The residual zonal flow in tokamak plasmas toroidally rotating at arbitrary velocity

Abstract

Zonal flows, initially driven by ion-temperature-gradient turbulence, may evolve due to the neoclassic polarization in a collisionless tokamak plasma. In our previous work [D. Zhou, Nucl. Fusion 54, 042002 (2014)], the residual zonal flow in a tokamak plasma rotating toroidally at sonic speed is found to have the same form as that of a static plasma. In the present work, the form of the residual zonal flow is presented for tokamak plasmas rotating toroidally at arbitrary velocity. The gyro-kinetic equation is analytically solved for low speed rotation to give the expression of residual zonal flows, and the expression is then generalized for cases with arbitrary rotating velocity through interpolation. The zonal flow level decreases as the rotating velocity increases. The numerical evaluation is in good agreement with the former simulation result for high aspect ratio tokamaks.

The residual zonal flow in tokamak plasmas with a poloidal electric field

“…Sugama and Watanabe studied the dynamics of ZFs in helical systems [10]. The evolution of ZFs in a toroidally rotating plasma was numerically simulated by Casson et al [11], and an analytical expression of flow residual in a large aspect ratio toroidally rotating tokamak was given by Zhou [12,13]. The RZF level decreases with the increasing rotating velocities.…”