MRI通道流及其寄生流
MRI channel flows and their parasites
摘要：
局部模拟吸积盘中的磁旋转不稳定性（MRI）可以显示出称为通道流的循环相干结构。这些结构的形成和破坏可能在MRI引起的湍流的发展和饱和中发挥作用，从而帮助我们了解某些天体的吸积行为随时间的变化。以前的研究表明，信道的解决方案受到各种寄生模式，其中最重要的是一个类似的开尔文-亥姆霍兹不稳定性的攻击。我们重新审视这些不稳定性，并展示它们如何与等离子体物理的经典不稳定性，扭结和捏模式。然而，我们认为，在大多数情况下，通道出现发达的湍流，并最终被破坏的湍流混合，而不是由寄生虫。例外情况是出现在接近临界的系统中或从低振幅初始条件出现的干净的孤立通道。这些结构不可避免地达到大振幅，然后才被破坏，引起爆发行为。
英文摘要：
Local simulations of the magnetorotational instability (MRI) in accretion disks can exhibit recurrent coherent structures called channel flows. The formation and destruction of these structures may play a role in the development and saturation of MRI-induced turbulence, and consequently help us understand the time-dependent accretion behaviour of certain astrophysical objects. Previous investigations have revealed that channel solutions are attacked by various parasitic modes, foremost of which is an analogue of the Kelvin-Helmholtz instability. We revisit these instabilities and show how they relate to the classical instabilities of plasma physics, the kink and pinch modes. However, we argue that in most cases channels emerge from developed turbulence and are eventually destroyed by turbulent mixing, not by the parasites. The exceptions are the clean isolated channels which appear in systems near criticality or which emerge from low amplitude initial conditions. These structures inevitably achieve large amplitudes and are only then destroyed, giving rise to eruptive behaviour.
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