Excitation of Zonal Flow by Drift Waves in Toroidal Plasmas

Chen, L.; White, R.B.; Lin, Z.

doi:10.2172/14454

Cited by 19 publications

(38 citation statements)

References 5 publications

(6 reference statements)

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“…Such flows are thought to be implicated in the formation and evolution of transport barriers in tokamaks and stellarators. 2,4 On the theoretical side, a number of researchers [5][6][7][8][9][10] have examined the possibility of suppressing turbulence by radial decorrelation due to strongly sheared EÃB flow shear and have contributed a variety of models which exhibit this effect ͑some of this work is reviewed in Refs. 4 -11͒.…”

Section: Introductionmentioning

confidence: 99%

The nonlinear dynamics of the modulational instability of drift waves and the associated zonal flows

2001

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The linear and nonlinear dynamics of zonal flows and their interactions with drift wave turbulence is considered in the simple but illuminating generalized Charney–Hasegawa–Mima model due to Smolyakov et al. [Phys. Plasmas 7, 1349 (2000)]. Two positive definite, exact, integral invariants associated with the full generalized Charney–Hasegawa–Mima system are derived. For an initial monochromatic drift wave pump with small but finite amplitude, a modulational instability can occur, characterized by growing zonal flow and sideband perturbations (i.e., a four-wave interaction). The pump threshold for instability is readily satisfied, depending on the zonal flow wave number. The fully nonlinear Charney–Hasegawa–Mima equations are solved with a numerical scheme which is validated by demonstrating the conservation of the two exact invariants. The simulations show that the validity of the four-wave model is limited to approximately three instability growth times. The radial structure of the zonal flow can be “jet-like” or highly oscillatory depending upon the ratio of the system size to the density scale length and initial conditions. It is found that zonal flows can be dramatically reduced if the most unstable zonal flow wave number does not fit into the system.

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Section: Introductionmentioning

confidence: 99%

The nonlinear dynamics of the modulational instability of drift waves and the associated zonal flows

2001

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“…The first one uses the classical coherent parametric instability approach to study the mechanism associated with the generation of shear flow. [13][14][15][16][17][18][19][20] In the second approach, 21-26 the drift waves are represented by a wavekinetic equation coupled to the zonal flow equation. In the wave-kinetic analysis there is an intrinsic separation in the scale-lengths between the ''short'' scale drift wave and the long scale zonal flows.…”

Section: Introductionmentioning

confidence: 99%

Zonal flow and field generation by finite beta drift waves and kinetic drift-Alfvén waves

et al. 2001

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A study of the generation of zonal flows and zonal magnetic fields by finite beta drift waves and kinetic drift-Alfvén waves is presented. The analysis is a generalization of recent investigations of the modulational instability for zonal flow generation by electrostatic drift waves to finite beta drift waves and kinetic drift-Alfvén waves. The drift wave driven unstable zonal flows/fields are stabilized by finite β below a critical value, due to the finite beta modification of the drift wave pump and the drift sidebands. They are, however, destabilized by coupling to the zonal field for larger β. The drift-Alfvén branch driven zonal flows/fields are found to be completely stable below a critical β, and are destabilized for larger β. These new results can find applications in a variety of laboratory and space plasma situations.

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“…Avenues being explored include the role of collisional Alfven waves, induced by the beam ions which then stochastically heat the thermal ions through nonlinear wave-particle interactions [9]. The work is an extension of nonlinear theory developed to explain the anomalously high ion temperatures measured in solar coronal loops [10]. Also, the role of small aspect ratio effects on collisional coupling are being…”

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confidence: 99%

Initial studies of core and edge transport of NSTX plasmas

Synakowski

Bell

et al. 2002

Plasma Phys. Control. Fusion

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-Rapidly developing diagnostic, operational, and analysis capability is enabling the first detailed local physics studies to begin in high beta plasmas of the National Spherical Torus Experiment (NSTX).These studies are motivated in part by energy confinement times in neutral-beam-heated discharges that are favorable with respect to predictions from the ITER-89P scaling expression. Analysis of heat fluxes based on profile measurements with NBI suggest that the ion thermal transport may be exceptionally low, and that electron thermal transport is the dominant loss channel. This analysis motivates studies of possible sources of ion heating not presently accounted for by classical collisional processes. Gyrokinetic microstability studies indicate that long wavelength turbulence with k θ ρ i ~ 0.1 -1 may be suppressed in these plasmas, while modes with k θ ρ I ~ 50 may be robust. High harmonic fast wave (HHFW) heating efficiently heats electrons on NSTX, and studies have begun using it to to assess transport in the electron channel. Regarding edge transport, H-mode transitions occur with either NBI or HHFW heating. The power required for L-to H-mode transitions far exceeds that expected from empirical ELM-free H mode scaling laws derived from moderate aspect ratio devices. Finally, initial fluctuation measurements made with two techniques are permitting the first characterizations of edge turbulence.

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Excitation of Zonal Flow by Drift Waves in Toroidal Plasmas

Cited by 19 publications

References 5 publications

The nonlinear dynamics of the modulational instability of drift waves and the associated zonal flows

The nonlinear dynamics of the modulational instability of drift waves and the associated zonal flows

Zonal flow and field generation by finite beta drift waves and kinetic drift-Alfvén waves

Initial studies of core and edge transport of NSTX plasmas

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