A novel mechanism for the generation and amplification of intrinsic rotation at the low-mode to high-mode transition is presented. The mechanism is one where the net parallel flow is accelerated by turbulence. A preferential direction of acceleration results from the breaking of k ʈ → −k ʈ symmetry by sheared E ϫ B flow. It is shown that the equilibrium pressure gradient contributes a piece of the parallel Reynolds stress, which is nonzero for vanishing parallel flow, and so can accelerate the plasma, driving net intrinsic rotation. Rotation drive, transport, and fluctuation dynamics are treated self-consistently.

Abstract. The theory of turbulent transport of toroidal momentum is discussed in the context of the phenomenon of spontaneous/intrinsic rotation. We review the basic phenomenology and survey the fundamental theoretical concepts. We then proceed to an in-depth discussion of the radial flux of toroidal momentum, with special emphasis on the off-diagonal elements, namely the residual stress (the portion independent of V) and the pinch. A simple model is developed which unifies these effects in a single framework and which recovers many of the features of the Rice scaling trends for intrinsic rotation. We also discuss extensions to finite beta and the effect of SOL boundary conditions. Several issues for future consideration are identified.

This paper presents a novel, unified approach to the theory of turbulent transport of parallel momentum by collisionless drift waves. The physics of resonant and nonresonant off-diagonal contributions to the momentum flux is emphasized, and collisionless momentum exchange between waves and particles is accounted for. Two related momentum conservation theorems are derived. These relate the resonant particle momentum flux, the wave momentum flux, and the refractive force. A perturbative calculation, in the spirit of Chapman–Enskog theory, is used to obtain the wave momentum flux, which contributes significantly to the residual stress. A general equation for mean k∥ (⟨k∥⟩) is derived and used to develop a generalized theory of symmetry breaking. The resonant particle momentum flux is calculated, and pinch and residual stress effects are identified. The implications of the theory for intrinsic rotation and momentum transport bifurcations are discussed.

Residual turbulence from velocity shear stabilized interchange instabilities Phys. Plasmas 20, 012301 (2013); 10.1063/1.4775082 Spatiotemporal temperature fluctuation measurements by means of a fast swept Langmuir probe array Rev. Sci. Instrum. 78, 053505 (2007);We investigate the dynamics of the low(L) ! high(H) transition using a time-dependent, one dimensional (in radius) model which self-consistently describes the time evolution of zonal flows (ZFs), mean flows (MFs), poloidal spin-up, and density and pressure profiles. The model represents the physics of ZF and MF competition, turbulence suppression via E Â B shearing, and poloidal flows driven by turbulence. Numerical solutions of this model show that the L ! H transition can occur via an intermediate phase (I-phase) which involves oscillations of profiles due to ZF and MF competition. The I-phase appears as a nonlinear transition wave originating at the edge boundary and propagates inward. Locally, I-phase exhibits the characteristics of a limit-cycle oscillation. All these observations are consistent with recent experimental results. We examine the trigger of the L ! H transition, by defining a ratio of the rate of energy transfer from the turbulence to the zonal flow to the rate of energy input into the turbulence. When the ratio exceeds order unity, ZF shear gains energy, and a net decay of the turbulence is possible, thus triggering the L ! H transition. Numerical calculations indicate that the L ! H transition is triggered by this peak of the normalized ZF shearing. Zonal flows act as "reservoir," in which to store increasing fluctuation energy without increasing transport, thus allowing the mean flow shear to increase and lock in the transition. A counterpart of the L ! I ! H transition, i.e., an L ! H transition without I-phase, is obtained in a fast power ramp, for which I-phase is compressed into a single burst of ZF, which triggers the transition. Effects of neutral charge exchange on the L ! H transition are studied by varying ZF damping and neoclassical viscosity. Results show that the predicted L ! H transition power increases when either ZF damping or viscosity increase, suggesting a link between recycling, ZF damping, and the L ! H threshold. Studies of fueling effects on the transition and pedestal structure with an emphasis on the particle pinch are reported. V C 2012 American Institute of Physics.