Radial interchange motions of plasma filaments

Garcia, O.E., Bian, N.H. and Fundamenski, W. (2006) Radial interchange motions of plasma filaments. Physics of Plasmas, 13(8), Art. 082309. (doi: 10.1063/1.2336422)

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Abstract

Radial convection of isolated filamentary structures due to interchange motions in magnetized plasmas is investigated. Following a basic discussion of vorticity generation, ballooning, and the role of sheaths, a two-field interchange model is studied by means of numerical simulations on a biperiodic domain perpendicular to the magnetic field. It is demonstrated that a blob-like plasma structure develops dipolar vorticity and electrostatic potential fields, resulting in rapid radial acceleration and formation of a steep front and a trailing wake. While the dynamical evolution strongly depends on the amount of collisional diffusion and viscosity, the structure travels a radial distance many times its initial size in all parameter regimes in the absence of sheath dissipation. In the ideal limit, there is an inertial scaling for the maximum radial velocity of isolated filaments. This velocity scales as the acoustic speed times the square root of the structure size relative to the length scale of the magnetic field. The plasma filament eventually decelerates due to mixing and collisional dissipation. Finally, the role of sheath dissipation is investigated. When included in the simulations, it significantly reduces the radial velocity of isolated filaments. The results are discussed in the context of convective transport in scrape-off layer plasmas, comprising both blob-like structures in low confinement modes and edge localized mode filaments in unstable high confinement regimes.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Bian, Dr Nicolas Horace
Authors: Garcia, O.E., Bian, N.H., and Fundamenski, W.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physics of Plasmas
Publisher:American Institute of Physics
ISSN:1070-664X
ISSN (Online):1089-7674

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