Spectral characteristics of edge magnetic turbulence in COMPASS-D

Edge fluctuation data from both COMPASS-D and calculations with the large-e ddy simulation code CUTIE have been analysed with a number of techniques, r evealing coherent structures which exhibit high-frequency, standing-wave os cillations; some of those observed during edge localized modes (ELMs) have an 'inverse-chirp' character and these are related to a disturbance of the plasma boundary in the lower-inboard quadrant of the poloidal plane. A 'pre cursor' mode, seen in Ohmic discharges at about 220 kHz just before large E LMs, appears to be outward ballooning in character. Although the CUTIE calc ulations do not yet include ELM simulations, the results seem to correspond qualitatively with those seen between ELMs or during ELM-free periods on C OMPASS-D.