Stability of magnetic fields with differential rotation

提出这一建议的主要动机是为了解决一个令人困惑的问题，即越来越多的关于恒星结构和演化的论文依赖于非轴对称磁不稳定性，但它们的存在既不是通过实验室实验实现的，也不是通过定义良好的数值模拟实现的。计划对慢速和快速旋转影响下磁扭结型不稳定性的角动量输运和电动势进行系统的研究。对于所有的热星（包括较慢的Ap星），基本旋转可能主导了内部环面磁场（Ω≤ΩA， ΩA alfv<s:1>频率），因此快速旋转的结果是重要的，这是已知的抑制扭结型不稳定性。对于圆柱几何中0.01≤Pm≤1的磁普朗特数，已有一种非线性谱码，但其并行性有待大力改进。用它来理解非轴对称不稳定性的基本非线性饱和过程，用基本旋转速率和磁幅值来计算涡旋粘度和磁扩散系数，用密度分层和不密度分层来计算螺旋度和α-效应。我们特别感兴趣的是回答一个问题，即在考虑磁不稳定性的基础上，替代发电机模型（“泰勒-斯普瑞特发电机”）是否可能。

The key motivation for the proposal is to resolve the puzzling situation that more and more papers about stellar structure and evolution appear that rely on nonaxisymmetric magnetic instabilities, but their existence is realized neither by laboratory experiments nor by well-defined numerical simulations. A systematic study of the angular momentum transport and the electromotive force for magnetic kink-type instabilities under the influence of slow and fast rotation is planned. For all hot stars (including slower Ap stars) the basic rotation probably dominates the inner toroidal magnetic field (Ω ≤ ΩA, ΩA Alfvén frequency) so that the results for fast rotation are important which is known to suppress the kink-type instabilities. A nonlinear spectral code for magnetic Prandtl numbers 0.01 ≤ Pm ≤ 1 in cylindric geometry is existing but its parallelization must strongly be improved. It should be used to understand the basic nonlinear saturation process of the nonaxisymmetric instabilities and to calculate • the eddy viscosity and the magnetic diffusivity in terms of the basic rotation rate and the magnetic amplitude,• the resulting helicity and the α-effect with and without density stratification.Our particular interest is to answer the question whether alternative dynamo models (‘Tayler-Spruit dynamo’) are possible on the basis of the considered magnetic instabilities or not.