Observations of spontaneous toroidal flow in the LHD

Spontaneous toroidal flows driven by radial electric fields and ion temperature gradients are studied in the Large Helical Device (LHD). The positive radial electric field drives spontaneous flow in the counter-direction at the plasma edge and in the co-direction near the magnetic axis. The difference in the direction of the spontaneous flow between the core and the edge is considered to be due to the difference in the ratio of the helical ripple to the toroidal ripple. It is clearly observed that the ion temperature gradient causes a spontaneous toroidal flow and is expected to be one of the dominant components of the toroidal flows in the high ion temperature discharges in the LHD.