1. A.V. Voronin Laboratory of Magnetohydrodynamic Phenomena, A.F. Ioffe Physico - Technical Institute, Politechnicheskaya, 26, St. Petersburg, 194021, Russia.
2. Fusion Plasma Physics, Alfven Laboratory, Royal Institute of Technology, S-100 44, Stockholm, Sweden
3. Large Tokamak Experiment Division 1, Naka Fusion Reseach Establishment, Japan. Atomic Energy Research Institute, Naka, Ibaraki 319-1195, Japan
4. Department of Physics, Joetsu University of Education, Joetsu, Nigata 943-8512, Japan