排斥电流通道中相互作用的倾斜和扭结不稳定性
Interacting tilt and kink instabilities in repelling current channels
摘要：
我们提出了一个电阻磁流体力学的初始平衡配置包含相邻的，相反方向的，平行的电流通道的数值研究。由于相反方向的电流通道排斥，平衡是一个理想的磁流体动力学倾斜不稳定性。这种倾斜的演变，以前在平面设置中研究，涉及两个磁岛或磁通绳，在阿尔芬时标上进行组合旋转和分离。这反过来又导致创建（近）奇异电流层，提出了严峻的挑战，数值方法。使用我们的开源网格自适应MPI-AMRVAC软件，我们重新审视了可压缩MHD中的平面演化情况，以及其扩展到2.5D和全3D场景。只要第三维度保持可伸缩性，就产生几乎不受平面外磁场分量影响的纯倾斜演变。在所有的2.5D运行中，我们的模拟确实显示了二次撕裂型中断整个近奇异电流片在远非线性饱和制度。在全3D中，两个电流通道都可能易于产生额外的理想扭结变形。我们讨论了倾斜和扭结不稳定性同时作用在暴力，重联主导的演变的影响。在3D中，倾斜和扭结不稳定性都可以通过张力来稳定。作为一个具体的空间等离子体应用，我们认为，相互作用的倾斜扭结不稳定性排斥电流通道提供了一种新的途径，启动太阳日冕物质抛射，明显不同于目前青睐的纯扭结或环面不稳定性路线。
英文摘要：
We present a numerical study in resistive magnetohydrodynamics where the initial equilibrium configuration contains adjacent, oppositely directed, parallel current channels. Since oppositely directed current channels repel, the equilibrium is liable to an ideal magnetohydrodynamic tilt instability. This tilt evolution, previously studied in planar settings, involves two magnetic islands or fluxropes, which on Alfvenic timescales undergo a combined rotation and separation. This in turn leads to the creation of (near) singular current layers, posing severe challenges to numerical approaches. Using our open-source grid-adaptive MPI-AMRVAC software, we revisit the planar evolution case in compressible MHD, as well as its extension to 2.5D and full 3D scenarios. As long as the third dimension remains ignorable, pure tilt evolutions result which are hardly affected by out of plane magnetic field components. In all 2.5D runs, our simulations do show secondary tearing type disruptions throughout the near singular current sheets in the far nonlinear saturation regime. In full 3D, both current channels can be liable to additional ideal kink deformations. We discuss the effects of having both tilt and kink instabilities acting simultaneously in the violent, reconnection dominated evolution. In 3D, both the tilt and the kink instabilities can be stabilized by tension forces. As a concrete space plasma application, we argue that interacting tilt-kink instabilities in repelling current channels provide a novel route to initiate solar coronal mass ejections, distinctly different from currently favored pure kink or torus instability routes.
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