Control of edge localized modes through toroidally asymmetric scrape-off layer current perturbations

Resonant magnetic perturbations (RMPs) can suppress the edge-localized MHD instabilities (ELMs) that limit the divertor target lifetime of H-mode tokamak fusion reactors. However, efficiently driving RMPs requires placing current carrying conductors as close as possible to the plasma, and engineering issues complicate the design of in-vessel components. We suggest driving the needed current through the scrape-off layer (SOL) plasma itself: current densities as large as J$_{sat}$=en$_{i}$c$_{s}$ can be driven by several means, including biasing the target to potentials of order T$_{e}$. Biasing in a toroidally varying fashion generates an asymmetric current density parallel to field lines in the SOL and a magnetic perturbation that is naturally aligned with field lines near the separatrix. Analytic estimates indicate that the resonant harmonics are larger than the $\delta $B/B $>$ 10$^{-4}$ criterion required for experimental ELM control. Magnetic island structure inside the separatrix will be investigated using the BOUT code.