Anomalous parallel momentum transport due to E×B flow shear in a tokamak plasma

2009 ◽  
Vol 16 (9) ◽  
pp. 092303 ◽  
Author(s):  
F. J. Casson ◽  
A. G. Peeters ◽  
Y. Camenen ◽  
W. A. Hornsby ◽  
A. P. Snodin ◽  
...  
Keyword(s):  
Momentum Transport ◽  
Tokamak Plasma ◽  
Flow Shear ◽  
Parallel Momentum

Stability of a tokamak plasma with diffuse toroidal rotation

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
O. E. López ◽  
L. Guazzotto
Keyword(s):  
Shooting Method ◽  
Tokamak Plasma ◽  
Solution Technique ◽  
Large Aspect Ratio ◽  
Internal Resonances ◽  
Flow Shear ◽  
Magnetic Shear ◽  
The Stability ◽  
External Kink ◽  
Selection Of

The present work considers the stability of a high- $\beta$ , large aspect ratio, circular plasma with diffuse profiles for the safety factor and the angular toroidal frequency (López & Guazzotto, Phys. Plasmas, vol. 24, 032501). An application of the Frieman–Rotenberg formalism results in a system of scalar eigenmode equations whose coupling is retained at the plasma–vacuum transition but is disregarded across the plasma column, which is a standard practice. The solution technique consists of a multidimensional shooting method for the poloidal harmonics; robust initial guesses are constructed by solving the dispersion relation in the static scenario with vanishing magnetic shear. Flow shear appears as a high- $\beta$ toroidal contribution, and we illustrate its destabilizing influence on $n=1$ external kink modes in the presence of ideal and resistive walls. Internal resonances are avoided by means of the selection of appropriate equilibrium parameters. The stabilizing influence of a finite positive average magnetic shear is also exemplified.

scholarly journals Transition to subcritical turbulence in a tokamak plasma

2016 ◽  
Vol 82 (6) ◽  
Author(s):  
F. van Wyk ◽  
E. G. Highcock ◽  
A. A. Schekochihin ◽  
C. M. Roach ◽  
A. R. Field ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Initial Perturbation ◽  
Outer Core ◽  
Transition To Turbulence ◽  
Tokamak Plasma ◽  
Ion Temperature ◽  
Flow Shear ◽  
Ion Temperature Gradient ◽  
Stability Threshold ◽  
Accretion Flows

Tokamak turbulence, driven by the ion-temperature gradient and occurring in the presence of flow shear, is investigated by means of local, ion-scale, electrostatic gyrokinetic simulations (with both kinetic ions and electrons) of the conditions in the outer core of the Mega-Ampere Spherical Tokamak (MAST). A parameter scan in the local values of the ion-temperature gradient and flow shear is performed. It is demonstrated that the experimentally observed state is near the stability threshold and that this stability threshold is nonlinear: sheared turbulence is subcritical, i.e. the system is formally stable to small perturbations, but, given a large enough initial perturbation, it transitions to a turbulent state. A scenario for such a transition is proposed and supported by numerical results: close to threshold, the nonlinear saturated state and the associated anomalous heat transport are dominated by long-lived coherent structures, which drift across the domain, have finite amplitudes, but are not volume filling; as the system is taken away from the threshold into the more unstable regime, the number of these structures increases until they overlap and a more conventional chaotic state emerges. Whereas this appears to represent a new scenario for transition to turbulence in tokamak plasmas, it is reminiscent of the behaviour of other subcritically turbulent systems, e.g. pipe flows and Keplerian magnetorotational accretion flows.

scholarly journals Symmetry breaking effects of density gradient on parallel momentum transport: A new ρs* effect

2012 ◽  
Vol 19 (1) ◽  
pp. 012301 ◽  
Author(s):  
Rameswar Singh ◽  
R. Singh ◽  
P. Kaw ◽  
Ö. D. Gürcan ◽  
P. H. Diamond ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Density Gradient ◽  
Momentum Transport ◽  
Parallel Momentum ◽  
Effects Of Density

scholarly journals Publisher’s Note: “Symmetry breaking effects of density gradient on parallel momentum transport: A new ρs* effect” [Phys. Plasmas 19, 012301 (2012)]

2012 ◽  
Vol 19 (3) ◽  
pp. 039901
Author(s):  
Rameswar Singh ◽  
R. Singh ◽  
P. Kaw ◽  
Ö. D. Gürcan ◽  
P. H. Diamond ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Density Gradient ◽  
Momentum Transport ◽  
Parallel Momentum ◽  
Effects Of Density

scholarly journals Flow shear induced fluctuation suppression in finite aspect ratio shaped tokamak plasma

1995 ◽  
Vol 2 (5) ◽  
pp. 1648-1651 ◽  
Author(s):  
T. S. Hahm ◽  
K. H. Burrell
Keyword(s):  
Aspect Ratio ◽  
Tokamak Plasma ◽  
Flow Shear

Nonlinear turbulent parallel momentum transport due to blobs

2019 ◽  
Vol 59 (7) ◽  
pp. 076011
Author(s):  
Yang Li ◽  
Jiquan Li ◽  
Zhe Gao
Keyword(s):  
Momentum Transport ◽  
Parallel Momentum

scholarly journals Ion heat and parallel momentum transport by stochastic magnetic fields and turbulence

2021 ◽  
Author(s):  
Chang-Chun Chen ◽  
Patrick Diamond ◽  
Steve Tobias
Keyword(s):  
Residual Stress ◽  
Magnetic Fields ◽  
Critical Parameter ◽  
Turbulent Transport ◽  
Momentum Transport ◽  
Viscous Stress ◽  
Scattering Rate ◽  
Stochastic Magnetic Fields ◽  
Parallel Momentum ◽  
Acoustic Dispersion

Abstract The theory of turbulent transport of parallel momentum and ion heat by the interaction of stochastic magnetic fields and turbulence is presented. Attention is focused on determining the kinetic stress and the compressive energy flux. A critical parameter is identified as the ratio of the turbulent scattering rate to the rate of parallel acoustic dispersion. For the parameter large, the kinetic stress takes the form of a viscous stress. For the parameter small, the quasilinear residual stress is recovered. In practice, the viscous stress is the relevant form, and the quasilinear limit is not observable. This is the principal prediction of this paper. A simple physical picture is developed and shown to recover the results of the detailed analysis.

Sign in / Sign up

Export Citation Format

Share Document