Role of singular layers in the plasma response to resonant magnetic perturbations

Abstract

Abstract. The response of an H-mode plasma to magnetic perturbations that are resonant in the edge is evaluated using a fluid model. With two exceptions, the plasma rotation suppresses the formation of magnetic islands, holding their widths to less than a tenth of those predicted by the vacuum approximation. The two exceptions are at the foot of the pedestal, where the plasma becomes more resistive, and at the surface where the perpendicular component of the electron velocity reverses. The perturbations exert a force on the plasma that is such as to brake the perpendicular component of the electron rotation. In the pedestal, the corresponding Maxwell stress drives the radial electric field in such a way as to accelerate ion rotation. Despite the suppression of the islands, the perturbations give rise to particle fluxes caused by magnetic flutter, with a negligible contribution from E×B convection. In the pedestal, the fluxes are such as to reduce the density.

Non-linear magnetohydrodynamic modeling of plasma response to resonant magnetic perturbations

“…The screening factor is much larger here than in the cylindrical modeling where the resonant component was reduced under 1% [12]. Comparatively, other simulations made with toroidal codes [13,14] also found a similar screening factor (∼ 10 − 20%), which is 1 − 2 orders of magnitude larger than the results in cylindrical approximation [11,12,28] and in the analytical calculations from layer theory [29]. The discrepancy between modeling in realistic geometry and simpler models is not yet understood.…”

Enhanced particle transport caused by resonant magnetic perturbations in the J-TEXT tokamak

“…Taking into account the plasma response to the externally applied RMPs, the RMP amplitude inside the plasma could be considerably reduced compared to that obtained with the vacuum approximation. The screening current induced by plasma flow [15][16][17][18][19][20][21][22] and the rotation braking indicate the plasma response to applied RMPs [3,9,[23][24][25][26].…”

Understanding the effect of resonant magnetic perturbations on tearing mode dynamics

“…6 To explain the changed TM dynamics caused by applied RMPs, many theoretical and numerical studies related to RMPs have been carried out. 2,[19][20][21][22][23][24][25][26][27][28][29][30][31][32] Some authors supposed that RMPs changed ∆' so as to stabilize tearing instability. 19 However, only the active RMPs experiment could be explained in which RMPs had a constant phase with respect to the a) Author to whom correspondence should be addressed.…”