Theory of dissipative density-gradient-driven turbulence in the tokamak edge

Journal Article · Wed May 01 04:00:00 EDT 1985 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.864977· OSTI ID:5882901

Terry, P W; Diamond, P H

A theory of resistive, density-gradient-driven turbulence is presented and compared with tokamak edge fluctuation measurements. In addition to linear driving, the theory accounts for relaxation of the density gradient through a nonlinear process associated with emission from localized density fluctuation elements. From a fluid model for isothermal electrons in toroidal geometry, equations are obtained and solved analytically, retaining both coherent and incoherent contributions. The effect of collisions on the density blobs is treated. A Reynolds number parameterizes the magnitude of the turbulent scattering relative to the collisional viscous diffusion. The analytic results indicate that the spectrum is characterized by linewidths which increase as a function of the Reynolds number and may reach ..delta omega../..omega..> or approx. =1. Energy lies predominantly in the small wavenumbers (k/sub perpendicular/ rho/sub s/approx.0.1). For larger wavenumbers and frequency, the spectrum decays as k/sup -17/6/ and ..omega../sup -2/. The fluctuation level scales as 1/k/sub perpendicular/L/sub n/ and may reach -30% for parameters typical of the pretext edge. Particle diffusion is Bohm-like in magnitude but does not follow Bohm scaling, going instead as n/sup 2//sup ///sup 3/T/sup 1/6//sub e/. The density fluctuations exhibit nonadiabatic character caused by the incoherent mode coupling. An expression for the departure from adiabaticity is given.

• Research Organization: Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712
• DOE Contract Number: FG05-80ET53088
• OSTI ID: 5882901
• Journal Information: Phys. Fluids; (United States), Journal Name: Phys. Fluids; (United States) Vol. 28:5; ISSN PFLDA
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700108* -- Fusion Energy-- Plasma Research-- Wave Phenomena
ANALYTICAL SOLUTION
CLOSED PLASMA DEVICES
COLLISIONAL PLASMA
CORRELATIONS
DIFFUSION
END EFFECTS
EQUATIONS
FLUCTUATIONS
ISOTHERMAL PROCESSES
LINE WIDTHS
NONLINEAR PROBLEMS
PARTICLE LOSSES
PLASMA
PLASMA DENSITY
REYNOLDS NUMBER
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
TURBULENCE
VARIATIONS
VISCOSITY