Effect of Ion Sound Larmor Radius on Collisionless MHD Modes
Taro Matsumotoa, Shinji Tokudaa, Yasuaki Kishimotoa and Hiroshi Naitoub
a) Japan Atomic Energy Research Institute, Ibaraki, 311-0193, Japan
b) Yamaguchi University, Ube, Yamaguchi 755-8611, Japan
Abstract.
As the plasma temperature is getting higher, besides the resistivity of plasma, kinetic effects due to the particle properties of plasma such as the electron inertia come to play an important role on the MHD modes. In order to clarify the effect of the electron inertia on the nonlinear behavior of MHD phenomena in tokamak plasmas, the m=1 collisionless kink mode and the m=2 collisionless double tearing mode have been studied with the gyro-kinetic particle simulation[1]. The nonlinear effect of the density gradient on the collisionless kink mode is also studied[2]. However, the ratio of the ion Larmor radius estimated with electron temperature to the electron skin depth was restricted to be less than one, ρs/δe << 1, due to the limit of computational resource.
In this research, the restriction for the ion Larmor radius is relaxed to be ρs/δe ~ 1 by the realization of the massively parallel computing. Then, the effect of finite Larmor radius on the collisionless MHD modes comes to be understood. It is found that although the linear growth rate is decreased, the internal collapse is induced due to the lack of dissipation. It is also found that the maximum value of the electrostatic potential is reduced, therefore, the nonlinear behavior after the internal collapse is affected. Furthermore, the nonlinear effect of the density gradient is also studied. The details will be shown at the conference.
[1] T. Matsumoto, H. Naitou, S. Tokuda, Y. Kishimoto, 18th IAEA Fusion Energy Conference, Sorrento, Italy, 2000, IAEA-CN-77/TH3/3.
[2] T. Matsumoto, S. Tokuda, Y. Kishimoto, T. Takizuka, H. Naitou, J. Plasma and Fusion Res. Series Vol.2, (1999) 97.