Hybridization of the Method of Auxiliary Sources (MAS) with the Fast Multipole Method (FMM) for Scattering from Large Arrays of Cylinders

A hybridization of the Method of Auxiliary Sources (MAS) and the Fast Multipole Method (FMM) is developed and applied for the electromagnetic scattering problem by a large array of parallel circular cylinders. Such an array can serve as a model for the tree trunks of a forest or an orchard. As a starting point, a standard MAS formulation is used, where auxiliary sources are located on fictitious curves inside/outside the physical boundaries of the tree trunks. Next, by adopting an FMM setting, the far-field interactions are approximated as perturbations of a central interaction between the centroids of properly selected clusters encompassing neighboring sources and matching points. Numerical comparisons of efficiency and accuracy of the proposed hybridization are reported, together with discussions for the optimal selections of the involved parameters.