Multiline singularities applied to low-frequency scattering by a prolate spheroid

Building on the Rayleigh‐Stevenson approach fictitious internal source distributions responsible for the leading near‐field contribution of the long wavelength scattering by a non‐dissipative dielectric prolate spheroid are derived. The equivalent multiline sources arising from every polarization of the incoming field on the segment between the foci can be regarded as the result of an ultimate contraction of the volume polarization in the spheroid, or plainly as prolonged multipoles. In the low‐frequency asymptotic solution of the first‐order in terms of ω the solutions involve line and strip currents, and biline and quadriline charges, the density distributions of which obey simple polynomial laws. Numerical examples are provided, demonstrating their significance in the calculation of near‐zone fields in comparison with the direct radiation of elementary sets of point sources approximating the multiline distributions. The range of validity of the low‐frequency expansion is estimated by comparing with results obtained using the T‐matrix method.