Penetration of resonant magnetic perturbations in turbulent edge plasmas

Comprehension of the interactions between tokamak edge plasmas and externally induced resonant magnetic perturbations (RMPs) is an important step in the understanding of the control of edge-localized modes by these RMPs. Such control has been demonstrated experimentally, but previous theoretical investigations have revealed a possible screening of RMPs by a sheared rotation of the plasma. In this work, the penetration of RMPs is investigated via numerical simulations in a reduced magnetohydrodynamic model using the three-dimensional electromagnetic turbulence code EMEDGE3D. In this model, the plasma response to RMPs can be studied in the presence of flux-driven micro-turbulence and a transport barrier induced by sheared plasma rotation. The interplay is, in a first part, studied in a non-turbulent case to deduce a criterion for the penetration in a rotating plasma that is governed by the generation of counter currents. When the plasma is studied in a statistically stationary turbulent state, the self-consistent plasma rotation, governed by Reynolds and Maxwell stresses, leads to a self-organization where RMP penetrates. In a turbulent plasma in the presence of a transport barrier, the RMP harmonic that is resonant at the barrier centre is found to penetrate partially. This partial penetration is sufficient to trigger a local flattening of the pressure gradient that is known to be at the origin of the control of transport barrier relaxations in the present model.