Role of zonal flows in trapped electron mode turbulence through nonlinear gyrokinetic particle and continuum simulation
- Plasma Science and Fusion Center, Massachusetts Institute of Technology, 167 Albany Street, NW16-258, Cambridge, Massachusetts 02139 (United States)
- Center for Integrated Plasma Studies, University of Colorado, Boulder, Colorado 80309 (United States)
- Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
- Department of Physics and Department of Nuclear Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)
- Department of Physics, Institute for Research in Electronics and Applied Physics, and Center for Scientific Computation and Mathematical Modelling, University of Maryland, College Park, Maryland 20742 (United States)
Trapped electron mode (TEM) turbulence exhibits a rich variety of collisional and zonal flow physics. This work explores the parametric variation of zonal flows and underlying mechanisms through a series of linear and nonlinear gyrokinetic simulations, using both particle-in-cell and continuum methods. A new stability diagram for electron modes is presented, identifying a critical boundary at {eta}{sub e}=1, separating long and short wavelength TEMs. A novel parity test is used to separate TEMs from electron temperature gradient driven modes. A nonlinear scan of {eta}{sub e} reveals fine scale structure for {eta}{sub e} > or approx. 1, consistent with linear expectation. For {eta}{sub e}<1, zonal flows are the dominant saturation mechanism, and TEM transport is insensitive to {eta}{sub e}. For {eta}{sub e}>1, zonal flows are weak, and TEM transport falls inversely with a power law in {eta}{sub e}. The role of zonal flows appears to be connected to linear stability properties. Particle and continuum methods are compared in detail over a range of {eta}{sub e}=d ln T{sub e}/d ln n{sub e} values from zero to five. Linear growth rate spectra, transport fluxes, fluctuation wavelength spectra, zonal flow shearing spectra, and correlation lengths and times are in close agreement. In addition to identifying the critical parameter {eta}{sub e} for TEM zonal flows, this paper takes a challenging step in code verification, directly comparing very different methods of simulating simultaneous kinetic electron and ion dynamics in TEM turbulence.
- OSTI ID:
- 21277151
- Journal Information:
- Physics of Plasmas, Vol. 16, Issue 5; Other Information: DOI: 10.1063/1.3116282; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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