Modeling of Perturbation Magnetic Field Based on Scrape-Off Layer Currents (SOLCs) During ELMs in DIII-D

The poloidal perturbation magnetic field (B$_{\delta B})$ measured by the Mirnov diagnostic at the peak of ELMs in H-mode discharges on the DIII-D tokamak exhibits idiosyncratic features in its poloidal variation: the field peaks in the divertor, and is larger (``anti-ballooning'') and opposite in sign on the inboard side in comparison with the outboard side. A model, developed for calculating B$_{\delta B}$ consistent with measured scrape-off layer current (SOLC), reproduces these idiosyncratic features. A narrow magnetic structure was also observed by the Mirnov diagnostic at the outboard mid-plane in some ELMs, which appeared to be qualitatively similar to filaments reported earlier in DIII-D [1] and NSTX [2]. The SOLC-based model also reproduces such a filament structure. [1] E.J. Strait, et al., Phys. Plasmas \textbf{4}, 1783 (1997). [2] R. Maingi, et al., Phys. Plasmas \textbf{13}, 092510 (2006).