Edge Localized Modes have been studied in PBX-M discharges with high data sampling rate magnetic diagnostics with good spatial coverage. High frequency (>or=250 kHz) activity appears prior to the increase in the D alpha emission. While this high frequency activity is global, with high coherence for all coils both on the inside and outside midplane, there is no identifiable mode structure. A very intense outward ballooning feature appears simultaneously with the increase in the D alpha emission, and lasts for about 5 msec. The toroidal mode structure of this feature is clearly identifiable, consisting of a series of toroidal harmonics from n=3 to 8, at frequencies given by f n =f 0 +n Delta f, where Delta f=20-30 kHz and f 0 =30-50 kHz. This feature may be caused by the kinetic ballooning mode.
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Kaye et al. (1994) studied this question.