Nonlinear gyrokinetic theory of toroidal momentum pinch

Journal Article · Sun Jul 15 00:00:00 EDT 2007 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2743642· OSTI ID:20975149

Hahm, T S; Diamond, P H; Gurcan, O D; Rewoldt, G ^[1]

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1. Princeton University, Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States)

The turbulent convective flux of the toroidal angular momentum density is derived using the nonlinear toroidal gyrokinetic equation which conserves phase space density and energy [T. S. Hahm, Phys. Fluids, 31, 2670 (1988)]. A novel pinch mechanism is identified which originates from the symmetry breaking due to the magnetic field curvature. A net parallel momentum transfer from the waves to the ion guiding centers is possible when the fluctuation intensity varies on the flux surface, resulting in imperfect cancellation of the curvature drift contribution to the parallel acceleration. This mechanism is inherently a toroidal effect, and complements the k{sub parallel} symmetry breaking mechanism due to the mean ExB shear [O. Gurcan et al., Phys. Plasmas 14, 042306 (2007)] which exists in a simpler geometry. In the absence of ion thermal effects, this pinch velocity of the angular momentum density can also be understood as a manifestation of a tendency to homogenize the profile of ''magnetically weighted angular momentum density,'' nm{sub i}R{sup 2}{omega}{sub parallel}/B{sup 2}. This part of the pinch flux is mode-independent (whether it is trapped electron mode or ion temperature gradient mode driven), and radially inward for fluctuations peaked at the low-B-field side, with a pinch velocity typically, V{sub Ang}{sup TEP}{approx}-2{chi}{sub {phi}}/R{sub 0}. Ion thermal effects introduce an additional radial pinch flux from the coupling with the curvature and grad-B drifts. This curvature driven thermal pinch can be inward or outward, depending on the mode-propagation direction. Explicit formulas in general toroidal geometry are presented.

• OSTI ID: 20975149
• Journal Information: Physics of Plasmas, Vol. 14, Issue 7; Other Information: DOI: 10.1063/1.2743642; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANGULAR MOMENTUM
FLUCTUATIONS
GEOMETRY
ION TEMPERATURE
IONS
MAGNETIC FIELDS
MAGNETIC SURFACES
MOMENTUM TRANSFER
NONLINEAR PROBLEMS
PHASE SPACE
PINCH EFFECT
PLASMA
PLASMA DENSITY
PLASMA INSTABILITY
SYMMETRY BREAKING
TEMPERATURE DEPENDENCE
TEMPERATURE GRADIENTS
TOKAMAK DEVICES
TRAPPED ELECTRONS