Characteristics of Turbulence-driven Plasma Flow and Origin of Experimental Empirical Scalings of Intrinsic Rotation
Authors: W.X. Wang, T.S. Hahm, S. Ethier, G. Rewoldt, W.M. Tang, W.W. Lee and P.H. Diamond
Abstract: Toroidal plasma flow driven by turbulent torque associated with nonlinear residual stress generation
is shown to recover the observed key features of intrinsic rotation in experiments. Specifically,
the turbulence-driven intrinsic rotation scales close to linearly with plasma gradients and the inverse
of the plasma current, qualitatively reproducing empirical scalings obtained from a large
experimental data base. The effect of magnetic shear on the symmetry breaking in the parallel
wavenumber spectrum is identified. The origin of the current scaling is found to be the enhanced
kll symmetry breaking induced by increased radial variation of the safety factor as the current decreases.
The physics origin for the linear dependence of intrinsic rotation on the pressure gradient
comes from the fact that both turbulence intensity and the zonal flow shear, which are two key
ingredients for driving the residual stress, are increased with the strength of the turbulence drives,
which are R/LTe and R/Lne for the collisionless trapped electron mode (CTEM). Highlighted
results also include robust radial pinches in toroidal flow, heat and particle transport driven by
CTEM turbulence, which emerge "in phase", and are shown to play important roles in determining
plasma profiles. Also discussed are experimental tests proposed to validate findings from these
gyrokinetic simulations.
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Accepted to: Physics of Plasmas (2011)
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Download PPPL-4608 (pdf KB pp)
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