Theory of weak ion temperature gradient-driven turbulence near the threshold of instability

Journal Article · Sun Oct 01 00:00:00 EDT 1989 · Physics of Fluids B: Plasma Physics; (USA)

DOI:https://doi.org/10.1063/1.859061· OSTI ID:5588774

Mattor, N ^[1]; Diamond, P H ^[2]

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1. Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (US)
2. Department of Physics, University of California, San Diego, La Jolla, California 92093 and General Atomics, San Diego, California 92138

In this paper a theory of weak ion temperature gradient-driven turbulence near the threshold of instability is presented. The model considers kinetic ions and adiabatic electrons in a sheared slab geometry. Linear theory shows that for {eta}{sub th}{lt}{eta}{sub {ital i}}{approx lt}{eta}{sub th}+(1+{ital T}{sub {ital i}}/{ital T}{sub {ital e}}) {ital L}{sub {ital n}}/{ital L}{sub {ital s}} (where {eta}{sub th}=0.95 is the instability threshold and {ital L}{sub {ital n}}/{ital L}{sub {ital s}}{much lt}1) then {gamma}{much lt}{omega} and a weak turbulence theory applies. The nonlinear wave kinetic equation indicates that ion Compton scattering is the dominant nonlinear saturation process, and it is shown that the energy scatters to the linearly stable low {ital k}{sub {ital y}} modes. The resulting fluctuation spectrum (peaked about {ital k}{sub {perpendicular}}{rho}{sub {ital i}}{congruent}1) is much lower than that suggested by naive extrapolation from the strong turbulence regime. The resulting ion thermal conductivity is also extremely low, so that strong ion heating can be expected to drive the ion temperature gradient to a level where this weakly turbulent threshold regime is surpassed. Thus the critical {eta}{sub {ital i}} relevant to magnetic confinement experiments is not the linear instability threshold but the point where the diminutions of the weak turbulence regime vanish, and the transport increases to the strong fluid turbulence level.

• OSTI ID: 5588774
• Journal Information: Physics of Fluids B: Plasma Physics; (USA), Vol. 1:10; ISSN 0899-8221
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
PLASMA
TURBULENCE
ADIABATIC PROCESSES
COMPTON EFFECT
ELECTRONS
IONS
KINETICS
NONLINEAR PROBLEMS
PLASMA INSTABILITY
SHEAR
SLABS
TEMPERATURE GRADIENTS
THERMAL CONDUCTIVITY
THRESHOLD ENERGY
BASIC INTERACTIONS
CHARGED PARTICLES
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
ENERGY
FERMIONS
INSTABILITY
INTERACTIONS
LEPTONS
PHYSICAL PROPERTIES
SCATTERING
THERMODYNAMIC PROPERTIES
700107* - Fusion Energy- Plasma Research- Instabilities