A direct look at creeping waves

To the human eye light rays appear as entities emanating from well defined bright regions on a scattering body. It is argued that these regions, whether associated with specular reflection, edge diffraction, or creeping waves (appearing as bright boundaries on curved bodies), can each be observed and studied independently using the filtering functions inherent in vision. The author discusses processing of a similar kind, emulated computationally, by simple windowing, of computed radiation. Sample data are shown that were obtained by applying to the outgoing axial field component a fourth-order Blackman-Harris window that is centered 90 degrees behind the observer and extends over 180 degrees . The magnitude (in terms of a scattering width) of the windowed radiation from an impedance cylinder is graphed for various impedance levels. Remapping these results provides the decay and launching constants for the dominant creeping wave modes.<>