Interacting vorticity waves as an instability mechanism for magnetohydrodynamic shear instabilities
Interacting vorticity waves as an instability mechanism for magnetohydrodynamic shear instabilities
复制标题
相互作用涡旋波作为磁流体动力剪切不稳定性的不稳定机制
DOI：
10.1017/jfm.2015.47
复制
发表时间：
2014
影响因子：
3.7
通讯作者：
O. Umurhan
中科院分区：
文献类型：
--
作者：
E. Heifetz;J. Mak;J. Nycander;O. Umurhan
摘要：剪切流不稳定性的相互作用涡度波形式在此扩展到磁流体动力学 (MHD) 设置，为通过背景磁场的存在稳定和破坏剪切不稳定性提供机械描述。这种解释依赖于局部涡度异常引起非局部速度场，从而导致远距离作用。这里表明，系统支持的波能够通过洛伦兹力传播涡度，并且波可能相互作用。不稳定性的存在取决于基本状态的选择是否允许通过相互相互作用实现涡度波的锁相和相长干涉。为了证实这一说法，我们解决了两种代表性基本状态的不稳定性问题，一种是背景磁场稳定不稳定流，另一种是场使稳定流不稳定，并进行了相关分析以展示该机制在 MHD 中的运作方式。
Abstract The interacting vorticity wave formalism for shear flow instabilities is extended here to the magnetohydrodynamic (MHD) setting, to provide a mechanistic description for stabilising and destabilising shear instabilities by the presence of a background magnetic field. The interpretation relies on local vorticity anomalies inducing a non-local velocity field, resulting in action at a distance. It is shown here that the waves supported by the system are able to propagate vorticity via the Lorentz force, and waves may interact. The existence of instability then rests upon whether the choice of basic state allows for phase locking and constructive interference of the vorticity waves via mutual interaction. To substantiate this claim, we solve the instability problem of two representative basic states, one where a background magnetic field stabilises an unstable flow and the other where the field destabilises a stable flow, and perform relevant analyses to show how this mechanism operates in MHD.