Stabilization of sawteeth in tokamaks with toroidal flows

Sheared toroidal flows with a magnitude of the order of the sound speed are shown to stabilize sawteeth in tokamaks. In the absence of flows, tokamak equilibria in which the central safety factor q is less than unity are unstable to resistive tearing modes ~resistive internal kink modes! with toroidal mode number n51. As the ratio b of the plasma pressure to the magnetic field pressure increases, the growth rate of the n51 mode rises because of the increasing pressure gradient. However, the addition of a toroidal flow to the equilibrium has a stabilizing effect. As the magnitude of the toroidal flow approaches the sound speed, the n51 resistive tearing mode can be completely stabilized by the flow, eliminating sawteeth. © 2002 American Institute of Physics. @DOI: 10.1063/1.1485974#