Edge-localized modes explained as the amplification of scrape-off-layer current coupling

It is shown that the edge-localized modes (ELMs) observed in tokamak H mode discharges can be explained as external magnetohydrodynamic (MHD) mode amplification due to coupling with scrape-off-layer current. The proposed model offers a new ELM mechanism that produces a sharp onset and initial fast growth of magnetic perturbations even when the underlying equilibrium is only marginally unstable for a MHD mode and also a quick quenching after the bursting peak. The theory also reproduces various other ELM features.