Rotating resonant magnetic perturbation (RMP) fields impose a characteristic modulation to the edge electron density ne(r, t) and temperature Te(r, t) fields, which depends on the relative rotation frel between external RMP field and plasma fluid. The ne(r, t) and Te(r, t) fields measured in the edge (r/a = 0.9–1.05) of TEXTOR L-mode plasmas are in close correlation with the local magnetic vacuum topology for low relative rotation frel = −0.2 kHz. In comparison with the 3D neutral and plasma transport code EMC3-Eirene, this provides substantial experimental evidence that for low relative rotation level and high resonant field amplitudes (normalized radial field strength ), a stochastic edge with a remnant island chain dominated by diffusive transport exists. Radially outside a helical scrape-off layer, the so-called laminar zone embedded into a stochastic domain is found to exist. In contrast for high relative rotation of frel = 1.8 kHz, the measured modulation of ne is shifted by π/2 toroidally with respect to the modelled vacuum topology. A pronounced flattening in Te(r) and a reduction in ne(r) is measured at the resonant flux surface and represents a clear signature for a magnetic island, which is phase shifted with respect to the vacuum island position. A correlated shift of the laminar zone radially outwards at the very plasma edge is observed suggesting that the actual near-field structure at the perturbation source is determined by the plasma response as well.
Extended MHD simulation of resonant magnetic perturbations