skip to main content

SciTech ConnectSciTech Connect

Title: Shear flow instabilities induced by trapped ion modes in collisionless temperature gradient turbulence

One important issue in turbulence self-organization is the interplay between the Kelvin–Helmholtz (KH) instability and streamers and/or zonal flows. This question has been debated for a long time. The effects of the KH instability and its position in the sequence of events between streamers, turbulence, and zonal flows have been investigated with a reduced gyro-bounce averaged kinetic code devoted to study the primary ion temperature gradient (ITG) instability linked to trapped ion modes (TIM). In toroidal geometry, the specific dynamics of TIM linked to trapped particles becomes important when the frequency of ITG modes falls below the ion bounce frequency, allowing one to average on both the cyclotron and bounce motion fast time scales. This reduction of the number of degrees of freedom leads to a strong reduction of computer resources (memory and computation time). Bounce-averaged gyrokinetic code can be considered as a toy model able to describe basic structures of turbulent transport in tokamak devices. In particular, by means of this code, we have observed that the energy injected in the system by the TIM instability is exchanged between streamers and zonal flows by means of KH vortices that grow along these structures in the nonlinear phase. The energymore » transfer occurs throughout the relaxation phase of the streamer growth leading to a modification of the KH modes and to the generation of the zonal flows.« less
Authors:
 [1] ;  [2] ; ; ; ; ;  [1] ;  [3]
  1. CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France)
  2. (France)
  3. Institut Jean Lamour-UMR 7168, Université de Lorraine, 54506 Vandoeuvre les Nancy (France)
Publication Date:
OSTI Identifier:
22408305
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 4; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; DEGREES OF FREEDOM; ENERGY TRANSFER; HELMHOLTZ INSTABILITY; INSTABILITY; ION TEMPERATURE; NONLINEAR PROBLEMS; RELAXATION; SHEAR; TEMPERATURE GRADIENTS; TOKAMAK DEVICES; TRAPPED-PARTICLE INSTABILITY; TURBULENCE; VORTICES