Particle acceleration by a non-linear langmuir wave in an inhomogeneous plasma

An expression for the average particle distribution function disturbed by a non-linear Langmuir wave in an inhomogeneous plasma is derived. Particle acceleration due to the resonant wave-particle interaction is investigated.     

Polarization of weakly nonlinear magnetoacoustic wave in inhomogeneous plasma

The relationships between the components of a nonlinear magnetoacoustic wave near and far from a caustic are investigated.St. Petersburg State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 11, pp. 1365–1372, November, 1994.     

Nonlinear modulation of a powerful electromagnetic wave in a weakly inhomogeneous plasma

We show the possibility for nonlinear trapping of a Langmuir wave in the region of weak inhomogeneity of plasma under parametric interaction with a powerful electromagnetic wave. Under overcritical conditions in the presence of dissipation and imperfect reflection, space-time amplitude correlations emerge and wave soliton structures are then formed. Powerful regular oscillations appear in the system, leading to a giant modulation of the pump pulse. The Langmuir nonlinearity contribution increases with the above-threshold value, which results in a sharp increase and compression of solitary waves.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 9, pp. 1096–1102, September, 1996.     

Nonlinear wave damping on an electron hole in a weakly inhomogeneous plasma

Nonlinear damping of the Langmuir wave in a weakly inhomogeneous plasma with a negative concentration gradient is considered. For phase velocities close to the thermal velocity of electrons, their dispersion strongly differs from the linear one and cannot be taken into account by means of a small correction to the linear dispersion law. Based on the energy balance and nonlinear dispersion equations, a dependence of the wave amplitude on its phase velocity is established together with the limiting phase velocity at which the wave is completely damped.     

Evolution of a quasi-neutral shock wave in inhomogeneous semiconductors

It is shown that in a current carrying extrinsic semiconductor, a quasi-neutral wave of carrier concentrations evolves into a shock wave(s). Inhomogeneous distribution of impurities causes either amplification (an absolute instability) or depression of these waves.     

Generation of a magnetic field in a weakly inhomogeneous plasma interacting with a short laser pulse

The generation of a quasistationary magnetic field in a plasma interacting with a weakly focused low-intensity short laser pulse has been studied. It has been shown that the magnetic field changes direction at times comparable with the free path time of effective electrons. Generation also occurs after the switching off of the short pulse and the maximum field is proportional to the duration of the pulse and is reached at times larger than the free path time of the suprathermal electrons.     

Increase of the backward Raman reflectivity caused by the langmuir decay instability in an inhomogeneous plasma: the loss of gradient stabilization

We investigate the nonlinear evolution of the backward stimulated Raman scattering (BSRS) in the regime where the nonlinear saturation mechanism is the Langmuir decay instability resulting from the coupling of the BSRS-generated Langmuir wave with the ion acoustic waves. We present numerical results obtained with a fluid-type code in one- and two-dimensional spatial dimensions, in the case of an inhomogeneous plasma. The plasma density is under quarter-critical and depends linearly on the longitudinal spatial coordinate, in the regime where the Rosenbluth gain factor for the amplitude, denoted as G(Ros), is in the range pi/2< or =G_(Ros)< or =6. We observe that the Langmuir decay instability is able to suppress the gradient stabilization and restore the absolute nature of BSRS, thus leading to a significantly increased BSRS reflectivity.     

High-frequency wave packets in inhomogeneous plasma with striction nonlinearity

The study of the evolution of 1 —D intense high-frequency (HF) packets in a smoothly inhomogeneous plane-layer medium with local and nonlocal striction nonlinearities is reviewed. The role of low-frequency (LF) radiation from an HF packet in an inhomogeneous medium with nonlocal nonlinearity is discussed.Published from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 1, pp. 80–92, January, 1996.This work was supported by the International Science Foundation and the Ministry for Science of Russia (Grant No R8V300).     

Penetration of an ordinary wave into a weakly inhomogeneous magnetoplasma at oblique incidence

A theory is given describing the propagation of high-frequency electromagnetic waves in a plane-stratified weakly inhomogeneous plasma. The density gradient is supposed to be perpendicular to the external magnetic field and the wave vector is expected not to be generally parallel to the plane given by both the preceding vectors. The analysis points out that the ordinary wave can penetrate through the plasma resonance region if the direction of vacuum wave vector is chosen appropriately. Analytical expressions for the reflecion and transmission coefficients are obtained and their dependence on the direction cosines of the wave vector of the incident is studied. The paper further shows in outline that, after transmission through the plasma resonance, the ordinary wave is transformed into an extraordinary wave and the latter is reflected back to the region of the hybrid resonance. In this region the extraordinary wave is fully transformed into the Bernstein modes.     

Low-frequency instability of an inhomogeneous weakly ionized plasma in crossed electric and inhomogeneous magnetic fields

The paper discusses the drift dissipative instability that arises in a weakly ionized inhomogeneous plasma in crossed electric and magnetic fields. The potential perturbations are studied in the WKB (Wentzel-Krammers-Brillouin) approximation, i.e. for k = d lnn ₀/dx. The critical magnetic field, beyond the value of which the plasma is again stable against the studied perturbations, is computed. The effect of the inhomogeneity of the magnetic field modelled by a gravitational field is analyzed and the effect of a magnetic field, growing in the direction opposite to that of the plasma density, is pointed out. Under certain circumstances similar phenomena also arise in the current-convective instability.The author wishes to express his thanks to J. Václavík, K. Jungwirth and J. Preinhaelter for their stimulating discussions and comments.     

不均匀等离子体中电磁波与Langmuir波的相互作用

通过理论研究与数值计算,不均匀等离子体中Langmuir波与电磁波的相互作用及其线性模式转换规律得到了充分的展示.导出了不均匀等离子体中的电磁色散关系,研究了入射电磁波或Langmuir波在通过不均匀等离子体的过程中发生转换的物理过程,以及波的传播矢量随空间坐标变化的关系,并对电磁波与Langmuir波相互作用的机理进行了讨论.研究结果对密度梯度所驱动的等离子体波产生电磁辐射的研究具有重要意义. 关键词： 电磁波 Langmuir波 不均匀等离子体 线性模式转换     

Wave propagation in a weakly inhomogeneous medium

We develop an asymptotic method to describe the n-dimensional wave propagation through nonlinear inhomogeneous media characterized by dissipative and (or) dispersive systems of partial differential equations. This method is used to study the bidimensional propagation of surface water waves of varying depth.     

Ion-acoustic wave evolution in an inhomogeneous flowing plasma

The excitation of ion-acoustic waves with a grid immersed in an inhomogeneous flowing plasma was studied experimentally. Consideration of the effects of the ion flow was examined. The experiments indicated that there were two features of distinct interest. First, there could be a significant difference in the received signals if the wave was launched along or against the direction of the plasma flow. Second, the dominant “propagating response” whose waveform resembled the time derivative of the applied voltage signal was excited at low excitation frequencies.     

Ion acoustic solitary wave in an inhomogeneous plasma with non-uniform temperature

A modifiedK-dV equation, which describes the propagation of an ion acoustic solitary wave in an inhomogeneous plasma with both density and temperature gradients, is derived. It is shown that, the velocity of a solitary wave increases as it propagates towards regions of increasing temperature.     

Modulational instability of a weakly relativistic ion acoustic wave in a warm plasma with nonthermal electrons

An investigation has been made of modulational instability of a nonlinear ion acoustic wave in a weakly relativistic warm unmagnetized nonthermal plasma whose constituents are an inertial ion fluid and nonthermally distributed electrons. Up to the second order of the perturbation theory, a nonlinear Schr?dinger type (NST) equation for the complex amplitude of the perturbed ion density is obtained. The coefficients of this equation show that the relativistic effect, the finite ion temperature and the nonthermal electrons modify the condition of the modulational stability. The association between the small-wavenumber limit of the NST equation and the oscillatory solution of the Korteweg－de Varies equation, obtained by a reductive perturbation theory, is satisfied.