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The nonlinear coupling between gyroradius scale turbulence and mesoscale magnetic islands in fusion plasmas
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Hornsby, W. A., Peeters, A. G., Snodin, A. P., Casson, F. J. (Francis James), Camenen, Y., Szepesi, G., Siccinio, M. and Poli, E. (2010) The nonlinear coupling between gyroradius scale turbulence and mesoscale magnetic islands in fusion plasmas. Physics of Plasmas, Vol.17 (No.9). Article: 092301 . doi:10.1063/1.3467502 ISSN 1070-664X.
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Official URL: http://dx.doi.org/10.1063/1.3467502
Abstract
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. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467502]
| Item Type: | Journal Article | ||||
|---|---|---|---|---|---|
| Subjects: | Q Science > QC Physics | ||||
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||
| Journal or Publication Title: | Physics of Plasmas | ||||
| Publisher: | American Institute of Physics | ||||
| ISSN: | 1070-664X | ||||
| Official Date: | September 2010 | ||||
| Dates: |
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| Volume: | Vol.17 | ||||
| Number: | No.9 | ||||
| Number of Pages: | 9 | ||||
| Page Range: | Article: 092301 | ||||
| DOI: | 10.1063/1.3467502 | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Funder: | Engineering and Physical Sciences Research Council (EPSRC) | ||||
| Grant number: | EP/H002081/1 (EPSRC) |
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