Heuristic theory of nonlocally broken gyro-Bohm scaling

Journal Article · Fri Jul 15 04:00:00 EDT 2005 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.1947467· OSTI ID:20764379

Waltz, R E; Candy, J ^[1]

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1. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

Global gyrokinetic simulations of ion temperature gradient turbulent transport with piecewise-flat profiles are given to illustrate the breaking of gyro-Bohm scaling by a nonlocal mechanism. The nonlocal drainage of the turbulence from unstable regions spreading into stable (or less unstable) regions breaks the gyro-Bohm scaling toward Bohm in unstable regions and toward super-gyro-Bohm in stable (or less unstable) regions. A heuristic model for this nonlocal process is formulated in terms of a nonlocal growth rate resulting from a locally weighted radial average of the local linear ballooning mode growth rate. A nonlocality length L measured in ion gyroradii provides the exponential scale for the local weighting. The nonlocal growth rate can be incorporated into a local gyro-Bohm-scaled transport model in place of the local growth rate. The resulting nonlocal transport model will provide some transport in stable regions. A heuristic theory of this nonlocal transport mechanism based on the partial formation of global modes in toroidal geometry is detailed. The theory argues that the nonlocality length L increases with relative gyroradius and decreases with the linear growth rate.

• OSTI ID: 20764379
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 7 Vol. 12; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BALLOONING INSTABILITY
CHARGED-PARTICLE TRANSPORT
ELECTRON TEMPERATURE
GEOMETRY
ION TEMPERATURE
PLASMA
PLASMA SIMULATION
SCALING LAWS
TEMPERATURE GRADIENTS
TRANSPORT THEORY
TURBULENCE