Electromagnetic Scattering by Finite Dense Plasmas

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Abstract
The often used hypothesis that a large overdense plasma medium may be treated as a perfect reflector is critically examined using a large homogeneous plasma sphere for particular emphasis as a simple scattering volume. This hypothesis is found to be in substantial error for densities between about four and κa/2 times the critical density where κ is the vacuum propagation constant of the incident field and a is the radius of the scatterer. The ``anomalous'' scattering in this restricted density range arises because of interference effects between the backscattered wave and tightly bound surface waves. These surface waves are of considerable importance for even very large (κa∼700) scatterers. The effects of absorption and inhomogeneity are also discussed. In general, it appears that deductions based on radar and other backscatter measurements are of questionable validity for a rather broad range of ionized scattering media.