Characterization of inter-ELM Burst Activities in the Pedestal*

We investigate the inter-ELM stage during which multiple pedestal localized modes have been observed to be correlated with pedestal density and temperature prior to the ELM onset. We report on bursting activities of high frequency modes (~350 kHz) which appear between ELMs. These bursts have also been observed in JET ILW (Bowman et al. NF 58 016021 2018) and in AUG (Hennequin et al. EPS 2017 P1.167). The low frequency modes remain unchanged during these bursts. The high frequency mode's onset is correlated with the pedestal density gradient and localized in the steep gradient region. The bursts are detected using BES, DBS, and magnetic probes. The bursts have an effect on the pedestal temperature evolution, while the pedestal density evolution remains unmodified. This clearly suggests that the bursts provide mainly electron heat transport. Bicoherence analysis shows that the bursts result from nonlinear interactions of pedestal localized modes. Analysis of connection between bursts and an ELM event (hypothesized  to be multi-mode interactions) will be discussed.