Modulational and Raman instabilities in the relativistic regime
- Centre de Physique Theorique (UPR 14 du CNRS), Ecole Polytechnique, 91128 Palaiseau Cedex (France)
- Centre de Developpement des Technologies Avancees, Haut Commissariat a la Recherche, BP 1017, Alger-Gare, and Universite des Sciences et de la Technologie Houari Boumediene, BP 32, El Alia, Bab ezzouar, Algiers (Algeria)
A large amplitude electromagnetic wave propagating in a plasma is known to be subject to severe modulational and Raman instabilities. Previous works were devoted to the weakly relativistic limit and applied mainly to a cold underdense plasma. One extends these works to include the fully relativistic limit for a circularly polarized light for which one derives the dispersion relation in a one-dimensional plasma. The characteristics of the instabilities are also calculated in the case where the plasma is classically overdense, with 1{lt}({omega}{sub {ital p}}/{omega}{sub 0}){sup 2}{lt}{gamma}, where {omega}{sub {ital p}} is the plasma frequency, {omega}{sub 0} is the laser frequency, and {gamma} is the relativistic factor of an electron in the laser field. Particle-in-cell simulations confirm the results of the numerical solutions of the dispersion relation. For ({omega}{sub {ital p}}/{omega}{sub 0}){sup 2}/{gamma}=0.57 the growth rate can be as large as 0.52{omega}{sub 0}. The nonlinear stage of the instability results in a strong heating of the electron distribution function. The theory is further extended to the case of an initially hot plasma, for which the dispersion relation of the instabilities is established. Its analytical solution is given in the case of a low density plasma. Particle-in-cell simulations are used to treat the general case. One observes a strong reduction of the growth rate of the instability, which tends to restore the possibility to propagate relativistic waves in plasmas. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
- OSTI ID:
- 165337
- Journal Information:
- Physics of Plasmas, Vol. 2, Issue 7; Other Information: PBD: Jul 1995
- Country of Publication:
- United States
- Language:
- English
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