  General formula describing both the divertor strike point splitting and width
of magnetic islands created by resonant magnetic perturbations (RMPs) in a
poloidally diverted tokamak equilibrium is derived. Under the assumption that
the RMP is produced by coils at the low-field side such as those used to
control edge localized modes (ELMs) it is demonstrated that the width of
islands on different magnetic surfaces at the edge and the amount of divertor
splitting are related to each other. Explanation is provided of aligned maxima
of the perturbation spectra with the safety factor profile - an effect
empirically observed in models of many perturbation coil designs.
