On the dynamical implications of models of Bs in the Earth’s core
On the dynamical implications of models of Bs in the Earth’s core
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DOI：
10.1046/j.1365-246x.1999.00909.x
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发表时间：
1999-09
影响因子：
2.8
通讯作者：
S. Zatman;J. Bloxham
中科院分区：
文献类型：
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作者：
S. Zatman;J. Bloxham
最近的研究表明，地核表面的纬向、赤道对称、随时间变化的流模型部分可以很好地用两个驻波来解释，并且通过做出某些假设，这些波可以被反演为rms Bs（远离旋转轴的场的分量）和一个参数化摩擦或波的激发（F）的量。在这里，我们讨论了两个波，并描述了均方根Bs和摩擦/激励模型对核心动态状态，轴向圆柱体上的扭矩平衡以及最近的地球发电机数值模拟的影响。我们提出了几种可能的解释，为什么只需要两个驻波来测试数据。包括这是由于堆芯流模型的分辨率而不是堆芯本身的条件的可能性。我们认为，均方根Bs和F的τ s表明，在堆芯中惯性的作用不应被忽视，在构造地球发电机模拟时应小心，以免核幔边界的有效摩擦力淹没惯性项。在地核中，两者的大小之比似乎是O（1）：我们相信，理想情况下，地核的数值模型应该重现这一结果。
SUMMARY Recent work has shown that the zonal, equatorially symmetric, time-varying part of a model of the £ow at the surface of the Earth’s core can be well explained by only two standing waves, and that by making certain assumptions these waves may be inverted for rms Bs (the component of ¢eld pointing away from the rotation axis) and a quantity parametrizing friction or excitation (F) of the waves. Here, we discuss the two-wave ¢t, and describe the implications of models of rms Bs and friction/excitation for the dynamic state of the core, for the torque balance on axial cylinders, and for recent numerical simulations of the geodynamo.We ¢nd several possible explanations for why only two standing waves are needed to ¢t the data, including the possibility that it is due to the resolution of the core £ow model rather than conditions within the core itself.We ¢nd that the ¢ts of rms Bs and F suggest that the role of inertia should not be discounted in the core, and that care should be taken in constructing geodynamo simulations so that the eiective friction at the core^mantle boundarydoes not swamp the inertial term. A ratio of the magnitude of the two appears to be O(1) in the Earth’s core: we believe that, ideally, a numerical model of the Earth’s core should reproduce this result.