Magnetic-perturbation-induced plasma transport in H-mode pedestals

Plasma toroidal rotation can prevent reconnection of externally applied resonant magnetic perturbation (RMP) fields on rational surfaces and hence magnetic island formation and stochasticity in the edge of tokamak H-mode plasmas. However, magnetic flutter induced by RMPs off the rational surfaces causes a radial electron heat diffusivity $\chi_e^{RMP}\sim (\delta B_r/B_0)^2\chi_\| F(x)$ in which $\chi_\|\sim v_{Te}^2/\nu_e$ is an effective parallel electron heat diffusivity and $F$ is a spatially varying factor [1]. The flutter also diffuses electrons radially and causes a factor of about 3 smaller increases in density diffusion. Since the electron density transport is non-ambipolar, this flutter process also modifies the radial electric field and plasma toroidal rotation. This work extends the previously developed periodic cylinder screw pinch model [1] of RMP-flutter-induced plasma transport to a full toroidal model which is axisymmetric to lowest order plus gyroradius-small magnetic field perturbations. The possible role of the RMP-flutter-induced plasma transport in reducing pressure gradients in H-mode pedestals and thereby suppressing ELMs will be discussed.\\[4pt] [1] J.D.\ Callen et al., UW-CPTC 11-13, http://www.cptc.wisc.edu (submitted to Nucl.\ Fusion.)