1. Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga Koen, Kasuga 816-8580, Japan
2. Research Center for Plasma Turbulence, Kyushu University, 6-1 Kasuga Koen, Kasuga 816-8580, Japan
3. WCI Center for Fusion Theory, NFRI, Gwahangno 113, Daejeon 305-333, Korea
4. CMTFO and CASS, UCSD, La Jolla, California 92093, USA
5. Institute for Advanced Study and Research Institute for Applied Mechanics, Kyushu University, Fukuoka 816-8580, Japan