Low-frequency electromagnetic scattering by two PEC spheres buried in conductive medium
Résumé
Analytical approaches of low-frequency electromagnetic scattering by perfectly conducting (PEC) bodies in conductive media involve expanding fields into positive integral powers of (jk), k wavenumber of the embedding medium at frequency ω, k = √jωσμ, σ conductivity, μ permeability, and calculating the real-valued vector coefficients at each power n: Rayleigh term n = 0, first dynamic ones n = 2, n = 3, the n = 1 term being trivial due to absence of primary field term for a magnetic dipole (current loop sources are employed, assimilated to dipoles). The magnetic field comprises an in-phase component (essentially from n = 0) and a quadrature component (from n = 2). In this contribution two simple bodies are modeled as spheres, of arbitrary radii and distance from one another (contact excepted), with limit case of one sphere collapsed to a plane, the magnetic dipole being of arbitrary location and orientation. The BVP is dealt with in the bispherical system of coordinates (attached to the spheres) and scalar/vector Laplace equations handled via harmonic eigenfunction expansions and using R-separability, + boundary conditions on the two surfaces. The main points of the analytical works carried out are sketched in the provided documents while numerical results obtained at low computational cost, even if the spheres almost touch one another, illustrate the investigation.