SURFACE CURRENT EXCITATION ON AN INHOMOGENEOUSLY SHEATHED PLASMA-IMMERSED CYLINDER BY ELECTROMAGNETIC AND ELECTROKINETIC WAVES

Abstract

A theoretical investigation is described which analyzes the effect of an inhomogeneous sheath on the surface currents and scattering cross section of an infinitely long, perfectly conducting, circular cylinder immersed in an isotropic collisionless, compressible plasma by plane electromagnetic (EM) and electrokinetic (EK) waves incident at an arbitrary angle with respect to the cylinder axis. The linearized fluid equations are used in the analysis, with the inhomogeneous sheath taken to extend a finite distance into the plasma from the cylinder surface, on the order of 10 electron Debye lengths, beyond which the plasma is uniform. The numerical results for the surface currents obtained from the inhomogeneous sheath analysis are compared with those obtained when the sheath is replaced by a free-space region, called the vacuum sheath. It is found that for EM wave incidence, the surface currents are practically independent of the sheath and the finite plasma temperature. For EK wave incidence, the sheath has an attenuating effect on the currents produced, compared with the sheathless case, with the attenuating effect of the vacuum sheath being greater than that of the inhomogeneous sheath. The scattering cross sections for EM wave incidence are, for the scattered fields with the same polarization as the incident wave, also independent of the sheath and finite plasma temperature. The scattered fields with polarization different from that of the incident wave have cross sections generally less than 10−2 of the scattered fields with the incident wave polarization.