scholarly journals Low Beta MHD Equilibrium Including a Static Magnetic Island for Reduced MHD Equations in a Straight Heliotron Configuration

2012 ◽  
Vol 7 (0) ◽  
pp. 1403070-1403070
Author(s):  
Kinya SAITO ◽  
Katsuji ICHIGUCHI ◽  
Ryuichi ISHIZAKI
Keyword(s):  
Mhd Equations ◽  
Magnetic Island ◽  
Mhd Equilibrium

Non-standard magnetohydrodynamics equations and their implications in sunspots

2020 ◽  
Vol 476 (2241) ◽  
pp. 20200190
Author(s):  
Rami Ahmad El-Nabulsi
Keyword(s):  
Low Temperature ◽  
Mhd Equations ◽  
Positive Sign ◽  
Magnetic Flux Tube ◽  
Inviscid Fluid ◽  
Interaction Terms ◽  
Conventional Procedure ◽  
Linear Waves ◽  
Mhd Equilibrium ◽  
Alfven Velocity

In this work, we study the physics of plasma waves and magnetohydrodynamic (MHD) equilibrium of sunspots based on the concept of non-standard Lagrangians which play an important role in several branches of science. We derived the modified fluid equations from the Maxwell–Vlasov equation using the moment conventional procedure. Several new interaction terms between physical quantities arise in the non-standard MHD (NS-MHD) equations that give rise to additional features in plasma MHD. A number of fundamental problems in plasma physics are discussed including the non-relativistic dynamics of inviscid fluid subject to the gravitational field, linear waves in plasma MHD and MHD equilibrium of sunspots. For the case of magnetoacoustic wave, it was observed that the NS-MHD equations modify the dispersion relation and its corresponding velocity depends on the sign (positive or negative) of the free parameters introduced in the theory. The non-standard Alfvén velocity is greater than the standard Alfvén velocity for the negative sign and smaller for the positive sign. Besides, in the MHD equilibrium of sunspots, non-standard MHD extends the conventional problem by adding several constraints that lead to an emergence of very low temperature inside the magnetic flux tube comparable to what is observed in low-temperature superconductors. Additional consequences are discussed accordingly.

scholarly journals Investigation of island formation due to RMPs in DIII-D plasmas with the SIESTA resistive MHD equilibrium code

2016 ◽  
Vol 82 (2) ◽  
Author(s):  
S. P. Hirshman ◽  
M. W. Shafer ◽  
S. K. Seal ◽  
J. M. Canik
Keyword(s):  
Field Structure ◽  
Plasma Equilibrium ◽  
Magnetic Island ◽  
Rational Surfaces ◽  
Mhd Equilibrium ◽  
Large Perturbation ◽  
Stable Equilibria ◽  
Numerical Variation ◽  
Stochastic Magnetic Fields ◽  
Parallel Current

The SIESTA magnetohydrodynamic (MHD) equilibrium code has been used to compute a sequence of ideally stable equilibria resulting from numerical variation of the helical resonant magnetic perturbation (RMP) applied to an axisymmetric DIII-D plasma equilibrium. Increasing the perturbation strength at the dominant $m=2$, $n=-1$ resonant surface leads to lower MHD energies and increases in the equilibrium island widths at the $m=2$ (and sidebands) surfaces, in agreement with theoretical expectations. Island overlap at large perturbation strengths leads to stochastic magnetic fields which correlate well with the experimentally inferred field structure. The magnitude and spatial phase (around the dominant rational surfaces) of the resonant (shielding) component of the parallel current are shown to change qualitatively with the magnetic island topology.

scholarly journals Study of Magnetic Island Using a 3D MHD Equilibrium Calculation Code

2011 ◽  
Vol 6 ◽  
pp. 2402134-2402134
Author(s):  
Yasuhiro SUZUKI ◽  
Satoru SAKAKIBARA ◽  
Kiyomasa WATANABE ◽  
Yoshiro NARUSHIMA ◽  
Satoshi OHDACHI ◽  
...  
Keyword(s):  
Magnetic Island ◽  
Equilibrium Calculation ◽  
Mhd Equilibrium ◽  
Calculation Code

scholarly journals Nonlinear Evolution of the Resistive Tearing Mode

1985 ◽  
Vol 107 ◽  
pp. 273-276
Author(s):  
R. S. Steinolfson ◽  
G. van Hoven
Keyword(s):  
Numerical Solutions ◽  
Nonlinear Evolution ◽  
Magnetic Energy ◽  
Nonlinear Behavior ◽  
Mhd Equations ◽  
Tearing Mode ◽  
Magnetic Island ◽  
Long Wavelength ◽  
Nonlinear Growth ◽  
Tearing Instability

Numerical solutions of the MHD equations are used to investigate the nonlinear behavior of the tearing instability. The mode evolves from a linearly growing excitation, followed by a period of greatly reduced nonlinear growth. Constant-Ψ solutions evolve much more slowly than comparable nonconstant-Ψ modes with orders of magnitude less conversion of the stored magnetic energy. The nonconstant-Ψ computations indicate a reduction by approximately 20% of the energy in the initial shear layer. For long–wavelength solutions, secondary–flow vortices, opposite in direction to the linear vortices, generate a new magnetic island centered at the initial x-point.

scholarly journals Effects of plasma turbulence on the nonlinear evolution of magnetic island in tokamak

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Minjun J. Choi ◽  
Lāszlo Bardōczi ◽  
Jae-Min Kwon ◽  
T. S. Hahm ◽  
Hyeon K. Park ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Nonlinear Evolution ◽  
Plasma Turbulence ◽  
Magnetized Plasmas ◽  
Tokamak Plasmas ◽  
Magnetic Islands ◽  
Magnetic Island ◽  
Reconnection Site ◽  
Ambient Turbulence

AbstractMagnetic islands (MIs), resulting from a magnetic field reconnection, are ubiquitous structures in magnetized plasmas. In tokamak plasmas, recent researches suggested that the interaction between an MI and ambient turbulence can be important for the nonlinear MI evolution, but a lack of detailed experimental observations and analyses has prevented further understanding. Here, we provide comprehensive observations such as turbulence spreading into an MI and turbulence enhancement at the reconnection site, elucidating intricate effects of plasma turbulence on the nonlinear MI evolution.

scholarly journals Hamiltonian Approach to Magnetic Fields with Toroidal Surfaces

1985 ◽  
Vol 40 (10) ◽  
pp. 959-967
Author(s):  
A. Salat
Keyword(s):  
Magnetic Field ◽  
Hamiltonian System ◽  
Magnetic Fields ◽  
Constant Pressure ◽  
Time Dependent ◽  
Hamiltonian Approach ◽  
One Dimensional ◽  
Mhd Equilibrium ◽  
Magnetic Surfaces ◽  
Rotational Transform

The equivalence of magnetic field line equations to a one-dimensional time-dependent Hamiltonian system is used to construct magnetic fields with arbitrary toroidal magnetic surfaces I = const. For this purpose Hamiltonians H which together with their invariants satisfy periodicity constraints have to be known. The choice of H fixes the rotational transform η(I). Arbitrary axisymmetric fields, and nonaxisymmetric fields with constant η(I) are considered in detail.Configurations with coinciding magnetic and current density surfaces are obtained. The approach used is not well suited, however, to satisfying the additional MHD equilibrium condition of constant pressure on magnetic surfaces.

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