Analysis of high resolution 2-D images of the m/n=2/1 tearing mode in KSTAR RMP experiments

In the 2011 KSTAR campaign, the m/n=2/1 tearing mode has often been observed in plasmas with externally applied static n=1 Resonant Magnetic Perturbation (RMP) fields. It is generally believed that the RMP can induce tearing of flux surfaces via the so-called mode penetration mechanism [1]: (1) the RMP slows the plasma rotation down to the resonance condition, (2) the plasma shielding current is minimized, and (3) the RMP fields penetrate into the plasma, tearing the flux surfaces. This scenario of tearing mode generation induced by RMP is consistent with the observed changes of the toroidal velocity profile and the appearance of tearing mode structures as reconstructed from 2-D electron cyclotron emission (ECE) images. In addition, the detailed 2-D ECE images of the tearing mode enabled a straightforward estimation of the delta prime, which is a critical parameter for understanding the tearing physics.\\[4pt] [1] F.L. Waelbroeck, \textit{Nucl. Fusion} \textbf{49} (2009).