Stabilization of resistive wall modes by slow plasma rotation

External kinks that drive magnetic islands inside a plasma can be stabilized by a resistive wall for even a slow plasma rotation. It is shown that only a subclass of ideal kinks avoid driving islands and stabilization by slow rotation. In addition, the separatrix of a tokamak divertor causes external kink instabilities to have resonant surfaces within the plasma and drive islands. Consequently, tokamaks with a hot divertor scrape-off layer may be more stable to resistive wall modes than tokamaks with limiters. It is shown that the calculation and description of the stability of wall modes is greatly simplified by the use of the inductance, resistance, and torque associated with a surface current.