Turbulent stabilization of the tearing mode in tokamak plasmas
作者:
E. Esarey,
J. P. Freidberg,
K. Molvig,
C. O. Beasley,
W. I. Van Rij,
期刊:
Physics of Fluids(00319171)
(AIP Available online 1986)
卷期:
Volume 29,
issue 1
页码: 200-211
ISSN:0031-9171
年代: 1986
DOI:10.1063/1.865977
出版商: AIP
数据来源: AIP
摘要:
The effect of turbulent electron diffusion from stochastic electron orbits on the stability of low‐beta fluctuations is considered through the use of the normal stochastic approximation. A set of coupled, self‐adjoint equations is derived for the fluctuation potentials &fgr;˜ andA˜∥. Solutions to this set of equations describe both unstable finite‐&bgr; drift waves when analyzed for high‐mmodes and the tearing mode when analyzed for low‐mmodes. For the tearing mode, it is shown that stability is obtained for sufficiently large values of the diffusion coefficient. ProvidedDe∼1/n, this implies that a density threshold must be surpassed before the tearing mode is observed. Physically, turbulent electron diffusion prohibits the formation of a perturbed current within a finite region about the rational surface. At higher densities, the inclusion of a finite electrostatic potential &fgr;˜ gives an additional stabilizing term to the dispersion relation, which physically represents ion inertial effects. This ion inertial effect implies that, in the absence of diffusion, the tearing mode is stabilized for ion betas &bgr;iabove some critical value.
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