Plasma and Fusion Research
Volume 9, 3401036 (2014)
Regular Articles
- 1)
- Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
- 2)
- Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
Abstract
A collapse of the X-point occurs above a critical island width, Δ'wc, in the resistive tearing mode for large instability parameter, Δ', leading to current sheet formation [N.F. Loureiro et al. Phys. Rev. Lett. 95, 235003 (2005)]. In this study, we analyze this problem by including viscosity effects on the onset of the X-point collapse and the explosive nonlinear growth dynamics of the reconnected flux. While explosive growth seems to be independent of viscosity in the magnetic Prandtl number regime Pr < 1, a transition behavior is revealed at Pr ≈ 1 for the viscosity dependence of Δ'wc, for the X-point collapse as well as the linear tearing instability. A secondary instability analysis, which included quasi-linear modifications of the equilibrium current profile due to the zonal current, shows that current peaking is plausibly responsible for the onset of the X-point collapse and the explosive growth of reconnected flux, which leads to the current sheet formation.
Keywords
resistive tearing mode, viscosity, X-point collapse, critical island width, secondary instability analysis
Full Text
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This paper may be cited as follows:
Ahmad ALI, Jiquan LI and Yasuaki KISHIMOTO, Plasma Fusion Res. 9, 3401036 (2014).