Interaction between an electromagnetic wave and a bounded plasma

This paper treats reflection and absorption of an electromagnetic wave by a bounded plasma. Inevitably in considering spatial dispersion, the necessity arises to formulate an additional boundary condition. In macroscopic discussion such conditions must be postulated, but this cannot be regarded as satisfactory. The microscopic approach, using the kinetic equation method, transfers the center of gravity of the problem to the model of the boundary. But the ordinarily used formal conditions of the so-called "specular" or "diffuse" reflection of electrons of the medium from the surface do not permit elucidation of the physical conditions to which they correspond.The present article discusses the case of a magnetic field in one half of space only and discusses the impingement on a plasma of an electromagnetic wave polarized both along the stationary magnetic field and transverse to it.In the introduction the problem is formulated and boundary properties are determined. In the first part, in agreement with the boundary model, there is the unperturbed distribution function and a stationary magnetic field. It is assumed here that plasma pressure is small compared to magnetic pressure. The second part is devoted to finding the non-equilibrium addition to the distribution function caused by the impinging electromagnetic wave. The presence of regions with different properties leads to the fact that the condition of periodicity of the distribution function in azimuthal angle is insufficient for this problem. The third part studies the particular case of polarization of an impinging wave when the electric vector is parallel to the stationary magnetic field. In the region of frequencies that correspond to a weak space dispersion, general expressions have been written for the fields, and the reflection coefficient r and the absorption coefficient A = 1-|r|2 have been obtained. Within the limits of the conventional approximation, energy absorption does not depend on the magnetic field, and it coincides with Aspecs [2]. Finally, in the fourth part, the oblique impingement of an electric-vector wave that is perpendicular to the stationary magnetic field is studied. In this case energy losses arise that depend on the magnetic field and also losses due to the excitation of a longitudinal electromagnetic plasma wave.On the grounds of the study performed, one can conclude that with an increase of the magnetic field, the boundary, with respect to its reflecting and absorbing properties, approaches a mirror boundary. This enables one to talk of a universal boundary condition. This work indicates the limits of applicability of the universal con dition in different problems.