[Table of Contents]

Plasma and Fusion Research

Volume 5, 002 (2010)

Regular Articles

Magnetic Island Formation by External Cyclic Perturbation in Rotating and Non-rotating Plasmas
Yasutomo ISHII
Japan Atomic Energy Agency, Ibaraki 311-0193, Japan
(Received 21 July 2009 / Accepted 8 October 2009 / Published 25 January 2010)

Abstract

Effects of a non-monotonically evolving external perturbation on a plasma, that is stable against tearing modes, are numerically investigated. It is found that for a magnetic island driven by an external single-cycle magnetic perturbation, the time constants during the phases of growth and decay are different. This difference in time constants causes a finite magnetic island to form even after the external perturbation is removed. Therefore, the saturation width of a magnetic island driven by a successive applications of an external single-cycle perturbation becomes larger than the maximum magnetic island width driven by a single application of that. For a rotating plasma, the background rotation is damped as the magnetic island grows due to an external perturbation [R. Fitzpatrick, Phys. Plasmas 5, 3325(1998)]. Therefore, for a rotating plasma, the driven magnetic island can enter an explosive growth stage due to successive applications of a single-cycle perturbation even with amplitude smaller than the critical value for the onset of the rapid growth in the case of a monotonically increasing or step-function type external perturbation. These features are important in explaining the explosive growth of magnetic islands and the onset of neoclassical tearing mode due to non-monotonically growing MHD phenomena such as sawtooth, fishbones and ELM.

Keywords

magnetic island, plasma rotation, external perturbation, neoclassical tearing mode, sawtooth

DOI: 10.1585/pfr.5.002

Full Text

PDF format (924Kbytes) PDF Download

References

  • [1] R. Carrera, R.D. Hazeltine and M. Kotschenreuther, Phys. Fluids 29, 899 (1986).
  • [2] A.M. Garofalo et al., Phys. Rev. Lett. 89, 235001 (2002).
  • [3] R.A. Moyer et al., Phys. Plasmas 12, 056119 (2005).
  • [4] F. Wagner et al., Phys. Rev. Lett. 49, 1408 (1982).
  • [5] R. Fitzpatrick, Phys. Plasmas 5, 3325 (1998).
  • [6] R. Fitzpatrick, Phys. Plasmas 10, 1782 (2003).
  • [7] Y. Ishii et al., Nucl. Fusion 47, 1024 (2007).
  • [8] S. von Goeler, W. Stodiel and N. Sauthoff Phys. Rev. Lett. 33, 1201 (1974).
  • [9] H.R. Strauss et al., Phys. Fluids 19, 134 (1982).
  • [10] A. Hasegawa and L. Chen, Phys. Rev. Lett. 32, 454 (1974).
  • [11] X. Wang et al., Phys. Plasmas 5, 2291 (1998).
  • [12] Y. Ishii and A. Smolyakov, Plasma Fusion Res. 3, 048 (2008).
  • [13] O. Sauter et al., Phys. Rev. Lett. 88, 105001 (2002).
  • [14] R.J. Buttery et al., Nucl. Fusion 44, 69 (2003).
  • [15] M.F.F. Nave et al., Nucl. Fusion. 43, 179 (2003).
  • [16] R.J. Buttery et al., Phys. Rev. Lett. 88, 125005 (2002).
  • [17] R.C. Wolf et al., Plasma Phys. Control Fusion 41, B93 (1999).
  • [18] A. Gude et al., Nucl. Fusion. 42, 53 (2000).
  • [19] R.L. La Haye et al., Nucl. Fusion. 40, 53 (2000).
  • [20] O. Sauter et al., Phys. Plasmas 4, 1654 (1997).

This paper may be cited as follows:

Yasutomo ISHII, Plasma Fusion Res. 5, 002 (2010).