SCATTERING FROM A CYLINDER COATED WITH AN INHOMOGENEOUS DIELECTRIC SHEATH

Abstract

As a space vehicle re-enters the atmosphere, a plasma sheath, surrounding the vehicle, is generated. It is well known that the sheath is inhomogeneous. However, to make this problem suitable for theoretical analysis, most investigators make the assumption that the sheath is homogeneous. To investigate the validity of this assumption, the idealized problem of the scattering of plane waves by a conducting cylinder coated with a stratified dielectric sheath is considered. The wave equation is separated using the vector wave-function method of Hansen and Stratton. It is then applied to the plane-wave scattering problem. The backscattering cross section is defined and obtained. Analytical expressions for the scattering coefficients of a thin inhomogeneous sheath are also given. Numerical computations are carried out for a specific variation of the dielectric sheath: i.e., ε(r) = ε0α/k0r, where α is a constant, k02 = ε2 με0, and ε0 is the free-space dielectric constant. Results are compared with the homogeneous sheath problem; the dielectric constant of the homogeneous sheath is taken to be the average value of that for the inhomogeneous sheath. It is found that in general rather distinct differences are observed except when the sheath is very thin.