Theory of neoclassical ion temperature-gradient-driven turbulence

Journal Article · Fri Feb 01 04:00:00 EST 1991 · Physics of Fluids B; (USA)

DOI:https://doi.org/10.1063/1.859748· OSTI ID:6251886

Kim, Y B; Diamond, P H; Biglari, H ^[1]; Callen, J D ^[2]

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1. Department of Physics, University of California, San Diego, La Jolla, CA (USA)
2. Departments of Nuclear Engineering and Physics, University of Wisconsin, Madison, Wisconsin (USA)

The theory of collisionless fluid ion temperature-gradient-driven turbulence is extended to the collisional banana-plateau regime. Neoclassical ion fluid evolution equations are developed and utilized to investigate linear and nonlinear dynamics of negative compressibility {eta}{sub {ital i}} modes ({eta}{sub {ital i}}{equivalent to}{ital d} ln {ital T}{sub {ital i}}/{ital d} ln {ital n}{sub {ital i}}). In the low-frequency limit ({omega}{lt}{mu}{sub {ital i}}, where {omega} is the mode frequency and {mu}{sub {ital i}} is the neoclassical viscous damping frequency), neoclassical effects modify the sonic {eta}{sub {ital i}} mode by introducing strong viscous damping of parallel flows, which renders the long wavelength response dissipative rather than inertial. Also, the linear and nonlinear polarization drifts are enhanced by a factor of {ital B}{sup 2}{sub {ital t}}/{ital B}{sup 2}{sub {ital p}}. As a result of these modifications, growth rates are dissipative, rather than sonic, and radial mode widths are broadened (i.e., {gamma}{similar to}{ital k}{sup 2}{sub {parallel}}{ital c}{sup 2}{sub {ital s}}({eta}{sub {ital i}} {minus}(2)/(3) )/{mu}{sub {ital i}}, {Delta}{sub {ital x}}{similar to}{rho}{sub {ital s}}({ital B}{sub {ital t}}/{ital B}{sub {ital p}}) (1+{eta}{sub {ital i}}){sup 1/2}, where {ital k}{sub {parallel}}, {ital c}{sub {ital s}}, and {rho}{sub {ital s}} are the parallel wave number, sound velocity, and ion gyroradius, respectively). In the limit of weak viscous damping, enhanced neoclassical polarization persists and broadens radial mode widths. Linear mixing length estimates and renormalized turbulence theory are used to determine the ion thermal diffusivity in both cases. In both cases, a strong favorable dependence of ion thermal diffusivity on {ital B}{sub {ital p}} (and hence plasma current) is exhibited.

• OSTI ID: 6251886
• Journal Information: Physics of Fluids B; (USA), Journal Name: Physics of Fluids B; (USA) Journal Issue: 2 Vol. 3:2; ISSN 0899-8221; ISSN PFBPE
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700108* -- Fusion Energy-- Plasma Research-- Wave Phenomena
BANANA REGIME
COLLISIONAL PLASMA
EQUATIONS
ION TEMPERATURE
PLASMA
PLATEAU REGIME
TEMPERATURE GRADIENTS
TRAPPING
TURBULENCE