Zonal flow generation and its nonlinear dynamics in trapped electron mode turbulence of flat density tokamak plasmas. (25th May 2016)

• Record Type: Journal Article
• Authors: Guo, Z.B.; Hahm, T.S.
• Is Part Of: Nuclear fusion. Volume 56:Number 6(2016:Jun.)
• Publication Date: 2016-05-25
• Subjects: zonal flow -- flat density -- TEM; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/0029-5515/56/6/066014
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: We investigate zonal flow (ZF) generation in ion temperature gradient driven trapped-electron-mode (ITG-driven TEM) turbulence via modulational instability analysis. We show that the acceleration of a seed ZF is a consequence of the competition of negative radiation pressure (NRP, acting as a driving force) and positive radiation pressure (PRP, acting as a retarding force) of the ITG-driven TEM turbulence. A critical dimensionless ion temperature logarithmic gradient ( R / L T i, c ) normalized to the major radius is obtained by balancing the NRP- and PRP effects. For R L T i < R L T i, c, the NRP effect is dominant and the seed ZF is accelerated. Otherwise, the PRP effect is dominant and the seed ZF is decelerated. In addition, a new nonlinear evolution mechanism of the ZF is also proposed. It is shown that the turbulence energy intensity spectrum gets steepened in k -space due to the ZF shearing, which in turn induces nonlinear growth of the ZF.