Electromagnetic geodesic acoustic modes in tokamak plasmas

Zhou, Deng

doi:10.1063/1.2793740

Cited by 46 publications

(69 citation statements)

References 23 publications

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“…This system of equations can be used to describe the complete nonlinear dynamics of GAMs using a reduced drift-Braginskii description including the effects of finite β and collisionality. It is evident from the above equations that the GAM does contain m = 1 electromagnetic component which is in contrast to the previous Refs [40,41] …”

Section: Geodesic Acoustic Modecontrasting

confidence: 46%

Geodesic acoustic modes in a fluid model of tokamak plasma: the effects of finite beta and collisionality

Singh

Storelli

Gürcan

et al. 2015

Plasma Phys. Control. Fusion

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Starting from the Braginskii equations, relevant for the tokamak edge region, a complete set of nonlinear equations for the geodesic acoustic modes (GAM) has been derived which includes collisionality, plasma beta and external sources of particle, momentum and heat. Local linear analysis shows that the GAM frequency increases with collisionality at low radial wave number k r and decreases at high k r . GAM frequency also decreases with plasma beta. Radial profiles of GAM frequency for two Tore Supra shots, which were part of a collisionality scan, are compared with these calculations. Discrepency between experiment and theory is observed, which seems to be explained by a finite k r for the GAM when flux surface averaged density n and temperature T are assumed to vanish. It is shown that this agreement is incidental and self-consistent inclusion of n and T responses enhances the disagreement more with k r at high k r . So the discrepancy between the linear GAM calculation, (which persist also for more "complete" linear models such as gyrokinetics) can probably not be resolved by simply adding a finite k

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Section: Geodesic Acoustic Modecontrasting

confidence: 46%

Geodesic acoustic modes in a fluid model of tokamak plasma: the effects of finite beta and collisionality

Singh

Storelli

Gürcan

et al. 2015

Plasma Phys. Control. Fusion

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“…Here, a large aspect-ratio axisymmetric tokamak with straight field line flux coordinates (r, θ, ξ) is considered, with the equilibrium magnetic field given by B 0 = B 0 [e ξ /(1 + cos θ) + ( /q)e θ ], where ξ and θ are, respectively, toroidal and poloidal angle-like flux coordinates of the torus and ≡ r/R 0 is the inverse aspect ratio. We limit our discussion in this paper to the electrostatic case, since the electromagnetic perturbation, with dominant m = 2 poloidal mode structure [2,13] , will not contribute to the GAM dispersion relation. Readers interested in the magnetic perturbations of GAM may refer to Refs.…”

Section: Gam Continuous Spectrum and Mode Conversion To Kgammentioning

confidence: 99%

Kinetic Theories of Geodesic Acoustic Modes: Radial Structure, Linear Excitation by Energetic Particles and Nonlinear Saturation

Qiu

Zonca

Liu

2011

Plasma Sci. Technol.

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Geodesic acoustic modes (GAMs) are oscillating zonal mode structures unique to toroidal plasmas and are capable of regulating microscopic turbulence and associated transports. In this paper, three important aspects of GAM dynamics are investigated, namely (1) GAM continuous spectrum and its mode conversion to kinetic GAM (KGAM); (2) linear excitation of energetic particle induced GAM (EGAM) and its coupling to the GAM continuum, and (3) nonlinear saturation of EGAM via wave particle trapping. The analogy between the GAM-EGAM dynamics and the well known beam-plasma instability are also discussed.

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“…The magnetic perturbations of conventional GAM were theoretically investigated and the poloidal mode number was predicted to be m ¼ 2. 13 However, the magnetic perturbations of EGAM have not been investigated yet. It is worth clarifying the EGAM magnetic perturbations.…”

Section: Introductionmentioning

confidence: 99%

Linear properties of energetic particle driven geodesic acoustic mode

Wang¹,

Todo²

2013

Physics of Plasmas

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Linear properties of energetic particle driven geodesic acoustic mode (EGAM) in the large helical device plasmas are investigated using a hybrid simulation code for a magnetohydrodynamics fluid interacting with energetic particles. It is found that the EGAM is a global mode with the spatially uniform oscillation frequency despite the spatial variation of the local geodesic acoustic mode frequency. The poloidal mode numbers of poloidal velocity fluctuation, plasma density fluctuation, and magnetic fluctuation are m = 0, 1, and 2, respectively. Oscillation frequency, linear growth rate, and spatial width of EGAM are compared for different physics conditions. The EGAM frequency is proportional to the square root of the plasma temperature. The frequency is lower for higher energetic particle β value. The mode spatial width is larger for larger spatial width of the energetic particle distribution and for the reversed shear safety-factor profile than the normal shear profile. It is also found that the EGAM propagates radially outward in the linearly growing phase, and the propagation speed is slower for the spatially broadened modes.

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Electromagnetic geodesic acoustic modes in tokamak plasmas

Cited by 46 publications

References 23 publications

Geodesic acoustic modes in a fluid model of tokamak plasma: the effects of finite beta and collisionality

Geodesic acoustic modes in a fluid model of tokamak plasma: the effects of finite beta and collisionality

Kinetic Theories of Geodesic Acoustic Modes: Radial Structure, Linear Excitation by Energetic Particles and Nonlinear Saturation

Linear properties of energetic particle driven geodesic acoustic mode

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