The convection current hypothesis
The convection current hypothesis
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DOI：
10.1029/rg002i001p00089
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发表时间：
1964-02
影响因子：
25.2
通讯作者：
L. Knopoff
中科院分区：
文献类型：
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作者：
L. Knopoff
本文讨论了几种地幔模型的线性稳定性问题。对于地幔物理参数的适当值，地幔对流的瑞利数似乎可能远远超过边缘不稳定所需的值。对于非常高的瑞利数的模型中的速度可以从湍流对流的解决方案。但即使瑞利数很高，布伦C区的不均匀性也足够强，足以阻止地幔对流的发生，无论这种不均匀性是相变还是化学不均匀性。还考虑了较小尺度的对流。上地幔可能发生对流。这些事件并不广泛，规模较小，横向范围约为1 200 - 1 500公里，深度约为400公里。大瑞利数和相关的湍流对流不排除下地幔。这些结论主要取决于地幔粘度和强度的假设。下地幔中的湍流对流模型与上地幔中的高强度和高粘度物质的局部化以及下地幔中没有观察到地震的观察是一致的。
The linear stability problem for a number of models of the mantle of the earth is considered. For appropriate values of the physical parameters of the mantle it seems likely that the Rayleigh number for mantle-wide convection is far in excess of the value necessary for marginal instability. For very high Rayleigh numbers the velocities in the models can be derived from solutions for turbulent convection. But even for very high Rayleigh numbers the inhomogeneity in Bullen's region C is amply strong enough to prevent mantle-wide convection from occurring, whether the inhomogeneity involves a phase transition or represents a chemical inhomogeneity. Convection on a smaller scale is also considered. Convection in the upper mantle may occur. These events are not widespread and are of small scale, having dimensions of about 1200–1500 km in lateral extent and depths of the order of 400 km. Large Rayleigh numbers and associated turbulent convection are not ruled out for the lower mantle. The conclusions depend crucially on the assumptions of the values of the viscosity and of the strength of the mantle. The model of turbulent convection in the lower mantle is consistent with localizing a material of high strength and high viscosity in the upper mantle and with the observation that earthquakes are not observed to occur in the lower mantle.