Plasmoid Instability in the Multiphase Interstellar Medium
Plasmoid Instability in the Multiphase Interstellar Medium
复制标题
DOI：
10.3847/2041-8213/accf1f
复制
发表时间：
2022-11
期刊：
影响因子：
--
通讯作者：
D. Fielding;B. Ripperda;A. Philippov
中科院分区：
文献类型：
--
作者：
D. Fielding;B. Ripperda;A. Philippov
在湍流星际介质(ISM)中，控制复杂的团块结构、相分布和磁场几何形状的过程仍然不清楚。利用对热不稳定湍流系统进行的前所未有的高分辨率三维磁流体力学模拟，我们发现大电流片不稳定到等离子体介导的重联在整个体积中规则地形成。质团在三个不同的环境中形成：(I)在冷团中，(Ii)在冷相和暖相的不对称界面上，和(Iii)在温暖的体积填充阶段。结果表明，这种复杂的磁热相结构以高度磁化的冷相为主，但作为重联位置的高磁曲率区域的温度范围很宽。此外，我们还发现，热不稳定性改变了湍流磁场随尺度变化的各向异性，从而减小了小尺度涡旋伸长的增加。最后，我们证明了大多数质量包含在一个连续的冷结构中，周围环绕着遵循无标度质量分布的较小的团块。这些团块倾向于高度拉长，并表现出与超音速湍流一致的尺寸与内部速度关系，以及与亚音速运动一致的相对团块距离-速度标度。我们讨论了冷等离子体与观测到的微尺度原子和电离结构以及HI纤维的惊人相似性，并考虑了等离子体的存在将如何改变带电粒子的运动，从而影响ISM和其他类似系统中的宇宙线输运和热传导。
The processes controlling the complex clump structure, phase distribution, and magnetic field geometry that develop across a broad range of scales in the turbulent interstellar medium (ISM) remain unclear. Using unprecedentedly high-resolution 3D magnetohydrodynamic simulations of thermally unstable turbulent systems, we show that large current sheets unstable to plasmoid-mediated reconnection form regularly throughout the volume. The plasmoids form in three distinct environments: (i) within cold clumps, (ii) at the asymmetric interface of the cold and warm phases, and (iii) within the warm, volume-filling phase. We then show that the complex magnetothermal phase structure is characterized by a predominantly highly magnetized cold phase, but that regions of high magnetic curvature, which are the sites of reconnection, span a broad range in temperature. Furthermore, we show that thermal instabilities change the scale-dependent anisotropy of the turbulent magnetic field, reducing the increase in eddy elongation at smaller scales. Finally, we show that most of the mass is contained in one contiguous cold structure surrounded by smaller clumps that follow a scale-free mass distribution. These clumps tend to be highly elongated and exhibit a size versus internal velocity relation consistent with supersonic turbulence and a relative clump distance–velocity scaling consistent with subsonic motion. We discuss the striking similarity of cold plasmoids to observed tiny-scale atomic and ionized structures and H i fibers and consider how the presence of plasmoids will modify the motion of charged particles, thereby impacting cosmic-ray transport and thermal conduction in the ISM and other similar systems.