Excitation of zonal flow by nonlinear geodesic acoustic mode

2020 ◽  
Vol 27 (3) ◽  
pp. 034501
Author(s):  
Haijun Ren ◽  
X. Q. Xu
Keyword(s):  
Zonal Flow ◽  
Acoustic Mode ◽  
Geodesic Acoustic Mode

Toroidal Symmetry of the Geodesic Acoustic Mode Zonal Flow in a Tokamak Plasma

2006 ◽  
Vol 96 (25) ◽  
Author(s):  
K. J. Zhao ◽  
T. Lan ◽  
J. Q. Dong ◽  
L. W. Yan ◽  
W. Y. Hong ◽  
...  
Keyword(s):  
Zonal Flow ◽  
Acoustic Mode ◽  
Tokamak Plasma ◽  
Geodesic Acoustic Mode

scholarly journals Trapped particle precession and sub-bounce zonal flow dynamics in tokamaks

2018 ◽  
Vol 84 (1) ◽  
Author(s):  
W. Sengupta ◽  
A. B. Hassam
Keyword(s):  
Angular Momentum ◽  
Electric Field ◽  
Radial Electric Field ◽  
Zonal Flow ◽  
Acoustic Mode ◽  
Apparent Paradox ◽  
Zonal Flows ◽  
Long Wavelength ◽  
Particle Flows ◽  
Geodesic Acoustic Mode

A drift-kinetic calculation in an axisymmetric tokamak, with super-diamagnetic flows, is presented to elucidate the relation between the radial electric field, $E_{r}$, zonal flows and the rapid precession of the trapped particle (TP) population. It has been shown earlier (Rosenbluth & Hinton, Phys. Rev. Lett., vol. 80(4), 1998, p. 724, hereafter RH) that an initial radial electric field results in geodesic acoustic mode oscillations which subsequently Landau damp, resulting in a much smaller final residual electric field, and accompanying parallel zonal flows. We observe an apparent paradox: the final angular momentum in the RH parallel zonal flow is much smaller than the angular momentum expected from the well-known rapid precession of the trapped particle population in the RH residual electric field. We reconcile this paradox by illuminating the presence of a population of reverse circulating particle flows that, dominantly, are equal and opposite to the rapid TP precession. Mathematically, the calculation is facilitated by transforming to an energy coordinate shifted from conventional by an amount proportional to $E_{r}$. We also discuss the well-known RH coefficient in the context of effective mass and show how the TP precession and the opposite circulating flows contribute to this mass. Finally, we show that in the long wavelength limit, the RH flows and RH coefficient arise as a natural consequence of conservation of toroidal angular momentum and the second adiabatic invariant.

The intermittent excitation of geodesic acoustic mode by resonant Instanton of electron drift wave envelope in L-mode discharge near tokamak edge

2021 ◽  
Author(s):  
Liu Zhao-Yang ◽  
Zhang Yang-Zhong ◽  
Swadesh Mitter Mahajan ◽  
Liu A-Di ◽  
Zhou Chu ◽  
...  
Keyword(s):  
Group Velocity ◽  
Reynolds Stress ◽  
Traveling Wave ◽  
Zonal Flow ◽  
Acoustic Mode ◽  
Flow Equation ◽  
Electron Drift ◽  
Drift Wave ◽  
Wave Phase ◽  
Geodesic Acoustic Mode

Abstract There are two distinct phases in the evolution of drift wave envelope in the presence of zonal flow. A long-lived standing wave phase, which we call the Caviton, and a short-lived traveling wave phase (in radial direction) we call the Instanton. Several abrupt phenomena observed in tokamaks, such as intermittent excitation of geodesic acoustic mode (GAM) shown in this paper, could be attributed to the sudden and fast radial motion of Instanton. The composite drift wave – zonal flow system evolves at the two well-separate scales: the micro and the meso-scale. The eigenmode equation of the model defines the zero order (micro-scale) variation; it is solved by making use of the two dimensional (2D) weakly asymmetric ballooning theory (WABT), a theory suitable for modes localized to rational surface like drift waves, and then refined by shifted inverse power method, an iterative finite difference method. The next order is the equation of electron drift wave (EDW) envelope (containing group velocity of EDW) which is modulated by the zonal flow generated by Reynolds stress of EDW. This equation is coupled to the zonal flow equation, and numerically solved in spatiotemporal representation; the results are displayed in self-explanatory graphs. One observes a strong correlation between the Caviton-Instanton transition and the zero-crossing of radial group velocity of EDW. The calculation brings out the defining characteristics of the Instanton: it begins as a linear traveling wave right after the transition. Then, it evolves to a nonlinear stage with increasing frequency all the way to 20 kHz. The modulation to Reynolds stress in zonal flow equation brought in by the nonlinear Instanton will cause resonant excitation to GAM. The intermittency is shown due to the random phase mixing between multiple central rational surfaces in the reaction region.

Characteristics of geodesic acoustic mode zonal flow and ambient turbulence at the edge of the HL-2A tokamak plasmas

2007 ◽  
Vol 14 (12) ◽  
pp. 122301 ◽  
Author(s):  
K. J. Zhao ◽  
J. Q. Dong ◽  
L. W. Yan ◽  
W. Y. Hong ◽  
T. Lan ◽  
...  
Keyword(s):  
Zonal Flow ◽  
Acoustic Mode ◽  
Tokamak Plasmas ◽  
Geodesic Acoustic Mode ◽  
Ambient Turbulence

Effects of passing energetic particles on geodesic acoustic mode

2014 ◽  
Vol 21 (10) ◽  
pp. 102506 ◽  
Author(s):  
Haijun Ren ◽  
Chao Dong
Keyword(s):  
Energetic Particles ◽  
Acoustic Mode ◽  
Geodesic Acoustic Mode

Geodesic Acoustic Mode in Toroidal Plasma

2010 ◽  
Author(s):  
N. Chakrabarti ◽  
P. N. Guzdar ◽  
R. G. Kleva ◽  
R. Singh ◽  
P. K. Kaw ◽  
...  
Keyword(s):  
Acoustic Mode ◽  
Toroidal Plasma ◽  
Geodesic Acoustic Mode

Nonlinear excitation of a geodesic acoustic mode by reversed shear Alfvén eignemodes

2021 ◽  
Author(s):  
Yahui Wang ◽  
Tao Wang ◽  
Shizhao Wei ◽  
Zhiyong Qiu
Keyword(s):  
Steady State ◽  
Plasma Heating ◽  
Acoustic Mode ◽  
Decay Process ◽  
Nonlinear Excitation ◽  
Parametric Decay ◽  
Geodesic Acoustic Mode ◽  
Burning Plasmas ◽  
Reversed Shear ◽  
Excitation Conditions

Abstract The parametric decay process of a reversed shear Alfv\'{e}n eigenmeode (RSAE) into a geodesic acoustic mode (GAM) and a kinetic reversed shear Alfv\'{e}n eigenmode (KRSAE) is investigated using nonlinear gyrokinetic theory. The excitation conditions mainly require the pump RSAE amplitude to exceed a certain threshold, which could be readily satisfied in burning plasmas operated in steady-state advanced scenario. This decay process can contribute to thermal plasma heating and confinement improvement.

Electromagnetic characteristics of geodesic acoustic mode in the COMPASS tokamak

2017 ◽  
Vol 57 (12) ◽  
pp. 126048 ◽  
Author(s):  
J. Seidl ◽  
J. Krbec ◽  
M. Hron ◽  
J. Adamek ◽  
C. Hidalgo ◽  
...  
Keyword(s):  
Acoustic Mode ◽  
Geodesic Acoustic Mode ◽  
Electromagnetic Characteristics

scholarly journals Comprehensive comparisons of geodesic acoustic mode characteristics and dynamics between Tore Supra experiments and gyrokinetic simulations

2015 ◽  
Vol 22 (6) ◽  
pp. 062508 ◽  
Author(s):  
A. Storelli ◽  
L. Vermare ◽  
P. Hennequin ◽  
Ö. D. Gürcan ◽  
G. Dif-Pradalier ◽  
...  
Keyword(s):  
Acoustic Mode ◽  
Geodesic Acoustic Mode ◽  
Mode Characteristics ◽  
Gyrokinetic Simulations
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