Experimental observation of multi-scale interactions among kink/tearing modes and high-frequency fluctuations in the HL-2A core NBI plasmas

Multi-scale interactions have been observed recently in the HL-2A core NBI plasmas, including the synchronous coupling between m/n = 1/1 kink mode and m/n = 2/1 tearing mode, nonlinear couplings of TAE/BAE and m/n = 2/1 TM near q = 2 surface, AITG/KBM/BAE and m/n = 1/1 kink mode near q = 1 surface, and between m/n = 1/1 kink mode and high-frequency turbulence. Experimental results suggest that several couplings can exist simultaneously, Alfvenic fluctuations have an important contribution to the high-frequency turbulence spectra, and the couplings reveal the electromagnetic character. Multi-scale interactions via the nonlinear modulation process maybe enhance plasma transport and trigger sawtooth-crash onset.