N. L. Tsintsadze

Relativistic nonlinear effects in plasmas

Abstract The purpose of this article is to present a review of the nonlinear effects associated with relativistic electron-mass variation and the ponderomotive force in unmagnetized as well as magnetized plasmas. Many high-frequency waves can become unstable with respect to the electron-mass modulation and the excitation of low-frequency density fluctuations. The nonlinear equations which govern the evolution of the modulationally unstable waves are derived. The phenomena of soliton formation, radiation collapse, and profile modification are investigated. Finite amplitude theories of the envelope solitons are reviewed. In a multidimensional situation, the electromagnetic waves can undergo self-focusing. The use of the variational methods allows one to calculate the nonlinear wavenumber and radius of the self-focused laser beams. Analytical solutions for the self-trapped radiation and the three-dimensional relativistic solitons are obtained. It is found that magnetized plasmas can support the propagation of new types of ultrarelativistic electromagnetic waves. The modulational instability of the latter is analyzed. Furthermore, it is shown that the relativistic ponderomotive force in a magnetized plasma can produce large amplitude field-aligned electrostatic potentials which can effectively accelerate particles to very high energies. Finally, we consider the nonlinear propagation of intense electromagnetic waves in electron-positron plasmas. Possible applications in inertial fusion, beat-wave particle accelerator, rf heating of magnetically confined plasmas, and pulsar radiation are pointed out.

Intense solitary laser pulse propagation in a plasma

Previous work [Yu, Shukla, and Tsintsadze, Phys. Fluids 25, 1049 (1982)] on intense laser pulse propagation in plasmas is generalized to include nonlinear ion motion which can be of importance in the slow plasma response.

Linear and nonlinear dust lattice waves in plasma crystals

Abstract Linear and nonlinear studies of dust lattice waves in a dusty plasma crystal have been carried out on the basis of the Schrodinger equation which is deduced from Poissons equation for small dust grain potentials. The spatial distribution of the potential in the dust-lattice includes the effect of the whole system of the dust particles. Such a self-consistent analysis gives a dispersion relation for the dust lattice wave, which is different from the expression found earlier. The frequency of the lattice oscillation increases considerably for large grain charges. Furthermore, it is found that an ideal lattice can only exist if the dusty plasma parameters satisfy a definite relationship between the dusty plasma Debye radius, the inter-grain separation, and the grain size. Finally, accounting for the weak nonlinearities, we also derive a Korteweg-de Vries (KdV) equation for the nonlinear dust lattice waves in the long wavelength approximation (kd≪1), where k is the wave number and d the inter-grain spacing.

Nonlinear interaction of a powerful laser with an electron plasma

Interaction of a high‐power circularly polarized electromagnetic wave with forced Langmuir oscillations is shown to result in solitary wave structure whose electron density profile has a depression at the center and humps on the sides.

Nonlinear interaction of photons and phonons in a relativistically hot electron-positron gas

Nonlinear interaction between intense photons and sound waves in a relativistically hot electron–positron plasma is considered. The modulational instability of a constant amplitude photon is investigated and the formation of polarons (localized photon envelopes trapped in a self‐created density cavity) is discussed. The relevance of this investigation to astrophysical plasmas is pointed out.

Solitary acoustic waves in weakly ionized gases

Abstract We show that acoustic waves in a weakly ionized collisional plasma in the one-dimensional case are governed by a Kortewegde Vries equation. Solitary sound wave solutions can thus be found.

Dust lattice waves in a plasma crystal

The dust lattice wave in dusty plasma crystals is reexamined, taking into account the dependence of the dust grain charge on the grain potential. The Poisson equation for small grain potentials then assumes the form of the Schrodinger equation. The spatial distribution of the potential in the lattice includes the effect of the whole system of dust particles. Such a self-consistent description gives the dispersion relation for the dust lattice wave, which is different from the expression found earlier. The case of large grain charge is also considered. The frequency of the lattice oscillation increases considerably for large grain charges. Furthermore, it is noted that an ideal lattice can only exist if the dusty plasma parameters satisfy a definite relation between the dusty plasma Debye radius, the intergrain separation, and the grain size.

Electromagnetic solitons in degenerate relativistic electron–positron plasma

The existence of soliton-like electromagnetic (EM) distributions in a fully degenerate electron–positron plasma is studied applying relativistic hydrodynamic and Maxwell equations. For a circularly polarized wave it is found that the soliton solutions exist both in relativistic as well as nonrelativistic degenerate plasmas. Plasma density in the region of soliton pulse localization is reduced considerably. The possibility of plasma cavitation is also shown.

Fluid-maxwell simulation of laser pulse dynamics in overdense plasma

A one-dimensional model of collisionless electron plasma, described by the full system of Maxwell and relativistic hydrodynamic equations, is exploited to study the interaction of relativistic, strong, circularly polarized laser pulses with an overdense plasma. Numerical simulations for the ultrarelativistic pulses demonstrates that for the low as well as for the high background density, the major part of the penetrated energy remains trapped for a long time in a nonstationary layer near the plasma front end; only a minor portion resides in solitons. Important details of the interaction for the moderately intense and strongly relativistic pulses for semi-infinite and thin plasma layers are revealed. An interesting additional consequence of the long-time confinement of relativistic strong radiation in an overdense plasma is analyzed. It is shown that intensive pair production by the driven motion of plasma electrons takes place due to the trident process.

Modulational instabilities due to relativistic electron mass variations

Abstract A generalized dispersion relation, which describes modulational instabilities in a pumped electron-ion plasma, is investigated, and it is shown that relativistic electron mass variations can be important, even when comparatively small amplitude waves are considered. We also demonstrate the existence of new unstable solutions.