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Title: Nonadiabatic electron response in the Hasegawa-Wakatani equations

Tokamak edge turbulence is strongly influenced by parallel electron physics, which relaxes density and potential fluctuations towards electron adiabatic response. Beginning with the paradigmatic Hasegawa-Wakatani equations (HWEs) for resistive tokamak edge turbulence, a unique decomposition of the electric potential (φ) into adiabatic (a) and nonadiabatic (b) portions is derived, based on the requirement that a neither drive nor respond to the parallel current j{sub ∥}. The form of the decomposition clarifies that, at perpendicular scales large relative to the sound radius, the electron adiabatic response controls the nonzonal φ, not the fluctuating density n. Simple energy balance arguments allow one to rigorously bound the ratio of rms nonzonal nonadiabatic fluctuations (b(tilde sign)) relative to adiabatic ones (ã). The role of the vorticity nonlinearity in transferring energy between adiabatic and nonadiabatic fluctuations aids intuitive understanding of self-sustained turbulence in the HWEs. When the normalized parallel resistivity is weak, b(tilde sign) becomes effectively slaved, allowing the reduction to an approximate one-field model that remains valid for strong turbulence. In addition to guiding physical intuition, the one-field reduction should greatly ease further analytical manipulations. Direct numerical simulation of the 2D HWEs confirms the convergence of the asymptotic formula for b(tilde sign)
Authors:
 [1] ;  [2] ;  [3]
  1. Max-Planck-Institut für Plasmaphysik, EURATOM Association, Teilinstitut Greifswald, Wendelsteinstr. 1, 17491 Greifswald (Germany)
  2. Max-Planck-Institut für Plasmaphysik, EURATOM Association, Boltzmannstraße 2, 85748 Garching (Germany)
  3. PPPL, Princeton University, P.O. Box 451, MS 28, Princeton, New Jersey 08543–0451 (United States)
Publication Date:
OSTI Identifier:
22227901
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 8; Other Information: (c) 2013 EURATOM; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; APPROXIMATIONS; BOUNDARY LAYERS; COMPUTERIZED SIMULATION; ELECTRIC POTENTIAL; ELECTRONS; FLUCTUATIONS; NONLINEAR PROBLEMS; NUMERICAL ANALYSIS; PLASMA CONFINEMENT; PLASMA DENSITY; SOUND WAVES; TOKAMAK DEVICES; TURBULENCE