Plasma and Fusion Research
Volume 1, 024 (2006)
Letters
- 1)
- Graduate School of Energy Science, Kyoto University
- 2)
- Naka Fusion Research Establishment
- 3)
- Southwestern Institute of Physics
Abstract
The effects of an external mean flow on the generation of zonal flow in drift wave turbulence are theoretically studied in terms of a modulational instability analysis. A dispersion relation for the zonal flow instability having complex frequency ωq = Ωq + iγq is derived, which depends on the external mean flow's amplitude |φf| and radial wave number kf. As an example, we chose an ion temperature gradient (ITG) turbulence-driven zonal flow as the mean flow acting on an electron temperature gradient (ETG) turbulence-zonal flow system. The growth rate of the zonal flow γq is found to be suppressed, showing a relation γq = γq0(1-α|φf|2kf2 ), where γq0 is the growth rate in the absence of mean flow and α is a positive numerical constant. This formula is applicable to a strong shearing regime where the zonal flow instability is stabilized at α|φf2|kf2 ≈ 1. Meanwhile, the suppression is accompanied by an increase of the real frequency |Ωq|. The underlying physical mechanism of the suppression is discussed.
Keywords
drift wave turbulence, zonal flow, mean plasma flow, modulational instability
Full Text
References
- [1] P.H. Diamond, S.-I. Itoh, K. Itoh and T.S. Hahm, Plasma Phys. Control. Fusion 47, R35 (2005).
- [2] A. Hasegawa and M. Wakatani, Phys. Rev. Lett. 59, 1581 (1987).
- [3] L. Chen, Z. Lin and R. White, Phys. Plasmas 7, 3129 (2000).
- [4] J.Q. Li and Y. Kishimoto, Phys. Plasmas 12, 054505 (2005).
- [5] N. Miyato, Y. Kishimoto and J.Q. Li, Phys. Plasmas 11, 5557 (2004).
- [6] T.S. Hahm and K.H. Burrell, Phys. Plasmas 3, 427 (1996).
- [7] Y. Kishimoto, J.Y. Kim, W. Horton, T. Tajima, M.J. LeBrun and H. Shirai, Plasma Phys. Control. Fusion 41, A663 (1999).
- [8] E. Kim and P. Diamond, Phys. Plasmas 10, 1698 (2003).
- [9] A. Hasegawa and K. Mima, Phys. Fluids 21, 87 (1978).
- [10] T.S. Hahm, M.A. Beer, Z. Lin, G.W. Hammett, W.W. Lee and W.M. Tang, Phys. Plasmas 6, 922 (1999).
This paper may be cited as follows:
Ken UZAWA, Yasuaki KISHIMOTO and Jiquan LI, Plasma Fusion Res. 1, 024 (2006).