Synergistic effect between radial electric field and magnetic shear on ion temperature gradient mode

The synergistic effect between the radial electric field ( E r ) shear and the magnetic shear on ion temperature gradient (ITG) mode in a Experimental Advanced Superconducting Tokamak (EAST) discharge has been investigated using gyrokinetic simulations. The stabilizing or destabilizing effect of the E r shear depends on both its magnitude and its directional alignment with the magnetic shear, with a negative shearing rate exhibiting a more efficient stabilizing influence under weakly reversed magnetic shear because both effects tilt the ITG mode structure in the same direction. Nonlinear simulations reveal a threshold in shearing rate beyond which E r shear suppresses ITG turbulence and highlight the enhanced suppression of ITG turbulence by negative shearing rate under weakly reversed magnetic shear. Based on the experimental E r profile, it is shown that the geometric effect of E r on the stabilization of micro-instabilities needs to be considered. The relative position between the bottom of the well-like experimental E r and the ITG mode is crucial for effectively stabilizing the ITG mode, highlighting the synergistic effect between the E r shear and the magnetic shear on ITG mode.