Current driven rotating kink mode in a plasma column with a non-line-tied free end

Experimental Identification of the Kink Instability as a Poloidal Flux Amplification Mechanism for Coaxial Gun Spheromak Formation

The magnetohydrodynamic kink instability is observed and identified experimentally as a poloidal flux amplification mechanism for coaxial gun spheromak formation. Plasmas in this experiment fall into three distinct regimes which depend on the peak gun current to magnetic flux ratio, with (I) low values resulting in a straight plasma column with helical magnetic field, (II) intermediate values leading to kinking of the column axis, and (III) high values leading immediately to a detached plasma. Onset of column kinking agrees quantitatively with the Kruskal-Shafranov limit, and the kink acts as …

Phase control of a z-current driven plasma column

A dynamic mitigation is presented for sausage and kink instability growths of a z-current driven magnetized plasma column. We have proposed a dynamic mitigation method based on a phase control to smooth plasma non-uniformities and to mitigate the instability growth in perturbed plasma systems. In this paper we found that a wobbling motion of the z-current electron axis induces a phase-controlled perturbation, so that the growths of the sausage and kink instabilities are successfully mitigated. In general, plasma instabilities emerge from perturbations, and the perturbation phase is normally un…

安全第一：磁化冕中线系无力磁通管的稳定性与耗散

Safety first: Stability and dissipation of line-tied force-free flux tubes in magnetized coronae

本文通过线性分析和含时无力电动力学模拟，研究线系无力磁通管在不同扭转量下的稳定性与能量耗散，发现安全因子q≤1时扭曲模主导耗散，并给出增长率与特征螺距的标度关系及其对磁星磁层耗散的影响。

On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun

Measurements of the various plasma configurations produced by a planar magnetized coaxial gun provide insight into the magnetic topology evolution resulting from magnetic helicity injection. Important features of the experiments are a very simple coaxial gun design so that all observed geometrical complexity is due to the intrinsic physical dynamics rather than the source shape and use of a fast multiple-frame digital camera which provides direct imaging of topologically complex shapes and dynamics. Three key experimental findings were obtained: (1) formation of an axial collimated jet [Hsu an…

Effects of Line-tying on Magnetohydrodynamic Instabilities and Current Sheet Formation

An overview of some recent progress on magnetohydrodynamic stability and current sheet formation in a line-tied system is given. Key results on the linear stability of the ideal internal kink mode and resistive tearing mode are summarized. For nonlinear problems, a counterexample to the recent demonstration of current sheet formation by Low \emph{et al}. [B. C. Low and Å. M. Janse, Astrophys. J. \textbf{696}, 821 (2009)] is presented, and the governing equations for quasi-static evolution of a boundary driven, line-tied magnetic field are derived. Some open questions and possible strategies to…

拱形、线 tying 磁通量绳中失败环面机制的实验室研究

Laboratory study of the failed torus mechanism in arched, line-tied, magnetic flux ropes

本研究借助MRX实验的足点电流与能量分布新诊断，揭示失败环面事件可由理想MHD效应解释，并提出仅需电极薄层非理想效应的新模型。