Multiple resonances in the edge-localized mode (ELM) frequency (f ELM ) as a function of the edge safety factor q 95 have been observed for the first time with an applied low n (¼1; 2) field on the JET tokamak. Without an n ¼ 1 field applied, f ELM increases slightly from 20 to 30 Hz by varying the q 95 from 4 to 5 in a type-I ELMy H-mode plasma. However, with an n ¼ 1 field applied, a strong increase in f ELM by a factor of 4-5 has been observed with resonant q 95 values, while the f ELM

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... sed only by a factor of 2 for nonresonant values. A model, which assumes that the ELM width is determined by a localized relaxation triggered by an unstable ideal external peeling mode, can qualitatively predict the observed resonances when low n fields are applied.