Effects Of Poloidal Rotation On Zonal Flows In Tokamak Plasmas

In Tokamak plasmas, zonal flows are electrostatic oscillations which are symmetric at both poloidal and toroidal directions with finite radial wavenumber. There exist two different types of zonal flows: the low frequency zonal flows and the geodesic acoustic modes with a limited frequency oscillation. It is widely believed that zonal flow play a very important role in reduction turbulence amplitude as well as the radial transport so that to attain the goal of enhancing the confinement effect.The effects of poloidal rotation on zonal flows are theoretically investigated in this paper. The fundamental model of a plasma system with the poloidal rotation is present by the means of the ideal magnetohydrodynamic equations and the adiabatic assumption for temperature is adopted. The dispersion relation is theoretically deduced in the poloidal rotation plasma system. Then we can deduce the frequencies of zonal flows through solving the dispersion equation we have got, and analyze the effects of plasma poloidal rotation on low frequency zonal flow and the geodesic acoustic mode. It is shown that the frequencies of the geodesic acoustic mode and the sound speed increase with respect to the poloidal Mach number.In addition, the frequencies of zonal flows are work out when the isothermal assumption for temperature is adopted. Then we can reach a conclusion about the changes of zonal flows frequencies with respect to poloidal rotation Mach number. The results show that zonal flows frequencies are different in numerical when we adopted the different assumptions, But the conclusions we have got are similar, which means the frequencies of the geodesic acoustic mode and the sound speed increase with respect to the poloidal Mach number no matter using adiabatic approximation for temperature or the isothermal approximation for temperature.