Physics

LINEAR AND NONLINEAR STUDIES OF TRAPPED ELECTRON MODE TURBULENCE. Michael D Hoffman1, Darin R Ernst*2, University of Missouri – Rolla1, Department of Physics, Rolla, MO 65409, Plasma Science and Fusion Center2, Massachusetts Institute of Technology, Cambridge, MA 02139, HYPERLINK "mailto:dernst@psfc.mit.edu" dernst@psfc.mit.edu

Linear stability diagrams are presented to clarify the onset of toroidal drift modes, including ITG, and resonant and non-resonant TEMs, as a function of density and temperature gradients. Nearly two thousand linear gyrokinetic stability analysis were performed with the GS2 code to generate a stability diagram, varying density and temperature gradients around the "Cyclone Base Case." A series of nonlinear gyrokinetic simulations have been carried out to analyze the anisotropy of the turbulent eddies, and the role of zonal flows, as a function of drive. Two separate studies have previously found that zonal flows play very different roles in TEM turbulence. The first [1], found that zonal flows play a strong role near threshold, where they produce a nonlinear upshift. The second [2], for a case well above threshold, found that zonal flows have little effect on the turbulent saturation level. Our results show that the anisotropy depends on the type and strength of the drive. 1) D. R. Ernst et al., Phys. Plasmas 11(5) (2004) 2637. Also IAEA-CN-149/TH/1-3 (2006). 2) T. Dannert et al., Phys. Plasmas 12 (2005) 072309.

Funding was provided by DOE National Undergraduate Fellowship in Plasma Science and Fusion Energy.