Up-down symmetry of the turbulent transport of toroidal angular momentum   in tokamaks
  Two symmetries of the local nonlinear delta-f gyrokinetic system of equations in tokamaks in the high flow regime are presented. The turbulent transport of toroidal angular momentum changes sign under an up-down reflection of the tokamak and a sign change of both the rotation and the rotation shear. Thus, the turbulent transport of toroidal angular momentum must vanish for up-down symmetric tokamaks in the absence of both rotation and rotation shear. This has important implications for the modeling of spontaneous rotation. 
Felix I. Parra, Michael Barnes and Arthur G. Peeters
physics.plasm-ph