[Table of Contents]

Plasma and Fusion Research

Volume 5, 038 (2010)

Rapid Communications

Mechanism of Structure-Driven Nonlinear Instability of Double Tearing Mode in Reversed Magnetic Shear Plasmas
Miho JANVIER, Yasuaki KISHIMOTO and Jiquan LI
Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
(Received 7 June 2010 / Accepted 3 September 2010 / Published 6 October 2010)


The trigger for the nonlinear destabilization of the double tearing mode (DTM), referred to as a structure-driven instability leading to explosive growth and subsequent collapse, is investigated. We use the reduced MHD equations that solve the evolution of perturbations from an equilibrium deformed by two-dimensional magnetic islands during the slow evolution of the quasi-steady nonlinear regime. By examining conditions near marginal stability (under which the explosive growth is not triggered), we have identified a new secondary instability that starts growing when the magnetic energy of the primary fluctuations associated with the islands reaches a critical level. The energy source of this instability is different from that of the linear DTM; it originates in the spatial deformation due to the DTM-driven magnetic islands and is responsible for the subsequent nonlinear destabilization. The growth rate of this secondary instability is found to be proportional to the magnetic energy, suggesting that it exhibits modulational characteristics.


double tearing mode, secondary instability, modulational instability, reduced MHD, magnetic island

DOI: 10.1585/pfr.5.038


  • [1] Z. Chang et al., Phys. Rev. Lett. 77, 3553 (1996).
  • [2] K. Kusano et al., Astrophys. J. 610, 537 (2004).
  • [3] Y. Ishii et al., Phys. Plasmas 7, 4477 (2000).
  • [4] Y. Ishii et al., Phys. Rev. Lett. 89, 205002 (2002).
  • [5] Z.X. Wang et al., Phys. Rev. Lett. 99, 185004 (2007).
  • [6] Z.X. Wang et al., Phys. Plasmas 15, 082109 (2008).
  • [7] M. Janvier et al., to be published in Plasma Fusion Res. 5 Special Issue, ITC-19 (2010).
  • [8] P.L. Pritchett et al., Phys. Fluids 23, 1368 (1980).
  • [9] P.H. Rutherford, Phys. Fluids 16, 1903 (1973).
  • [10] N.F. Loureiro et al., Phys. Rev. Lett. 95, 235003 (2005).

This paper may be cited as follows:

Miho JANVIER, Yasuaki KISHIMOTO and Jiquan LI, Plasma Fusion Res. 5, 038 (2010).