Resonant absorption in a plasma step profile

Abstract

Resonant absorption of p-polarized light shone on a plane-layered plasma with a step profile, is discussed as a function of wavelength (or critical density nc) of the light; for simplicity the incidence angle is assumed small. If nc lies within or above the step, the absorption A is given by Ginzburg's result (1970) modified by strong reflections at the foot and top of the step. The absorption above is total for particular values of nc and theta . For nc crossing the top of the density step the absorption is not monotonical; it exhibits a minimum that vanishes for zero radius of curvature sigma there (A approximately mod ln sigma mod 2), and zero collision frequency nu (A approximately mod 1n nu mod -2). The results are applied to the profile produced by irradiating a solid target with a high-intensity pulse that steepens the plasma by radiation pressure.