S. V. Vladimirov

Ion-acoustic solitons in electron--positron--ion plasmas

The ion‐acoustic solitons are investigated in three‐component plasmas, whose constituents are electrons, positrons, and singly charged ions. It is found that the presence of the positron component in such a multispecies plasma can result in reduction of the ion‐acoustic soliton amplitudes.

Recent advances in the theory of nonlinear surface waves

Abstract Recent advances associated with an improvement of the popular cold-plasma sharp-boundary model in the theory of nonlinear surface waves in low-temperature plasmas are reviewed. The revised boundary model calls for the existence of induced nonlinear surface charges and currents in an infinitely thin (spatially singular) layer at the plasma boundary. It provides a much more accurate description of the physics of the region, especially with respect to the nonlinear effects. Various nonlinear wave phenomena of current interest, such as those of the third-order ponderomotive effect, nonlinear waves, and soliton formation, are discussed. It is demonstrated that for the problems considered, the results from the new model agree well with those obtained from the kinetic theory. The latter inherently includes a more complete description of the boundary conditions since the plasma density can vanish smoothly (and physically consistently) within a boundary layer adjacent to the wall. The layer, or sheath region, has a small but finite dimension usually of the order of the Debye length. Effectively, the new model takes into account the relevant physical processes occuring in this layer, which itself is nevertheless taken to be of zero width. Thus, spatially singular charges and currents appear in the model. Furthermore, a new class of nonlinear cold-plasma surface wave solutions is also reviewed. These solutions are obtained by separating the temporal and spatial dependences of the physical quantities. They are mathematically exact in the sense that starting from the basic cold-plasma equations and boundary conditions, no approximation of any kind needs to be made in obtaining them. Exact nonlinear surface wave solutions in cylindrically and spherically bounded plasmas, as well as the effects of constant and oscillatory external electric fields in the dielectric container, are presented. Modern applications of the results from the above topics in various branches of physics, chemistry, and technology are discussed.

On the physics of the plasma maser

Abstract We consider the plasma-maser interactions of electrostatic waves for both magnetized and unmagnetized plasmas. The difference between these two cases is clarified. A correct transition to the zero magnetic field is presented. The accuracy of the conservation of the adiabatic invariant (the number of quanta of the nonresonant waves) is calculated.

Boundary effects on the nonlinear interactions of surface waves

A traditional cold‐plasma boundary model is revised to allow for proper description of nonlinear effects in surface wave propagation. It is shown that induced nonlinear surface currents can exist at the boundary. As an example, the third‐order ponderomotive phenomena are considered, and the effect of the boundary condition on these nonlinear interactions is examined.

Surface wave solitons in an electronic medium

Abstract Nonlinear surface waves at the boundary of an electronic medium are investigated. It is found that when the surface currents are taken into account, a new type of solitons can propagate along the interface. The solitons travel with speeds faster than that of light in the bounding dielectric but to the order considered emit no radiation.

Solitary ionizing surface waves on low-temperature plasmas

A simple model for studying finite-amplitude ionizing nonlinear surface waves propagating in a partially ionized low-temperature plasma, in which collisional effects such as ionization, recombination, and friction are dominant, is proposed. The authors consider the lowest order namely, second order in the fields) nonlinear problem and investigate the evolution of finite-amplitude electromagnetic surface waves. It is shown that the waves are governed by a modified Korteweg-de Vries (KdV) equation and that new types of solitary waves can exist. The structures of the latter are mathematically similar to, but physically quite different from, that of the KdV soliton. >

Growth rates for modulational instabilities of radio waves in highly collisional ionospheric plasmas

Accounting for ponderomotive force and differential Joule heating nonlinearities as well as relativistic electron mass variation, we consider the parametric coupling between a large- amplitude electromagnetic wave and nonresonant density and temperature perturbations. A nonlinear dispersion relation that is appropriate for the modulational instability is presented. Some interesting regimes for the thermal modulational instability are identified, and expressions for their increments are obtained. The results can be useful in understanding the phenomena of enhanced density and temperature fluctuations that have been observed during the artificial modification of the Earths ionosphere by high-power radio waves.

Plasma-maser effect and evolution of resonant waves in turbulent plasmas

The evolution of resonant waves due to the nonlinear interaction associated with the plasma-maser effect is considered, and the nonlinear growth rate obtained. It is shown that the latter contains a polarization (only for the resonant waves) as well as a direct third-order contribution. In particular, the effect of the plasma-maser mechanism on the beam instability caused by Landau growth is investigated. It is shown that this effect can significantly modify the behavior of the instability. The conditions for the dominance of the plasma-maser effect nonlinearity over that of the usual quasilinear mechanism are given.

Attenuation of the surface wave fields into a degenerate plasma: another Kohn anomaly

It is demonstrated that due to the Kohn singularity the attenuation of surface waves into the bulk of a semi-infinite degenerate plasma can follow a power-law (no exponential decrease, as in a classical plasma). This effect is analogous to the power-law decrease of the field of a test charge in a degenerate plasma.

Modulational instability of Langmuir waves in dense plasmas

The modulational instability development of Langmuir waves is investigated in highly collisional plasmas where the characteristic frequency Ω of the modulated perturbations is much less than νeff, the effective electron collision frequency. It is demonstrated that the modulational instability for the situation considered is mostly determined by collisional effects (differential Joule heating nonlinearity), in contrast to the well‐known modulational instability in collisionless plasmas (where ponderomotive force nonlinearity dominates). Rates and thresholds of the instability are found in various limits. The modulational instability is most effective when the angles between a pump wave vector and wave vectors of the modulational perturbations are of order unity.