Recent simulation and experimental results suggest that the magnetic island and flow on resonant surface often do not satisfy the "no-slip" condition in the steady state. A new theory model on nonlinear plasma response to external magnetic perturbation in absence of no-slip condition is proposed. The model is composed of the equations for the evolution of both width and phase of magnetic island due to forced reconnection driven by the external magnetic perturbation, and the force-balance equation for the plasma flow. When the island width is much less than the resistive layer width, the island growth is governed by the linear Hahm-Kulsrud-Taylor solution in presence of time-dependent plasma flow. In the other regime when the island width is much larger than the resistive layer width, the evolution of both island width and phase can be described using the Rutherford theory. The island solution is used to construct the quasi-linear electromagnetic force, which together with viscous one, contributes to the nonlinear variation in plasma flow. The no-slip condition assumed in the conventional error field theory is not imposed here, where the island oscillation frequency depends on but does not necessarily equal to the plasma flow frequency at the rational surface.
Externally applied non-axisymmetric magnetic fields such as error field and resonant magnetic perturbation (RMP) are known to influence the plasma momentum transport and flow evolution through plasma response in a tokamak, whereas the evolution of plasma response itself strongly depends on the plasma flow as well. The nonlinear interaction between the two have been captured in the conventional error field theory with a ``no-slip'' condition, which has been recently extended to allow the ``free-slip'' condition. For comparison with simulations, we solve for the nonlinear plasma response and flo…
We present a study of perpendicular subcritical shocks in a collisional laboratory plasma. Shocks are produced by placing obstacles into the super-magnetosonic outflow from an inverse wire array z-pinch. We demonstrate the existence of subcritical shocks in this regime and find that secondary shocks form in the downstream. Detailed measurements of the subcritical shock structure confirm the absence of a hydrodynamic jump. We calculate the classical (Spitzer) resistive diffusion length and show that it is approximately equal to the shock width. We measure little heating across the shock (< 10 %…
Analysis of driven dust vortex flow is presented in a weakly magnetized plasma. The 2D hydrodynamic model is applied to the confined dust cloud in a non-uniform magnetic field in order to recover the dust vortex flow driven in a conservative force field setup, in absence of any non-conservative fields or dust charge variation. Although the time independent electric and magnetic fields included in the analysis provide conservative forcing mechanisms, when the a drift based mechanism, recently observed in a dusty plasma experiment by [M. Puttscher and A. Melzer, Physics of Plasmas, 21,123704(201…
Incompressibility of Impurity Flows in Low Density TJ-II Plasmas and Comparison with Neoclassical Theory
在TJ-Ⅱ仿星器上用电荷交换复合谱（CXRS）测量了完全电离碳的极向和环向速度。我们对3D几何形状进行了详细的处理，并表明在同一通量表面的不同位置进行的流量测量与所研究的低密度等离子体的流量不可压缩性（线平均电子密度$\bar{n}_e\,\le\,10^{19}$ m $^{-3}$）兼容。此外，与新古典计算的比较表明，在没有外部动量输入的情况下，与测量的径向电场和离子自举平行流的定量协议。
A number of physical processes in laser-plasma interaction can be described with the two-fluid plasma model. We report on a solver for the three-dimensional two-fluid plasma model equations. This solver is particularly suited for simulating the interaction between short laser pulses with plasmas. The fluid solver relies on two-step Lax-Wendroff split with a fourth-order Runge-Kutta scheme, and we use the PseudoSpectral Analytical Time-Domain (PSATD) method to solve Maxwell's curl equations. Overall, this method is only based on finite difference schemes and fast Fourier transforms and does not…
Direct experimental measurement of ion properties in extreme plasma condition
University of Nevada Reno（内华达大学雷诺分校）；Indian Institute of Technology Delhi（德里印度理工学院）；Indian Institute of Science Education and Research（印度科学教育与研究学院）；Joint Institute for High Temperatures, Russian Academy of Sciences（俄罗斯科学院高温联合研究所）
We study the effect of a tangled sub-fG level intergalactic magnetic field (IGMF) on the electrostatic instability of a blazar-induced pair beam. Sufficiently strong IGMF may significantly deflect the TeV pair beams, which would reduce the flux of secondary cascade emission below the observational limits. A similar flux reduction may result from the electrostatic beam-plasma instability, which operates the best in the absence of IGMF. Considering IGMF with correlation lengths smaller than a kpc, we find that weak magnetic fields increase the transverse momentum of the pair beam particles, whic…
We report a laser-plasma experiment that was carried out at the LMJ-PETAL facility and realized the first magnetized, turbulent, supersonic plasma with a large magnetic Reynolds number ($\mathrm{Rm} \approx 45$) in the laboratory. Initial seed magnetic fields were amplified, but only moderately so, and did not become dynamically significant. A notable absence of magnetic energy at scales smaller than the outer scale of the turbulent cascade was also observed. Our results support the notion that moderately supersonic, low-magnetic-Prandtl-number plasma turbulence is inefficient at amplifying ma…
Energy partition in collisionless counterstreaming plasmas
High Energy Density Science Division, SLAC National Accelerator Laboratory（SLAC国家加速器实验室高能密度科学部）；GAP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa（里斯本大学高等技术学院等离子体与核聚火研究所GAP小组）
