[Table of Contents]

Plasma and Fusion Research

Volume 9, 3401036 (2014)

Regular Articles

Viscosity Effects on Explosive Growth Dynamics of the Nonlinear Resistive Tearing Mode
Ahmad ALI1), Jiquan LI1) and Yasuaki KISHIMOTO1,2)
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
(Received 21 November 2013 / Accepted 18 February 2014 / Published 7 May 2014)

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

DOI: 10.1585/pfr.9.3401036

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This paper may be cited as follows:

Ahmad ALI, Jiquan LI and Yasuaki KISHIMOTO, Plasma Fusion Res. 9, 3401036 (2014).