扩展径向自相似磁流体动力学模型的电阻喷流模拟
Resistive jet simulations extending radially self-similar magnetohydrodynamic models
摘要：
具有自相似初始和边界条件的数值模拟提供了射流动力学的理论和数值研究之间的联系。我们对Blandford & Payne类型的广义解进行轴对称电阻磁流体动力学（MHD）模拟，并将其与相应的分析和数值理想MHD解进行比较。我们解开的数值和物理扩散的影响。后者可能发生在吸积盘上方的外流中，通过MHD湍流（异常湍流扩散率）或部分电离流中的双极扩散从底层盘转移到盘冠中。我们的结论是，虽然经典的磁雷诺数$R_{\rm m}$措施的重要性，电阻效应的感应方程，一个新引入的数字，$\rbeta=(β/2)R_{\rm m}$与$β$的等离子体β，措施的重要性，电阻效应的能量方程。因此，在带有$β<2$的磁化射流中，当$\rbeta \la 1$时，电阻效应是不可忽略的，并且主要影响能量方程。所提出的模拟确实表明，对于对应于$\rbeta \ga 1$的磁扩散率的范围内的流动仍然接近理想的MHD自相似的解决方案。
英文摘要：
Numerical simulations with self-similar initial and boundary conditions provide a link between theoretical and numerical investigations of jet dynamics. We perform axisymmetric resistive magnetohydrodynamic (MHD) simulations for a generalised solution of the Blandford & Payne type, and compare them with the corresponding analytical and numerical ideal-MHD solutions. We disentangle the effects of the numerical and physical diffusivity. The latter could occur in outflows above an accretion disk, being transferred from the underlying disk into the disk corona by MHD turbulence (anomalous turbulent diffusivity), or as a result of ambipolar diffusion in partially ionized flows. We conclude that while the classical magnetic Reynolds number $R_{\rm m}$ measures the importance of resistive effects in the induction equation, a new introduced number, $\rbeta=(β/2)R_{\rm m}$ with $β$ the plasma beta, measures the importance of the resistive effects in the energy equation. Thus, in magnetised jets with $β<2$, when $\rbeta \la 1$ resistive effects are non-negligible and affect mostly the energy equation. The presented simulations indeed show that for a range of magnetic diffusivities corresponding to $\rbeta \ga 1$ the flow remains close to the ideal-MHD self-similar solution.
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