论文标题
在倾斜不稳定性的非线性演化过程中，浆液链的形成和快速磁重连接
Formation of plasmoid chains and fast magnetic reconnection during nonlinear evolution of the tilt instability
论文作者
论文摘要
我们通过二维不可压缩的磁性水力动力学（MHD）数值模拟进行了研究，当Lundquist Number $ S $超过静脉链的形成所支持的快速碰撞磁重新连接方案超过了一个关键值（以磁性prandtl数字，$ p_m = 1 $）。采用了一种最近开发的特征性 - 加勒金有限元代码FinmHD，该代码专门为此目的而设计在降低的抗Visco的MHD框架中。与以前的研究相反，选择了两个排斥当前通道的不同初始设置，以便由于倾斜不稳定而在Alfvénic时间尺度上形成两个准单一电流层。如果$ s <5 \ times 10^3 $，则按照经典甜蜜模型预测的速率缩放为$ s^{ - 1/2} $，获得随后的固定重新连接过程。否则，会发生随机时间依赖的重新连接制度，其快速时间平均速率独立于$ S $，并具有0.014 $的正常化价值。后者的状态是由两个静态阶段后突然的超级alfvénic生长突然的浆液链形成的浆液形成，这与Comisso等人提出的浆细胞不稳定性的一般理论一致。 [物理。等离子体23，100702（2016）]。此外，确认了渐近地降低对数法律在无限$ s $ limit中渐近减少对数法律后，浆液增长率的非单调依赖性已得到证实。我们还将我们的结果与在合并不稳定设置的开发过程中获得的结果进行了仔细的比较，以评估机制的一般性。最后，我们简要讨论了结果的相关性，以解释太阳能电晕和Tokamaks内部破坏的爆发活动。
We investigate, by means of two-dimensional incompressible magnetohydrodynamic (MHD) numerical simulations, the fast collisional magnetic reconnection regime that is supported by the formation of plasmoid chains when the Lundquist number $S$ exceeds a critical value (at magnetic Prandtl number, $P_m = 1$). A recently developed characteristic-Galerkin finite-element code, FINMHD, that is specifically designed for this aim in a reduced visco-resistive MHD framework, is employed. Contrary to previous studies, a different initial setup of two repelling current channels is chosen in order to form two quasi-singular current layers on an Alfvénic time scale as a consequence of the tilt instability. If $S < 5 \times 10^3$, a subsequent stationary reconnection process is obtained with a rate scaling as $S^{-1/2}$ as predicted by the classical Sweet-Parker model. Otherwise, a stochastic time-dependent reconnection regime occurs, with a fast time-averaged rate independent of $S$ and having a normalized value of $0.014$. The latter regime is triggered by the formation of two chains of plasmoids disrupting the current sheets with a sudden super-Alfvénic growth following a quiescent phase, in agreement with the general theory of the plasmoid instability proposed by Comisso et al. [Phys. Plasmas 23, 100702 (2016)]. Moreover, the non-monotonic dependence of the plasmoid growth rate with $S$ following an asymptotically decreasing logarithmic law in the infinite $S$-limit is confirmed. We also closely compare our results to those obtained during the development of the coalescence instability setup in order to assess the generality of the mechanism. Finally, we briefly discuss the relevance of our results to explain the flaring activity in solar corona and internal disruptions in tokamaks.
