年；Kuang和Chao， 2001年）。

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).