Simulation study of toroidal flow generation by ECH in non-axisymmetric toroidal plasmas

Spontaneous flows have been observed during ECH with no direct momentum input in tokamak and helical plasmas. In LHD, when we applied ECH to the NBI heated plasma, the toroidal velocity profile changed drastically. We assume that the radial flux of supra-thermal electron enhances the bulk ion cancelling current. This current generates the JxB torque, which would play an essential role in causing a toroidal flow.
In this study, we study the JxB torque due to the radial current of supra-thermal electrons and the collisional torque by the supra-thermal electrons in the LHD using GNET code, which can solve the 5D drift kinetic equation for supra-thermal electrons. As a result, we find that the JxB torque generated by ECH is several times larger than the collisional torque of the supra-thermal electrons and the total torque by ECH is the same order as the NBI torque. Also, its direction is opposite (same) direction to NBI torque in the inner (outer) region, those are consistent with the experimental observations.
Also, we evaluate the torque by ECH in the non-axisymmetric tokamaks (finite toroidal field ripples and magnetic perturbations). We find that the significant torque by ECH is obtained in the case the toroidal field ripple > 0.2%.