The synergistic effect between the radial electric field (Er) shear and the magnetic shear on the ion temperature gradient (ITG) mode in a Experimental Advanced Superconducting Tokamak discharge has been investigated using gyrokinetic simulations. The stabilizing or destabilizing effect of the Er 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 the 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 the Er shear suppresses the ITG turbulence and highlight the enhanced suppression of the ITG turbulence by the negative shearing rate under the weakly reversed magnetic shear. Based on the experimental Er profile, it is shown that the geometric effect of Er on the stabilization of micro-instabilities needs to be considered. The relative position between the bottom of the well-like experimental Er and the ITG mode is crucial for effectively stabilizing the ITG mode, highlighting the synergistic effect between the Er shear and the magnetic shear on the ITG mode.
This paper investigates how the radial electric field (Er) and magnetic shear affect the ion temperature gradient (ITG) mode in a tokamak. The results show that the stabilizing or destabilizing effect of Er shear depends on its magnitude and alignment with the magnetic shear. Negative Er shear can effectively suppress ITG turbulence under weakly reversed magnetic shear. The relative position of Er and ITG mode is crucial for stabilization.