Excitation of geodesic acoustic mode continuum by drift wave turbulence

Yu, Jun; Dong, J. Q.; Li, X. X.; Du, Dan; Gong, Xianzu

doi:10.1017/s002237781200058x

Cited by 3 publications

(3 citation statements)

References 17 publications

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“…The parametric GAM drive by DWs was generalized to include the radial propagation in a non-uniform plasma and dispersion effects [142,148,225,226]. The analysis in [142,148] has shown that nonlinearly excited GAMs propagate at a group velocity much larger than that predicted by linear theory, and also show the nonlinear shift of the GAM frequency due to the finite amplitude of the DW pump wave.…”

Section: Gam Generation By Reynolds Stressmentioning

confidence: 99%

Geodesic acoustic modes in magnetic confinement devices

Smolyakov

Ido

2021

Nucl. Fusion

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Geodesic acoustic modes (GAMs) are ubiquitous oscillatory flow phenomena observed in toroidal magnetic confinement fusion plasmas, such as tokamaks and stellarators. They are recognized as the non-stationary branch of the turbulence driven zonal flows which play a critical regulatory role in cross-field turbulent transport. GAMs are supported by the plasma compressibility due to magnetic geodesic curvature—an intrinsic feature of any toroidal confinement device. GAMs impact the plasma confinement via velocity shearing of turbulent eddies, modulation of transport, and by providing additional routes for energy dissipation. GAMs can also be driven by energetic particles (so-called EGAMs) or even pumped by a variety of other mechanisms, both internal and external to the plasma, opening-up possibilities for plasma diagnosis and turbulence control. In recent years there have been major advances in all areas of GAM research: measurements, theory, and numerical simulations. This review assesses the status of these developments and the progress made towards a unified understanding of the GAM behaviour and its role in plasma confinement. The review begins with tutorial-like reviews of the basic concepts and theory, followed by a series of topic orientated sections covering different aspects of the GAM. The approach adopted here is to present and contrast experimental observations alongside the predictions from theory and numerical simulations. The review concludes with a comprehensive summary of the field, highlighting outstanding issues and prospects for future developments.

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Section: Gam Generation By Reynolds Stressmentioning

confidence: 99%

Geodesic acoustic modes in magnetic confinement devices

Smolyakov

Ido

2021

Nucl. Fusion

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“…The nonlinear excitation of GAM by DWs can be described by a parametric decay instability [111,112], where pump DW resonantly decay into a GAM and another DW. GAM nonlinear excitation by DW has been investigated by analytical theory [12,46,[113][114][115][116][117][118][119], numerical simulation [120][121][122][123][124][125][126][127]. The underlying three-wave interactions has also been observed experimentally [23,[128][129][130].…”

Section: Nonlinear Gam Excitation By Dwsmentioning

confidence: 99%

Kinetic theory of geodesic acoustic modes in toroidal plasmas: a brief review

Qiu

Chen

Zonca

2018

Plasma Sci. Technol.

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Geodesic acoustic modes (GAM) are oscillating zonal structures unique to toroidal plasmas, and have been extensively studied in the past decades due to their potential capabilities of regulating microscopic turbulences and associated anomalous transport. This article reviews linear and nonlinear theories of GAM; with emphases on kinetic treatment, system nonuniformity and realistic magnetic geometry, in order to reflect the realistic experimental conditions. Specifically, in the linear physics, the resonant wave-particle interactions are discussed, with the application to resonant excitation by energetic particles (EPs). The theory of EP-induced GAM (EGAM) is applied to realistic devices for the interpretation of experimental observations, and global effects due to coupling to GAM continuum are also discussed. Meanwhile, in the nonlinear physics, the spontaneous GAM excitation by microscale turbulences is reviewed, including the effects of various system nonuniformities. A unified theoretical framework of GAM/EGAM is then constructed based on our present understandings. The first-principle-based GAM/EGAM theories reviewed here, thus, provide the tools needed for the understanding and interpretation of experimental/numerical results.

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“…7,9 The excitation of GAM by DW turbulence has been investigated using the paradigm of parametric decay instability in several earlier works. [12][13][14][15][16][17][18][19] However, in these works, the excitation of GAM is investigated either ignoring the plasma nonuniformities or the contribution of kinetic dispersiveness. As we will show in this work, plasma nonuniformities, such as the nonuniformity of diamagnetic frequency x * (r) and/or GAM continuum, 7,20 and the finite linear group velocities of GAM and DW sideband, due to the kinetic dispersiveness, play important roles in the excitation of GAM and qualitatively change the features of parametric decay instability.…”

Section: Introductionmentioning

confidence: 99%