title: Momentum injection in tokamak plasmas and transitions to reduced transport.
abstract: The effect of momentum injection on the temperature gradient in tokamak plasmas is studied. A plausible scenario for transitions to reduced transport regimes is proposed. The transition happens when there is sufficient momentum input so that the velocity shear can suppress or reduce the turbulence. However, it is possible to drive too much velocity shear and rekindle the turbulent transport. The optimal level of momentum injection is determined. The reduction in transport is maximized in the regions of low or zero magnetic shear.
authors.affiliation: Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP, United Kingdom. f.parradiaz1@physics.ox.ac.uk
authors.forename: F I
authors.initials: FI
authors.lastname: Parra
authors.forename: M
authors.initials: M
authors.lastname: Barnes
authors.forename: E G
authors.initials: EG
authors.lastname: Highcock
authors.forename: A A
authors.initials: AA
authors.lastname: Schekochihin
authors.forename: S C
authors.initials: SC
authors.lastname: Cowley