  Effects of externally applied resonant magnetic perturbation (RMP) on the
locked mode of neo-classical tearing mode (NTM) are numerically investigated by
means of a set of reduced magnetohydrodynamic equations. It is found that for a
small bootstrap current fraction, three regimes, namely slight suppression
regime, small locked island (SLI) regime and big locked island (BLI) regime,
are discovered with the increase of RMP strength. For a much higher bootstrap
current fraction, however, a new oscillation regime appears instead of the SLI
regime, although the other regimes still remain. The physical process in each
regime is analyzed in detail based on the phase difference between NTM and RMP.
Moreover, the critical values of RMP in both SLI and BLI regimes are obtained,
and their dependence on key plasma parameters is discussed as well.
