论文标题
通过无电流螺旋磁场对超旋转泰勒 - 库特流动的不稳定
Destabilization of super-rotating Taylor-Couette flows by current-free helical magnetic fields
论文作者
论文摘要
在较早的论文中，我们表明，如果磁性pm \ pm pm \ neq 1 $，则方位角磁场和导电流量中的超级旋转的组合可能是不稳定的。在这里，我们证明，根据边界条件，添加弱轴向场成分可以允许轴对称扰动模式以$ pm $ $ $ unity的不同。仅对于阶统一的磁性马赫数（Azimuthal场的磁性马赫数）出现，而非轴对称模式则需要更高的值。与旋转期相比，轴对称模式的不稳定性的典型生长时间和轴向模式轴向迁移的特征时间尺度长，但与磁扩散时间相比短。这些模式根据$ b_qudb_z $的符号以正$ z $ - 方向行驶。我们还证明，如果$ | b_ϕ | \ gg | b_z | $，与旋转定律的形式无关，流动和场扰动的方位角成分在相位流动。在薄间隙的短波近似中，还显示了（在附录中），对于{\ em Ideasal}流体，所考虑的螺旋磁化不稳定性（HMRI）仅存在用于负剪切的旋转定律。
In an earlier paper we showed that the combination of azimuthal magnetic fields and super-rotation in Taylor-Couette flows of conducting fluids can be unstable against non-axisymmetric perturbations if the magnetic Prandtl number of the fluid is $Pm\neq 1$. Here we demonstrate that the addition of a weak axial field component may allow axisymmetric perturbation patterns for $Pm$ of order unity depending on the boundary conditions. The axisymmetric modes only occur for magnetic Mach numbers (of the azimuthal field) of order unity, while higher values are necessary for non-axisymmetric modes. The typical growth time of the instability and the characteristic time scale of the axial migration of the axisymmetric mode are long compared with the rotation period, but short compared with the magnetic diffusion time. The modes travel in the positive or negative $z$-direction along the rotation axis depending on the sign of $B_ϕB_z$. We also demonstrate that the azimuthal components of flow and field perturbations travel in phase if $|B_ϕ|\gg |B_z|$, independent of the form of the rotation law. Within a short-wave approximation for thin gaps it is also shown (in an Appendix) that for {\em ideal} fluids the considered helical magnetorotational instability (HMRI) only exists for rotation laws with negative shear.
