Collisionless Absorption and Emission of Electromagnetic Waves by a Bounded Plasma

Résumé du livre

The absorption and emission of electromagnetic waves by a hot bounded plasma can be greatly influenced by the collective behavior of the plasma. A homogeneous slab model of a hot plasma is used in a theoretical study of these collective effects. A boundary-value problem is solved to find the fields in the plasma when a plane wave is incident on the plasma boundary. Power is found to be absorbed from the incident wave because of the Landau damping of longitudinal plasma waves excited in the plasma. If the incident wave frequency is close to one of the plasma wave resonance frequencies, the absorption may be substantial, but only if the Landau damping rate is approximately equal to the radiation damping rate, i.e., if the plasma is 'matched' to the radiation field. The width of an absorption line is the sum of the Landau damping and radiation damping widths. Electromagnetic noise radiation is emitted from a collisionless plasma because of the coupling of the field fluctuations in the plasma to the external radiation field at the plasma boundary. Plasma wave fluctuations are excited by fast electrons in the plasma and are reinforced by the collective response of the plasma at the resonance frequencies. Emission and absorption are related by Kirchhoff's law for a thermal plasma. For a nonthermal plasma the emission may be enhanced if there are many electrons in a high-energy tail of the distribution function. (Author).