论文标题
在三维磁流体动力学等离子体中重新访问运动学快速发电机：从非螺旋流到螺旋流的发电机过渡
Revisiting Kinematic Fast Dynamo in 3-dimensional magnetohydrodynamic plasmas: Dynamo transition from non-Helical to Helical flows
论文作者
论文摘要
在速度波动中产生的磁场的发电机是我们对几种天体物理和/或实验室现象的理解至关重要的。尽管众所周知，流体螺旋在发电机的开始中起着关键作用，但其效果尚未完全理解。在这项工作中，最近提出了流体流量[Yoshida等。物理。莱特牧师。 119，244501（2017）]被调用，以便在模拟开始时，可以使用控制参数向零或有限的流体螺旋注入零或有限的流体螺旋。使用简单的运动学快速发电机模型，我们明确地证明了短尺度发电机对流体螺旋的强烈依赖性。与常规理解相反，这表明流体螺旋性确实会强烈影响短尺度发电机的物理。为了证实我们的发现，呈现了各种注射流体螺旋性值的迟到磁场光谱，以及严格的3D磁场表面的``几何''''标志，该标志显示了从``twisted'''''''''''''''''''''''''''''''''的过渡。还表明，研究最多的ABC发电机模型之一不是``最快''发电机模型对于较低磁性雷诺数的问题。这项工作首次将流体螺旋性从系统地从``非dynamo'''转移到``dynamo''方向。
Dynamos wherein magnetic field is produced from velocity fluctuations are fundamental to our understanding of several astrophysical and/or laboratory phenomena. Though fluid helicity is known to play a key role in the onset of dynamo action, its effect is yet to be fully understood. In this work, a fluid flow proposed recently [Yoshida et al. Phys. Rev. Lett. 119, 244501 (2017)] is invoked such that one may inject zero or finite fluid helicity using a control parameter, at the beginning of the simulation. Using a simple kinematic fast dynamo model, we demonstrate unambiguously the strong dependency of short scale dynamo on fluid helicity. In contrast to conventional understanding, it is shown that fluid helicity does strongly influence the physics of short scale dynamo. To corroborate our findings, late time magnetic field spectra for various values of injected fluid helicity is presented along with rigorous ``geometric'' signatures of the 3D magnetic field surfaces, which shows a transition from ``untwisted'' to ``twisted'' sheet to ``cigar'' like configurations. It is also shown that one of the most studied ABC dynamo model is not the ``fastest'' dynamo model for problems with lower magnetic Reynolds number. This work brings out, for the first time, the role of fluid helicity in moving from ``non-dynamo'' to ``dynamo'' regime systematically.
