On the Dipole Resonant Mode of an Ionized Gas Column

Abstract

In a recent paper, Makinson and Slade (1954) examined theoretically the scattering of a transverse-electric radio wave by an ionized gas column. In their treatment, a smooth radial distribution of ion density was replaced by a stepped approximation and the quasi-static equations (Kaiser and Closs 1952) were used to consider scattering by this stepped column. They claim that there exists a multiplicity of resonant dipole modes for a small cylindrical column in which the radial distribution of ionization is described by a Gaussian function. Previously, Kaiser and Closs (1952) had found a single, broad resonance peak by an approximate numerical solution of the quasi-static equations, using the Gaussian distribution itself. The purpose of this note is to suggest that the multiple resonances found by Makinson and Slade were created by the discontinuities in their approximation to the Gaussian function, and that the actual Gaussian distribution exhibits only one resonance.