Nonlinear Flow Generation By Electrostatic Turbulence In Tokamaks

Technical Report · Wed Jul 07 04:00:00 EDT 2010

DOI:https://doi.org/10.2172/984349· OSTI ID:984349

Wang, W. X.; Diamond, P. H.; Hahm, T. S.; Ethier, S.; Rewoldt, G.; Tang, W. M.

Global gyrokinetic simulations have revealed an important nonlinear flow generation process due to the residual stress produced by electrostatic turbulence of ion temperature gradient (ITG) modes and trapped electron modes (TEM). In collisionless TEM (CTEM) turbulence, nonlinear residual stress generation by both the fluctuation intensity and the intensity gradient in the presence of broken symmetry in the parallel wave number spectrum is identified for the first time. Concerning the origin of the symmetry breaking, turbulence self-generated low frequency zonal flow shear has been identified to be a key, universal mechanism in various turbulence regimes. Simulations reported here also indicate the existence of other mechanisms beyond E × B shear. The ITG turbulence driven “intrinsic” torque associated with residual stress is shown to increase close to linearly with the ion temperature gradient, in qualitative agreement with experimental observations in various devices. In CTEM dominated regimes, a net toroidal rotation is driven in the cocurrent direction by “intrinsic” torque, consistent with the experimental trend of observed intrinsic rotation. The finding of a “flow pinch” in CTEM turbulence may offer an interesting new insight into the underlying dynamics governing the radial penetration of modulated flows in perturbation experiments. Finally, simulations also reveal highly distinct phase space structures between CTEM and ITG turbulence driven momentum, energy and particle fluxes, elucidating the roles of resonant and non-resonant particles.

• Research Organization: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC)
• OSTI ID: 984349
• Report Number(s): PPPL-4532
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ELECTROSTATICS
FLUCTUATIONS
ION TEMPERATURE
ORIGIN
PHASE SPACE
ROTATION
SHEAR
SYMMETRY
SYMMETRY BREAKING
TORQUE
TRAPPED ELECTRONS
TURBULENCE
Tokamaks