WAVE PROPAGATION IN A CYLINDRICAL WAVE GUIDE CONTAINING INHOMOGENEOUS PLASMA INVOLVING A TURNING POINT

Abstract

Propagation of axially symmetric E-type and H-type modes of electromagnetic waves in a radially inhomogeneous plasma inside a wave guide is considered. For E-type modes conditions for the propagation of slow surface waves along the plasma–dielectric interface have been obtained. Approximate expressions for fields for wavelengths much smaller than the ratio of the gradient of the permittivity to the permittivity of the plasma are also given.It is also shown that if the dielectric constant ε(r) of the plasma vanishes along a particular surface r = r₀, the electromagnetic fields for E-type modes behave singularly along this surface. In particular, if ε(r) has a simple zero at r₀ ≠ 0, the radial and the longitudinal electric fields become singular as 1/ε(r₀) and log ε(r₀) respectively at r₀. On the other hand, if ε(r) has a multiple zero at r₀, the singularities of the above-mentioned fields will be as strong as a multiple pole at r₀.Turning-point phenomena are also observed when the radial wave number [Formula: see text] vanishes along a surface. It is shown that the fields are oscillatory in the region [Formula: see text] and evanescent in the region [Formula: see text] for both E-type and H-type modes. The treatment of the singular behavior of the fields at ε(r) = 0, and of the turning-point phenomena at [Formula: see text], does not consider any boundary effect; therefore the results obtained here will be valid also for an inhomogeneous plasma column in free space.