Direct observation of current in type I ELM filaments on ASDEX Upgrade

Magnetically confined plasmas are often subject to relaxation oscillations accompanied by large transport events. This is particularly the case for the high confinement regime of tokamaks where these events are termed edge localized modes (ELMs). Present ELM theories rely on a combined effect of edge current and the edge pressure gradients which result in intermediate mode number (n ∼= 10−15) structures (filaments) localized in the perpendicular plane and extended along the field lines. By detailed localized measurements of the magnetic field perturbation associated to type I ELM filaments it is shown that these filaments carry a substantial current. PACS numbers: 52.35.PY 52.55.Fa 52.55.RK 52.70.Ds