全球圆柱剪切流中径向相关的大尺度动力系统和局部笛卡尔极限
Radially Dependent Large Scale Dynamos in Global Cylindrical Shear Flows and the Local Cartesian Limit
摘要：
对于圆柱形差动旋转等离子体，我们研究了大尺度磁场的产生从有限振幅非轴对称扰动通过比较数值模拟与准线性解析理论。当启动与垂直磁场的零或有限的净通量，我们的全球圆柱形模拟表现出磁旋转不稳定性（MRI）和大规模发电机增长的径向交变平均场，平均高度和方位角。这种发电机的增长解释了我们的分析计算的非轴对称波动引起的电动势是持续的方位角剪切的波动场。标准的“欧米加效应”（由微分旋转引起的平均场切变）并不重要。对于MRI的情况下，我们表示的大规模发电机场作为一个功能的差异旋转。由此产生的径向交替的大规模领域可能有影响的角动量运输磁盘和日冕。为了与以前的工作与当地线性剪切的大规模发电机，并确定所需的最小条件，大规模的字段增长，我们也解决了我们的方程在当地的笛卡尔坐标。我们发现，大规模的发电机增长的线性剪切流没有旋转可以持续剪切加上非轴对称波动-即使不是螺旋形的，一个看似以前未识别的区别。线性剪切流发电机作为我们更一般的新的全球圆柱计算的一个更受限制的版本出现。
英文摘要：
For cylindrical differentially rotating plasmas, we study large-scale magnetic field generation from finite amplitude non-axisymmetric perturbations by comparing numerical simulations with quasi-linear analytic theory. When initiated with a vertical magnetic field of either zero or finite net flux, our global cylindrical simulations exhibit the magnetorotational instability (MRI) and large scale dynamo growth of radially alternating mean fields, averaged over height and azimuth. This dynamo growth is explained by our analytic calculations of a non-axisymmetric fluctuation-induced EMF that is sustained by azimuthal shear of the fluctuating fields. The standard "Omega effect" (shear of the mean field by differential rotation) is unimportant. For the MRI case, we express the large-scale dynamo field as a function of differential rotation. The resulting radially alternating large-scale fields may have implications for angular momentum transport in disks and corona. To connect with previous work on large scale dynamos with local linear shear and identify the minimum conditions needed for large scale field growth, we also solve our equations in local Cartesian coordinates. We find that large scale dynamo growth in a linear shear flow without rotation can be sustained by shear plus non-axisymmetric fluctuations -- even if not helical, a seemingly previously unidentified distinction. The linear shear flow dynamo emerges as a more restricted version of our more general new global cylindrical calculations.
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