Electromagnetic field in the source region: A review

A review of recent developments in the delineation of the electromagnetic field in the source region of a general, linear, homogeneous bianisotropic medium is presented. Thereby, a field representation, initially developed by Fikioris for isotropic mediums, is generalized and shown to be a proper way of representing the complete field structure. In particular, the field representation permits a concise extraction of the field singularity. It is further emphasized that the complete field representation requires the knowledge of the infinite-medium dyadic Green function which is only available for special classes of (but not the most general) linear, homogeneous bianisotropic mediums. The specific roles of the Poisson dyadic and the depolarization dyadic are illuminated and their importance to approximative field representations is underlined. Finally, the significance of the field in the source region to a theoretical understanding of electromagnetic field structure in general as well as to its input into homogenization theories of particulate composites is discussed.