The nonlinear coupling between gyroradius scale turbulence and mesoscale magnetic islands in fusion plasmas

Journal Article · Wed Sep 15 00:00:00 EDT 2010 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3467502· OSTI ID:21432271

Hornsby, W A; Peeters, A G; Snodin, A P; Casson, F J; Camenen, Y; Szepesi, G ^[1]; Siccinio, M; Poli, E ^[2]

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1. Department of Physics, Centre for Fusion, Space, and Astrophysics, University of Warwick, Coventry (United Kingdom)
2. Max-Planck-Institut fuer Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching bei Muenchen (Germany)

The interaction between small scale turbulence (of the order of the ion Larmor radius) and mesoscale magnetic islands is investigated within the gyrokinetic framework. Turbulence, driven by background temperature and density gradients, over nonlinear mode coupling, pumps energy into long wavelength modes, and can result in an electrostatic vortex mode that coincides with the magnetic island. The strength of the vortex is strongly enhanced by the modified plasma flow response connected with the change in topology, and the transport it generates can compete with the parallel motion along the perturbed magnetic field. Despite the stabilizing effect of sheared plasma flows in and around the island, the net effect of the island is a degradation of the confinement. When density and temperature gradients inside the island are below the threshold for turbulence generation, turbulent fluctuations still persist through turbulence convection and spreading. The latter mechanisms then generate a finite transport flux and, consequently, a finite pressure gradient in the island. A finite radial temperature gradient inside the island is also shown to persist due to the trapped particles, which do not move along the field around the island. In the low collisionality regime, the finite gradient in the trapped population leads to the generation of a bootstrap current, which reduces the neoclassical drive.

• OSTI ID: 21432271
• Journal Information: Physics of Plasmas, Vol. 17, Issue 9; Other Information: DOI: 10.1063/1.3467502; (c) 2010 American Institute of Physics; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BOOTSTRAP CURRENT
CONVECTION
COUPLING
ELECTRON TEMPERATURE
ION TEMPERATURE
MAGNETIC ISLANDS
NONLINEAR PROBLEMS
PLASMA
PLASMA DENSITY
PRESSURE GRADIENTS
TEMPERATURE GRADIENTS
TURBULENCE
VORTICES
CURRENTS
ELECTRIC CURRENTS
ENERGY TRANSFER
HEAT TRANSFER
MAGNETIC FIELD CONFIGURATIONS
MASS TRANSFER