Non-solitonic examples of the application of geometrical and topological methods in plasma physics and magnetohydrodynamics (MHD) are given. The first example considers the generalization of magnetic helicity to gravitational torsion loop. The second example considers also the application of this same torsion loop metric to some problems of helical fields in MHD dynamo theory. In the last example a Riemannian magnetic metric is given where the magnetic field itself is present in the diagonal time-independent metric. In this example the MHD equations are shown to be compatible to the geometrical Bianchi identity by making use of Cartan's differential calculus formalism. The Riemann curvature of the helical flow is also obtained.
The core collapse events observed in a stellarator experiment are studied by a three-dimensional nonlinear MHD simulations. In the low magnetic shear configuration like the Wendelstein 7-X, the rotational transform profile is very sensitive to the toroidal current density. The 3D equilibrium with localized toroidal current density is studied. If the toroidal current density follows locally in the middle of the plasma minor radius, the rotational transform is also changed locally. Sometimes, the magnetic topology changes due to appearing the magnetic island. The nonlinear behaviors of the MHD i…
The 3-D exact analytical solutions of ideal two fluid plasma, single fluid plasma (MHD) and neutral fluid equations have been found using physically justifiable assumptions. Surprisingly these solutions satisfy all non-linearities in the systems. It is pointed out that these solutions explain the fundamental mechanism behind the creation of vast variety of ordered structures in plasmas and fluids. In the limiting case of two dimensional (2-D) dependence of fields, the theoretical model for plasma is applied to explain the formation of spicules in solar chromosphere. It is pointed out that the …
In this work, several key scaling laws of the quasi-static magnetic compression of field reversed configuration (FRC) plasma [Spencer, Tuszewski, and Linford, 1983] are amended from a series of 2D FRC MHD equilibriums numerically obtained using the Grad-Shafranov equation solver NIMEQ. Based on the new scaling for the elongation and the magnetic fields at the separatrix and the wall, the empirically stable limits for the compression ratio, the fusion gain, and the neutron yield are evaluated, which may serve as a more accurate estimate for the upper ceiling of performance from the magnetic com…
We provide a procedure for identification of dominating compressible and Alfvenic MHD modes or isotropic turbulence in synchrotron emission polarization maps of Galactic objects. The results for the region of North Galactic Pole, Orion molecular cloud complex and the star-forming complex Cygnus X are presented.
Formulation and verification of multiscale gyrokinetic simulation of kinetic-MHD processes in toroidal plasmas
UC Irvine（加州大学尔湾分校）；Chinese Academy of Sciences（中国科学院）；KAIST（韩国科学技术院）；Aix-Marseille Université（艾克斯-马赛大学）；University of California, San Diego（加州大学圣地亚哥分校）；University of Science and Technology of China（中国科学技术大学）；Peking University（北京大学）
Energetic particle (EP) driven instabilities will be of strongly increased relevance in future burning plasmas as the EP pressure will be very large compared to the thermal plasma. Understanding the interaction of EPs and bulk plasma is crucial for developing next-generation fusion devices. In this work, the JOREK MHD code is extended to allow for the simulation of EP instabilities at high EP pressures using realistic plasma and EP parameter in a full-f formulation with anisotropic pressure coupling to the bluid background. The code is first benchmarked linearly for the ITPA-TAE as well as the…
In this work, a quasi-linear model for plasma flow response to the resonant magnetic perturbation (RMP) in a tokamak has been rigorously developed in the resistive-inertial (RI) and viscous-resistive (VR) regimes purely from the two-field reduced MHD model. Models for plasma response to RMP are commonly composed of equations for the resonant magnetic field response (i.e. the magnetic island) and the torque balance of plasma flow. However, in previous plasma response models, the magnetic island and the torque balance equations are often derived separately from reduced MHD and full MHD equations…
Axisymmetric ($m=0$) gyrokinetic and extended-MHD simulations of sheared-flow Z-pinch plasma are performed with the high-order finite volume code COGENT. The present gyrokinetic model solves the long-wavelength limit of the gyrokinetic equation for both ion and electron species coupled to the electrostatic gyro-Poisson equation for the electrostatic potential. The electromagnetic MHD model includes the effects of the gyro-viscous pressure tensor, diamagnetic electron and ion heat fluxes, and generalized Ohm's law. A prominent feature of this work is that the radial profiles for the plasma dens…
An analytic scaling relation for the maximum tokamak elongation against n=0 MHD resistive wall modes
为了增加等离子体压力和能量约束以最大化聚变功率输出，高度伸长的等离子体是期望的。然而，存在对最大可实现伸长的限制，其由$n=0$ MHD模式驱动的垂直不稳定性设定。通过优化表征等离子体和壁的几个参数，可以增加该限制。我们研究的目的是探讨如何以及在多大程度上可以做到这一点。具体地说，我们扩展了许多早期的计算的$n=0$模式和数值确定的最大伸长率作为一个功能的无量纲参数描述（1）等离子体轮廓（$β_p$和$l_i$），（2）等离子体形状（$ε$和$δ$），（3）壁半径（$b/a$）和（4）最重要的是反馈系统的能力参数$γτ_w$的缩放关系。这些数值计算依赖于一个新的制定$n=0$磁流体理论，我们最近开发[Freidberg等。等人2015; Lee et. 2015]，将二维稳定性问题简化为一维问题。该方法包括了理想磁流体轴对称不稳定性的所有物理过程，同时显著减少了计算时间，因此在优化过程中可以探索许多参数。也许最有用的最终结果是对模拟的简单解析拟合，其给出最大伸长和相应的优化三角形度作为函数$κ(ε,β_p,l_i,b/a,γτ_w)$和$δ(ε,β_p,l_i,b/a,γτ_w)$。我们提出的比例关系包括最佳的三角形和有限的纵横比上的最大伸长率的影响，并可以用于确定优化的等离子体形状在当前的实验和未来的托卡马克设计。
JOREK 3D non-linear MagnetoHydroDynamic (MHD) simulations of pure Deuterium Shattered Pellet Injection in ITER are presented. It is shown that such a scheme could allow diluting the plasma by more than a factor 10 without immediately triggering large MHD activity, provided the background impurity density is low enough. This appears as a promising strategy to reduce the risk of hot tail Runaway Electron (RE) generation and to avoid RE beams altogether in ITER, motivating further studies in this direction.
