This paper reports the recent observation of a weakly coherent mode (WCM) within a conventional reflectometer on EAST and successfully determines its poloidal wavenumber range. During the transition from the L-mode to I-mode, the line-averaged density remains nearly unchanged while a significant change is observed in the electron cyclotron emission (ECE) signals at the boundary. The difference between the signals for the two channels at the edge increased, coinciding with the appearance of the WCM and a simultaneous rise in the boundary electron temperature. Further investigation unveiled the modulating role of edge temperature ring oscillation (ETRO) (Liu et al 2020 Nucl. Fusion60 126016) on high-frequency density fluctuations. Statistical results unveil an inverse relationship between the centeral frequency of the WCM and q95. Simulation results provide additional insights, demonstrating that the simulated 'WCM' in the density fluctuations aligns with experimental data in terms of center frequency. Additionally, the radial distribution of the simulated 'WCM' closely corresponds to regions with the strongest electron temperature gradients. Finally, through a cross-correlation analysis of the simulated fluctuations, the following phase relationship for the wavenumber range of 'WCM' was observed: .
This paper investigates the weakly coherent mode (WCM) observed in the I-mode regime on the EAST tokamak. The WCM is linked to edge temperature fluctuations and its frequency is inversely related to the safety factor. Simulations provide insights into the WCM's characteristics, aligning with experimental data.