The rotation profile effects on self-suppressing double tearing modes (DTMs) via Alfvén resonance in rotating tokamak plasmas with reversed magnetic shear are numerically investigated using a reduced magnetohydrodynamic model. The synergetic effects of Alfvén resonance and flow shear on suppressing the DTMs are addressed. It is found that the Alfvén resonances on both sides of the inner rational surface rs1 decouple the strongly coupled DTMs, and simultaneously the flow shear further stabilizes the tearing instability on the outer rational surface rs2. When the tearing instability on rs2 is stabilized so significantly that it becomes less unstable than the original one on rs1, a new mode transition occurs, in which the tearing instability excitation switches from rs2 to rs1; meanwhile, the Alfvén resonances switch from both sides of rs1 to both sides of rs2. Moreover, the characteristics of the two eigenmode patterns of the DTM-induced Alfvén resonances are analysed in detail. In addition, it is observed that the critical rotation frequency of the mode transition is almost independent of resistivity.
Measurements, modelling and electron cyclotron heating modification of Alfvén eigenmode activity in DIII-D