Investigation of Toroidal Acceleration and Potential Acceleration Forces in EAST and J-TEXT Plasmas

Experiments were performed on EAST and J-TEXT for ohmic plasmas with net counter- and co-current toroidal acceleration generated by density ramping-up and ramping-down. Core toroidal rotation is increasing with Te/Ti increasing in observed region (r /a ≤ 0.3). There may be certain correlation between rotation variation and temporal change in density fluctuation intensity. Meanwhile, it is shown that core counter-current toroidal acceleration is gradually increased with the increase of ramp rate in electron density. Direction reversal from co- to counter-current of edge C4+ toroidal rotation is observed by ramp up in electron density. Additionally on EAST, net co-current toroidal acceleration was also formed by LHCD or ICRF. For the current experimental results, toroidal acceleration was between −50 km/s2 in counter-current direction and 70 km/s2 in co-current direction. Eφ may be one of the co-current toroidal forces, which may generate co-current toroidal acceleration,and acts on the plasma as a whole. On the other hand, electron-ion toroidal friction may be one of the counter-current toroidal forces, which may produce counter-current toroidal acceleration, because electrons move in counter-current direction in order to produce a toroidal plasma current.