  A gyrokinetic simulation of the influence of electron cyclotron current drive
and ion kinetic effect on the m/n=2/1 tearing mode (TM) instabilities is
presented in HL-2A and DIII-D tokamak configurations. The TM evolution is
calculated with a finite mass electron model and the rf current source is
obtained by ray-tracing and the Fokker-Planck method. The TMs are found to be
perfectly stabilized by a continuous 1MW 68GHz X2-mode in HL-2A tokamak, while
instabilities in the DIII-D discharge (with lower value of CR=I_{rf}/I_{0},
where Irf is the wave driven current and I0 is the equilibrium plasma current)
are only partially stabilized with the 1MW 110GHz X2-mode due to inadequate
power input. The result also indicates that a helicon current drive is more
efficient than a continuous ECCD. Analysis of the GTC simulation reveals, both
in HL-2A and DIII-D, that the presence of ions can reduce the island width as
well as the growth rate. Furthermore, the kinetic effect of thermal ions on TM
is found to be more pronounced with higher ion temperature.
