Time-dependent plasma viscosity and poloidal flow damping with orbit squeezing in tokamaks

In the vicinity of a magnetic island and in the zonal flow, the radial extent of the radial electric field layer is about the width of the ion poloidal gyroradius in tokamaks. Thus, the effects of the orbit squeezing become important in these situations and probably in other applications as well. It is shown that the poloidal flow damping rate in tokamaks is reduced approximately by a factor of ∫S∫ when the effects of orbit squeezing are taken into account. Here, S is the orbit-squeezing factor. Thus, the plasma confinement could be improved when the effects of the orbit squeezing are included in the turbulence simulations.