Surface Wave Echo in a Plasma Slab

Plasma echo theory is revisited, and we apply it to a plasma slab bounded by a vacuum. Spatial echoes in a slab plasma are investigated by calculating the electric field produced by external charges and satisfying the boundary conditions at the interfaces. We determine the echo spots associated with the symmetric mode of the surface wave in the slab. Naturally, in the course of development, the dispersion relation of the electrostatic surface plasma wave in a slab geometry is derived kinetically by satisfying the specular reflection boundary condition for the distribution function. We show that echoes can occur at various spots. The diversity of echo occurrence spots is due to the boundary terms, and appears to be owing to the reflections of the waves from the interface.