Toroidal Flow Generation by the ICRF Minority Heating and RF Wave Field Profile Dependence

The toroidal flow generation by the ICRF minority heating is investigated in the Alcator C-Mod like tokamak plasma applying GNET code, in which the drift kinetic equation is solved in 5D phase-space. An asymmetry of velocity distribution function in the parallel direction is found and two kinds of toroidal flows are observed. One is the sheared flow near the RF power absorption region depending on the sign of k(parallel to) and the other is the toroidal flow, which is larger than the previous one, independent of the sign of k(parallel to). It is found that the k(parallel to) sign dependent flow would be related to the mechanism proposed by Ohkawa et al. [Phys. Plasmas 12 (2005) 094506.] and that the k(parallel to) sign independent toroidal flow is generated by the net toroidal motion of energetic tail ions. We also investigate the effect of RF wave field profile on the toroidal flow generation comparing the local and broad heating cases. A broader toroidal flow is obtained and about 5 times of ICRF heating power is necessary for generating the similar amplitude of toroidal flow in the broad heating case.