Transport of Parallel Momentum Induced by Current-Symmetry Breaking in Toroidal Plasmas

Abstract

The symmetry of a physical system strongly impacts on its properties. In toroidal plasmas, the symmetry along a magnetic field line usually constrains the radial flux of parallel momentum to zero in the absence of background flows. By breaking the up-down symmetry of the toroidal currents, this constraint can be relaxed. The parallel asymmetry in the magnetic configuration then leads to an incomplete cancellation of the turbulent momentum flux across a flux surface. The magnitude of the subsequent toroidal rotation increases with the up-down asymmetry and its sign depends on the direction of the toroidal magnetic field and plasma current. Such a mechanism offers new insights in the interpretation and control of the intrinsic toroidal rotation in present day experiments.

Poloidal rotation and its relation to the potential vorticity flux

“…͑18a͒ and ͑18b͒. The perpendicular stress as well as the first contribution to the parallel stress can be recognized as E ϫ B convection of perpendicular 11,31 and parallel momentum, [32][33][34][35] respectively. The second contribution to Eq.…”

A simple model of intrinsic rotation in high confinement regime tokamak plasmas

“…13͒, E ϫ B shear, 7,14 Elsasser population imbalance in Alfvénic turbulence, 15 charge separation induced by polarization drift, 16 up-down asymmetry of flux surfaces, 17 and the turbulence intensity profile itself. Here, since the focus is on H-mode plasmas, we consider E ϫ B shear as the primary symmetry breaking mechanism.…”

Residual parallel Reynolds stress due to turbulence intensity gradient in tokamak plasmas

“…31͒, E ϫ B shear, 29,32 Alfvénic turbulence, 33 charge separation induced by the polarization drift 34 and up-down asymmetry of flux surfaces 35 can be counted among the possible candidates. Parallel flow shear itself, 36 magnetic curvature ͑curvature from B ʈ ‫ء‬ in laboratory frame͒, 26 or the effect of Coriolis drift in rotating frame, 25 can also lead to k ʈ symmetry breaking but give diffusive and pinchlike contributions to the Reynolds stress.…”