Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence

[摘要] Virtually, all existing theoretical works on turbulent poloidal momentum transport are based on quasilinear theory. Nonlinear poloidal momentum flux—langle {{ilde{v}}_{r}}ilde{n}{{ilde{v}}_{heta}}rangleis universally neglected. However, in the strong turbulence regime where relative fluctuation amplitude is no longer small, quasilinear theory is invalid. This is true at the all-important plasma edge. In this work, nonlinear poloidal momentum flux langle {{ilde{v}}_{r}}ilde{n}{{ilde{v}}_{heta}}ranglein strong electrostatic turbulence is calculated using the Hasegawa–Mima equation, and is compared with quasilinear poloidal Reynolds stress. A novel property is that symmetry breaking in fluctuation spectrum is not necessary for a nonlinear poloidal momentum flux. This is fundamentally different from the quasilinear Reynold stress. Furthermore, the comparison implies that the poloidal rotation drive from the radial gradient of nonlinear momentum flux is comparable to that from the quasilinear Reynolds force. Nonlinear poloidal momentum transport in strong electrostatic turbulence is thus not negligible for poloidal rotation drive, and so may be significant to transport barrier formation.

[关键词] poloidal rotation;nonlinear poloidal momentum flux;strong turbulence;Reynolds stress