Hydrodynamic instabilities in the solar tachocline
Hydrodynamic instabilities in the solar tachocline
复制标题
太阳速斜层中的流体动力学不稳定性
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
S. Tobias
中科院分区：
文献类型：
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作者：
F. Rashid;C. Jones;S. Tobias
目标。我们考虑太阳跃层的简单流体动力学模型的稳定性。这项研究只涉及非磁性不稳定性。在我们的模型中，有一个很强的径向切变，由于旋转，它与纬度温度梯度耦合。我们还假设存在一种强烈的稳定层结，适合于缓慢的塔可跃层。方法：研究方法。这些不稳定性是通过使用基于矩阵的配置法求出特征值和特征函数来计算的。我们还在相应的强稳定层结和小Prandtl数的渐近极限中找到了关键不稳定性的解析表达式。结果。我们发现了两种不同类型的不稳定性，一种是轴对称的Goldreich-Schubert模，另一种是三维Eadytype模。这两种模式都受到热扩散的影响。我们发现，在慢长跃层中，Knobloh&Spruit(1982，A&A，113,261)所考虑的轴对称模可能占主导地位。Eady类型的非轴对称斜压不稳定在靠近对流区底部的层中可能是重要的。
Aims. We consider the stability of simple hydrodynamic models of the solar tachocline. This study addresses only the non-magnetic instabilities. In our model there is a strong radial shear, which because of the rotation is coupled to a latitudinal temperature gradient. We also assume there is a strong stable stratification, appropriate for the slow tachocline. Methods. These instabilities are calculated by finding the eigenvalues and eigenfunctions using a matrix-based collocation method. We also find analytic expressions for the key instabilities in the relevant asymptotic limits of strong stable stratification and small Prandtl number. Results. We find two distinct types of instability, axisymmetric modes of the Goldreich-Schubert type, and three-dimensional Eadytype modes. Both types of mode are affected by thermal diffusion. We find that the axisymmetric modes considered by Knobloch & Spruit (1982, A&A, 113, 261) are likely to dominate in the slow tachocline. The non-axisymmetric baroclinic instability of Eady-type may be important in the layers closer to the base of the convection zone.