Measurements and simulations of quasi-coherent fluctuations during the inter-ELM phase in EAST

Quasi-coherent fluctuations have been commonly observed preceding type-I ELMs in EAST. They typically show up in two frequency domains. The lower frequency band (30-50 kHz) propagates in ion diamagnetic direction. It predominantly peaks on low field side, but not evidently contribute to local transport. The higher frequency band (180--220 kHz) is detected to propagate in the electron diamagnetic direction. Its amplitude exhibits an in-out symmetry. However, it drives strong particle transport into far SOL region on high field side. Study of these inter-ELM fluctuations are important for our understanding of pedestal physics,SOL width and ELM process itself. For this purpose, BOUT$++$ simulations for inter-ELM fluctuations are conducted based on EAST experiments. The preliminary simulation results suggest that peeling-ballooning and drift-alfven instabilities could be respectively responsible for the lower frequency band and higher frequency band fluctuations observed during the inter-ELM phase in experiments.Comparison of nonlinear simulations with experimental measurements will be presented.