论文标题
在大磁性prandtl数字上积聚盘中的MRI湍流
MRI turbulence in accretion discs at large magnetic Prandtl numbers
论文作者
论文摘要
大型磁性prandtl数字$ \ text {pm} $（粘度与电阻率的比率）对磁化不稳定性（MRI）的湍流传输和能量学的影响，尽管在天体物理环境中认识到这种情况下的这种状态，但从二元中性群体中，X-Recient and sar x-Ray necimions and x-Ray necimions and necimions and x-Ray necimions disparate，尽管这是X-Rectiment and x-rais x-Ray necimions x-ray neciment and x-rasion x-rasion x-rasion and x-rasion nectim，原子星的内部。我们通过使用有限量代码\ textsc {pluto}进行完全可压缩的3D MHD剪切盒模拟，研究了制度$ \ text {pm}> 1 $中的MRI Dynamo和相关的湍流，主要集中在Keplerian Shear与Asprecretion Discs相关的情况下。我们发现，当磁性雷诺数保持固定时，动荡的传输（由$α$参数为$α$，压力与热压的比率）缩放为磁性prandtl数字为$α\ sim \ sim \ sim \ text {pm}^Δ$，$δ\ sim 0.5-0.7 $ 0.5-0.7 $ to $ \ $ \ $ \ text pm pm {pm} $ sim {$ sim} $ 128 $ 128 $} 128 $。但是，随着磁性雷诺数的增加，这种缩放会减弱。重要的是，与以前的研究相比，我们在非常大的$ \ text {pm} $上发现了一种新效果 - 湍流的能量和压力开始平稳，不再取决于$ {\ rm pm} $。为了了解这些结果，我们已经对傅立叶空间中的湍流动力学进行了详细的分析，重点是增加$ \ text {pm} $对横向级联反应的效果，这是由盘剪切流动引起的关键非线性过程，该过程是由负责MRI湍流的负责。最后，我们发现$α$ - $ \ text {pm} $缩放对框垂直到宽宽比以及背景剪切敏感。
The effect of large magnetic Prandtl number $\text{Pm}$ (the ratio of viscosity to resistivity) on the turbulent transport and energetics of the magnetorotational instability (MRI) is poorly understood, despite the realization of this regime in astrophysical environments as disparate as discs from binary neutron star mergers, the inner regions of low mass X-ray binaries and active galactic nuclei, and the interiors of protoneutron stars. We investigate the MRI dynamo and associated turbulence in the regime $\text{Pm}>1$ by carrying out fully compressible, 3D MHD shearing box simulations using the finite-volume code \textsc{PLUTO}, focusing mostly on the case of Keplerian shear relevant to accretion discs. We find that when the magnetic Reynolds number is kept fixed, the turbulent transport (as parameterized by $α$, the ratio of stress to thermal pressure) scales with the magnetic Prandtl number as $α\sim \text{Pm}^δ$, with $δ\sim 0.5-0.7$ up to $\text{Pm} \sim 128$. However, this scaling weakens as the magnetic Reynolds number is increased. Importantly, compared to previous studies, we find a new effect at very large $\text{Pm}$ -- the turbulent energy and stress begin to plateau, no longer depending on ${\rm Pm}$. To understand these results we have carried out a detailed analysis of the turbulent dynamics in Fourier space, focusing on the effect of increasing $\text{Pm}$ on the transverse cascade -- a key non-linear process induced by the disc shear flow that is responsible for the sustenance of MRI turbulence. Finally, we find that $α$-$\text{Pm}$ scaling is sensitive to the box vertical-to-radial aspect ratio, as well as to the background shear.
