Dynamic equilibria and magnetohydrodynamic instabilities in toroidal plasmas with non-uniform transport coefficients

Futatani, S.; Moralès, J.; Bos, Wouter J. T.

doi:10.1063/1.4919960

Cited by 3 publications

(3 citation statements)

References 22 publications

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“…Some of this coincidence is fortunate and it would be wise to validate these results using more a more complete MHD description involving the pressure term. However, MHD is already a very simplified description of the actual plasma and ignoring the pressure gradient is only one approximation among many others (for instance, non-uniform resistivity influences the RFP dynamics importantly 29,30 ). It is our viewpoint that MHD simulations should be considered as tools to discover possible physical mechanisms, which can be assessed in realistic experiments.…”

Section: Discussionmentioning

confidence: 99%

On the role and value of β in incompressible MHD simulations

Chahine

Bos

2018

Physics of Plasmas

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The parameter β, defined as the ratio of the pressure to the square of the magnetic field, is widely used to characterize astrophysical and fusion plasmas. However, in the dynamics of a plasma flow it is the pressure gradient which is important rather than the value of the pressure itself. It is shown that if one is interested in the influence of the pressure gradient on the dynamics of a plasma, it is not the quantity β which should be considered, but a similar quantity, depending on the pressure gradient. The scaling of this newly defined quantity is investigated using incompressible magnetohydrodynamic simulations in a periodic cylinder in the Reversed Field Pinch flow regime.

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Section: Discussionmentioning

confidence: 99%

On the role and value of β in incompressible MHD simulations

Chahine

Bos

2018

Physics of Plasmas

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“…2014 a ; Futatani et al. 2015). We have verified by assessing the high-wavenumber range of the kinetic and magnetic energy spectra that the resolution for all simulations was sufficient to resolve all down to the smallest dynamical flow scales.…”

Section: Equations Numerical Methods and Parametersmentioning

confidence: 99%

“…In the present work, we consider a plasma characterized by constant and uniform permeability , permittivity and conductivity . The more complicated case of non-uniform conductivity was considered by Futatani, Morales & Bos (2015). In the MHD description that we consider, the governing equations are the incompressible Navier–Stokes equations including the Lorentz force and the induction equation.…”

Section: Equations Numerical Methods and Parametersmentioning

confidence: 99%

Effect of shaping on turbulent dynamics in reversed-field pinch simulations

2021

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We study the influence of the shape of the plasma container on the dynamics of the reversed-field pinch (RFP). The geometries we consider are periodic cylinders with elliptical and circular-shaped cross-sections. Numerical simulations of fully nonlinear viscoresistive magnetohydrodynamics are carried out to illustrate how the plasma dynamics is affected by shaping. It is shown that independent of the plasma shape, the quantity $\beta$ , comparing the hydrodynamic pressure to the magnetic pressure, decreases for increasing values of the Lundquist number, but the pressure gradient fluctuations remain roughly constant, when compared to the Lorentz force. Different elliptical shapes of the cross-section of the domain lead to the excitation of different toroidal (or axial) magnetic and dynamic modes. Furthermore, it is found that in a geometry with circular cross-section, a significant local poloidal angular momentum is observed, absent in the geometries with elliptical cross-section. Because the confinement is dominantly determined by plasma movement, and the dynamics of the velocity and magnetic field are modified by the modification of the geometry, shaping can thus affect the performance of RFP devices.

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Viscosity impact on 3D non-linear MHD simulations of RFP fusion plasmas

et al. 2023

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Several studies pointed out the joint role of resistivity η and viscosity ν in determining the dynamics and the emergence of helical regimes of reversed-field pinch (RFP) plasmas. In this framework, the self-consistent time evolution of the η and ν coefficients still lacks of a fully satisfying modeling, being constrained by many approximations. In this work, the hypothesis of a flat viscosity profile is relaxed: A viscosity profile inspired by the Braginskii perpendicular viscosity is implemented in the code. This choice is motivated by the fact that the magnetohydrodynamics field instabilities relevant for the RFP configuration dynamics (resistive-kink/tearing modes) are active in the direction perpendicular to the magnetic field. Such a non-monotonous profile causes a localized damping of plasma flow in the regions, where the viscosity is stronger, close to the plasma edge. This results in the reduction of the flow shear, in turn allowing the enhancement of edge magnetic field modes amplitude. The impact on the magnetic topology and on connection length to the wall is also analyzed.

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Dynamic equilibria and magnetohydrodynamic instabilities in toroidal plasmas with non-uniform transport coefficients

Cited by 3 publications

References 22 publications

On the role and value of β in incompressible MHD simulations

On the role and value of β in incompressible MHD simulations

Effect of shaping on turbulent dynamics in reversed-field pinch simulations

Viscosity impact on 3D non-linear MHD simulations of RFP fusion plasmas

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