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首页> 外文期刊>Geophysical and Astrophysical Fluid Dynamics >The alpha-effect in 2D fast dynamos
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The alpha-effect in 2D fast dynamos

机译:二维快速发电机中的alpha效果

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We look at the large-scale dynamo properties of spatially periodic, time dependent, helical 2D flows of the form u(x, t)=(partial derivative(y) Psi(x, y, t), -partial derivative(x) Psi(x, y, t), - (x, y, t). These flows act as kinematic fast dynamos and are able to generate a mean magnetic field uniform and constant in the xy-plane but whose direction varies periodically along z with wavenumber k. Using Mean Field Electrodynamics, the generation mechanism can be understood in terms of a k-dependent alpha-effect, which depends on the magnetic Reynolds number, R-m. We calculate this effect for different motions and investigate how its limit as k -> 0 depends on R-m and on the properties of the flows such as their spatial structure or correlation time. This work generalises earlier studies based on 2D steady flows to motions with time dependence.
机译:我们看一下形式为u(x,t)=(偏导数(y)Psi(x,y,t),-偏导数(x)的空间周期,时间相关,螺旋二维流的大规模发电机特性Psi(x,y,t),-(x,y,t)。这些流动起运动学的快速动力作用,能够在xy平面上产生均匀且恒定的平均磁场,但是其方向沿z周期性变化使用平均场电动力学,可以根据依赖于k的阿尔法效应来理解产生机理,该效应取决于磁雷诺数Rm。我们针对不同的运动计算该效应,并研究其极限为k- > 0取决于Rm以及流的属性(例如其空间结构或相关时间),这项工作概括了基于2D稳定流到具有时间依赖性的运动的早期研究。

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