Linear mode conversion of forward and backward surface waves in axially non-uniform plasmas

It is shown that in axially non-uniform plasmas forward and backward surface waves convert into each other in the region of a complex turning point. In the absence of dissipation the coefficient of transformation reaches unity. The complex turning point is due to field asymmetry or surrounding dielectric walls or transverse (radial) density inhomogeneity. The calculations are performed for the case of antisymmetric surface waves propagating on a thin, axially non-uniform, plasma layer.