Oblique Langmuir solitons and their self-compression in the ''free-flight'' regime
For the first time we have observed experimentally in a magnetized collisionless plasma, of the ''beam afterglow'', slow (approximately fixed relative to the plasma) oblique Langmuir solitons with an HF carrier on the branch of waves with the linear dispersion ..omega..=..omega../sub p/cosTHETA, which occur as a consequence of the modulational instability of the nonlinear waves. The longitudinal size of the solitons is less than the initial (beam) wavelength and it is impossible to call them envelope solitons. We show that after a time equal to their ''free-flight'' (along with the plasma) along the magnetic field: after the ''pump beam'' was switched off: the solitons experience appreciable self-compression. The solitons observed differ in priniciple from the well known, fast, soliton (H. Ikezi, P. J. Barrett, R. B. White, and A. Y. Wong, Phys. Fluids 14, 1997 (1971); S. M. Krivoruchko, Ya. B. Fainberg, V. D. Shapiro, and V. I. Shevchenko, Sov. Phys. JETP 40, 1039 (1975); V. D. Fedorchenko, Yu. P. Mazalov, A. S. Bakai, A. V. Pashchenko, and B. N. Rutkevich, JETP Lett. 18, 281 (1973)), which exists on the same branch of waves: the fast soliton moves several orders of magnitude faster, constitutes a potential hump without an HF carrier and arises as the result of another mechanism, such as a Korteweg--de Vries ion-sound or shallow-water soliton (H. Ikezi, R. P. H. Chang, and R. A. Stern, Phys. Rev. Lett. 36, 1047 (1976); B. B. Kadomtsev, Collective Phenomena in a Plasma, Nauka, Moscow, 1976, Ch. 3, section3; Ch. 5, section5 (English translation published by Pergamon Press)). The observed solitons with oscillation frequencies ..omega..1/3 to 1/2(omega)=/sub p/ are as yet not described in the theory.
- Research Organization:
- I. V. Kurchatov Institute of Atomic Energy
- OSTI ID:
- 6701228
- Journal Information:
- Sov. Phys. - JETP (Engl. Transl.); (United States), Vol. 51:5
- Country of Publication:
- United States
- Language:
- English
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