[Table of Contents]

Plasma and Fusion Research

Volume 10, 1203014 (2015)

Rapid Communications

Nonlinear Stability of Externally Induced Magnetic Islands in Multi-Helicity Helical Systems
Seiya NISHIMURA
Kobe City College of Technology, Kobe 651-2194, Japan
(Received 4 January 2015 / Accepted 9 February 2015 / Published 27 February 2015)

Abstract

Self-healing (spontaneous shrinkage) of externally induced magnetic islands is a critical issue in helical systems, where helical ripple-induced neoclassical viscous torques play essential roles. In this study, effective helical ripple rates of magnetic fields in multi-helicity helical systems are revisited. In a typical parameter regime of the Large Helical Device, effective helical ripple rates are sensitive to magnetic axis positions. An extended theory of the self-healing taking into account effective helical ripple rates is firstly developed. It is newly found that self-healing thresholds considerably depend on magnetic axis positions, which is due to neoclassical viscous torques depending on effective helical ripple rates.

Keywords

magnetohydrodynamics, neoclassical transport, resonant magnetic perturbation, magnetic island, helical system

DOI: 10.1585/pfr.10.1203014

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This paper may be cited as follows:

Seiya NISHIMURA, Plasma Fusion Res. 10, 1203014 (2015).