2020
2.
Pfefferlé, David; Noakes, Lyle; Zhou, Yao
Rigidity of MHD equilibria to smooth incompressible ideal motion near resonant surfaces Journal Article
In: Plasma Physics and Controlled Fusion, vol. 62, no. 7, pp. 074004, 2020.
Abstract | Links | BibTeX | Tags: Hamiltonian, MHD, MHD equilibrium, perturbation theory, resonant surfaces
@article{pfefferle-rigidityb,
title = {Rigidity of MHD equilibria to smooth incompressible ideal motion near resonant surfaces},
author = {David Pfefferl\'{e} and Lyle Noakes and Yao Zhou},
url = {https://doi.org/10.1088%2F1361-6587%2Fab8ca3},
doi = {10.1088/1361-6587/ab8ca3},
year = {2020},
date = {2020-06-01},
journal = {Plasma Physics and Controlled Fusion},
volume = {62},
number = {7},
pages = {074004},
publisher = {IOP Publishing},
abstract = {In ideal MHD, the magnetic flux is advected by the plasma motion, freezing flux-surfaces into the flow. An MHD equilibrium is reached when the flow relaxes and force balance is achieved. We ask what classes of MHD equilibria can be accessed from a given initial state via smooth incompressible ideal motion. It is found that certain boundary displacements are formally not supported. This follows from yet another investigation of the Hahm\textendashKulsrud\textendashTaylor (HKT) problem, which highlights the resonant behaviour near a rational layer formed by a set of degenerate critical points in the flux-function. When trying to retain the mirror symmetry of the flux-function with respect to the resonant layer, the vector field that generates the volume-preserving diffeomorphism vanishes at the identity to all order in the time-like path parameter.},
keywords = {Hamiltonian, MHD, MHD equilibrium, perturbation theory, resonant surfaces},
pubstate = {published},
tppubtype = {article}
}
In ideal MHD, the magnetic flux is advected by the plasma motion, freezing flux-surfaces into the flow. An MHD equilibrium is reached when the flow relaxes and force balance is achieved. We ask what classes of MHD equilibria can be accessed from a given initial state via smooth incompressible ideal motion. It is found that certain boundary displacements are formally not supported. This follows from yet another investigation of the Hahm–Kulsrud–Taylor (HKT) problem, which highlights the resonant behaviour near a rational layer formed by a set of degenerate critical points in the flux-function. When trying to retain the mirror symmetry of the flux-function with respect to the resonant layer, the vector field that generates the volume-preserving diffeomorphism vanishes at the identity to all order in the time-like path parameter.
2019
1.
Lanthaler, S; Graves, J P; Pfefferlé, D; Cooper, W A
Guiding-centre theory for kinetic-magnetohydrodynamic modes in strongly flowing plasmas Journal Article
In: Plasma Physics and Controlled Fusion, vol. 61, no. 7, pp. 074006, 2019.
Abstract | Links | BibTeX | Tags: drift-kinetic, guiding-centre, MHD, plasma flow
@article{lanthaler-2019,
title = {Guiding-centre theory for kinetic-magnetohydrodynamic modes in strongly flowing plasmas},
author = {S Lanthaler and J P Graves and D Pfefferl\'{e} and W A Cooper},
url = {https://doi.org/10.1088%2F1361-6587%2Fab1d21},
doi = {10.1088/1361-6587/ab1d21},
year = {2019},
date = {2019-05-01},
journal = {Plasma Physics and Controlled Fusion},
volume = {61},
number = {7},
pages = {074006},
publisher = {IOP Publishing},
abstract = {A kinetic-magnetohydrodynamic model with kinetic pressure closure is derived from a consistent guiding-centre framework. Higher-order (gyroviscous) corrections to the pressure tensor are derived in complex geometry from a reduced kinetic equation. The proposed model allows for flows of the order of the thermal ion velocity, taking into account important centrifugal effects due to the ExB flow, as well as the effects of diamagnetic flows associated with finite Larmor radius corrections to both ion fluid inertia and long mean-free path contributions. Wave\textendashparticle interactions, such as toroidal drift-resonance, are retained. Furthermore, the linearised model includes a quasi-neutrality equation, allowing the effects of a parallel electric field to be studied in fast rotating tokamak plasmas.},
keywords = {drift-kinetic, guiding-centre, MHD, plasma flow},
pubstate = {published},
tppubtype = {article}
}
A kinetic-magnetohydrodynamic model with kinetic pressure closure is derived from a consistent guiding-centre framework. Higher-order (gyroviscous) corrections to the pressure tensor are derived in complex geometry from a reduced kinetic equation. The proposed model allows for flows of the order of the thermal ion velocity, taking into account important centrifugal effects due to the ExB flow, as well as the effects of diamagnetic flows associated with finite Larmor radius corrections to both ion fluid inertia and long mean-free path contributions. Wave–particle interactions, such as toroidal drift-resonance, are retained. Furthermore, the linearised model includes a quasi-neutrality equation, allowing the effects of a parallel electric field to be studied in fast rotating tokamak plasmas.