The effect of magnetic flutter on residual flow

Terry, P. W.; Pueschel, M. J.; Carmody, D.; Nevins, W. M.

doi:10.1063/1.4828396

Cited by 34 publications

(44 citation statements)

References 18 publications

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“…The resulting radial motion allows them to cross the radial barrier as which the zonal flow acts, thereby contributing to a current that reduces the radial gradient in the electrostatic potential corresponding to the zonal flow. 8 If this diminishing action depletes the zonal flow more quickly than the secondary instability mechanism 7 of the ITG mode is able to replenish it, the system can no longer rely on zonal flow activity to regulate its turbulent dynamics.…”

Section: Introductionmentioning

confidence: 99%

Aspects of the non-zonal transition

2014

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The non-zonal transition, a process which can bring about very large heat fluxes in gyrokinetic simulations, occurs once a certain threshold plasma b is reached. This threshold is parameterized via a simulation database, yielding an expression estimating at what b a given system may approach the transition. Furthermore, the diffusive outward transport of a heat blob in a temperature profile marginally stable with respect to the non-zonal transition is discussed: the resulting transport timescale combines the underlying turbulent transport timescale and the linear instability growth time, thus demonstrating that the non-zonal transition provides a mechanism for very fast heat dissipation. V C 2014 AIP Publishing LLC. [http://dx.

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Section: Introductionmentioning

confidence: 99%

Aspects of the non-zonal transition

2014

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“…To understand the zonal flow dynamics quantitatively, however, both their drive and their depletion mechanisms have to be considered. The latter, in the form of nonlinear mode interaction [27][28][29] or the action of magnetic perturbations on the residual flow [5,30,31], is counteracted by the former: the energy transfer from the linear mode to the zonal mode via sidebands-a process often referred to as secondary instability, as zonal flows saturate the linear mode at the onset of turbulence. The growth rate of the secondary instability gives valuable insights into the zonal flow picture, and its dependence on β is one of the primary subjects of this paper.…”

Section: Introductionmentioning

confidence: 99%

On secondary and tertiary instability in electromagnetic plasma microturbulence

et al. 2013

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Zonal flows, widely accepted to be the secondary instability process leading to the nonlinear saturation of ion temperafture gradient modes, are shown to grow at higher rates relative to the linear mode amplitude as the plasma pressure β is increased-thus confirming that zonal flows become increasingly important in the turbulent dynamics at higher β. At the next level of nonlinear excitation, radial corrugations of the distribution function (zonal flow, zonal density, and zonal temperature) are demonstrated to modify linear growth rates moderately through perturbedfield, self-consistent gradients: on smaller scales, growth rates are reduced below the linear rate.In particular, excitation of kinetic ballooning modes well below their usual threshold is not to be expected under normal conditions. These findings strengthen the theory of the non-zonal transition [M.J. Pueschel et al., Phys. Rev. Lett. 110, 155005 (2013)].

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“…The mechanism behind this phenomenon is the decrease of zonal flow level caused by the magnetic flutter in plasmas with high thermal/magnetic pressure ratio. 4,5 The reduction of turbulence transport levels was also observed in recent stellarator experiments as ZFs presented. 6 Because of the significant role played by ZFs in plasma turbulence evolution, the investigation of their driving, damping, and time evolution is thus of critical importance in determination of turbulence levels for a tokamak discharge.…”

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confidence: 57%

The residual zonal flow in tokamak plasmas toroidally rotating at arbitrary velocity

Zhou

2014

Physics of Plasmas

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Zonal flows, initially driven by ion-temperature-gradient turbulence, may evolve due to the neoclassic polarization in a collisionless tokamak plasma. In our previous work [D. Zhou, Nucl. Fusion 54, 042002 (2014)], the residual zonal flow in a tokamak plasma rotating toroidally at sonic speed is found to have the same form as that of a static plasma. In the present work, the form of the residual zonal flow is presented for tokamak plasmas rotating toroidally at arbitrary velocity. The gyro-kinetic equation is analytically solved for low speed rotation to give the expression of residual zonal flows, and the expression is then generalized for cases with arbitrary rotating velocity through interpolation. The zonal flow level decreases as the rotating velocity increases. The numerical evaluation is in good agreement with the former simulation result for high aspect ratio tokamaks.

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The effect of magnetic flutter on residual flow

Cited by 34 publications

References 18 publications

Aspects of the non-zonal transition

Aspects of the non-zonal transition

On secondary and tertiary instability in electromagnetic plasma microturbulence

The residual zonal flow in tokamak plasmas toroidally rotating at arbitrary velocity

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