Hose instability of relativistically strong femtosecond laser pulses with few field oscillations in a plasma under the excitation of a plasma wake wave

A detailed theoretical analysis is carried out of the hose instability of relativistically strong laser pulses propagating in a plasma, whose duration is less than the period of a plasma wake wave. An analytic expression is obtained for the displacement of the mass center of a wave pulse, and the effect of this instability on the modification of the spectrum of laser radiation is analyzed for a wide range of initial parameters. It is shown that the development of instability is characterized by a power-law (rather than exponential) time dependence along the propagation path and does not deteriorate the self-compression of laser pulses.     

Parametric excitation of Langmuir oscillations in a relativistic electron plasma

A systematic discussion is carried out of the parametric action of an external high-frequency field on a high-temperature plasma. The conditions for the onset of parametric resonance and the corresponding increments, as well as the frequency shift of the Langmuir oscillations under the action of a high-frequency field, are found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 58–61, May, 1982.     

Heating by an electron Bernstein wave in a spherical tokamak plasma via mode conversion

The first successful high power heating of a high dielectric constant spherical tokamak plasma by an electron Bernstein wave (EBW) is reported. An EBW was excited by mode conversion (MC) of an mode cyclotron wave injected from the low magnetic field side of the TST-2 spherical tokamak. Evidence of electron heating was observed as increases in the stored energy and soft x-ray emission. The increased emission was concentrated in the plasma core region. A heating efficiency of over 50% was achieved, when the density gradient in the MC region was sufficiently steep.     

On the parametric excitation of surface oscillations of a cold plasma

The excitation of surface oscillations of cold plasmas is studied for external electric fields perpendicular to the plasma density gradient. Boundary conditions for electromagnetic fields on the plane boundary between plasmas with different densities are derived, and the dispersion relation for the excitation of the surface modes is obtained. The effects of metallic walls of a vacuum chamber are considered, together with the excitation of surface oscillations of a plasma slab immersed in a plasma with different density.     

Parametric excitation of relativistic plasma oscillations by strong electromagnetic waves

Parametric interaction of strong waves ($\text{?=}\text{eE}{}_{\mathrm{<mtext>o</mtext>}}\text{m}{}_{\mathrm{<mtext>e</mtext>}}\text{cω}{}_{\mathrm{<mtext>o</mtext>}}\text{～ 1}$) with a cold, two-fluid (ion and electron) plasma is studied in the limits of high frequency (ω_o?ω_Le) and resonance (ω_o ≈ ω_Le). Unstable oscillations of both electrons and ions are found in the resonance limit.     

Nonlinear dispersion in the process of quasistationary excitation of plasma waves

A quasistationary problem of Lengmuir wave excitation by external sources in uniform plasma is considered. It is established that energy is transferred from external sources to the wave if during its excitation the wave phase velocity changes in addition to an increase in the wave amplitude. A nonlinear dispersion equation for the plasma wave of finite amplitude excited by the external sources is derived. The nonlinear contribution of this dispersion equation is caused not only by an increase in the wave amplitude but also by the wave frequency shift.     

Ion wave excitation by radiation pressure in a plasma waveguide

After turn-off of high-power pulsed microwaves, a large-amplitude ion wave is generated which has half of the wavelength of the guided wave. The electromagnetic radiation pressure is responsible for the excitation of the ion acoustic wave.     

The influence of striction density perturbations on the excitation of plasma oscillations inside thermal inhomogeneities of plasma

In this paper, we continue our studies begun in [Izv. Vyssh. Uchebn. Zaved., Radiofiz.,41, No. 3, 270 (1998)].Calculating the coefficients and nonlinear phase shift in the equation for plasma-wave intensity introduced in the eralier paper, we have solved the problem of the influence of striction perturbations of the plasma density on the excitation of shortwave plasma oscillations by an electromagnetic wave; the above oscillations are captured in a volume of inhomogeneities, which are extended along the magnetic field and have reduced electron density that crosses the level of the upper-hybrid resonance. The dissipative processes of absorption and emission of plasma waves beyond the inhomogeneity are assumed to be weak. The variation of excitation and reflection of plasma waves from the resonance level due to deformation of the plasma- density profile is described. The band of effective generation of eigenmodes of captured oscillations as a function of the total wave-phase increment in an inhomogeneity is determined. The effect of penetration of the field of a high-power plasma wave into the non-transmittance region as a result of the striction expulsion of plasma is calculated. With allowance for the nonlinear phenomena in question, we estimated the heating of artificial inhomogeneities of thermal origin as a result of collisional absorption of the plasma oscillations excited in a volume of inhomogeneities under the action of a high-power radio wave. The materials of this paper were reported at the IIIrd International School on Space Plasma Physics. Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow Region, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 10, pp. 1226–1247, October 1998.     

Resonant generation of plasma oscillations by a plane gravitational wave

An exact solution of the universal Maxwell equations linearized in the amplitude of the induced field is found with the help of a previously found exact solution of the kinetic equation with a model collision integral. Two oscillation modes arise under the action of a gravitational wave in a plasmalike medium: an undamped wave with the frequency of the gravitional wave and a damped one with the plasma frequency. When these frequencies coincide, a resonance arises, as a result of which the amplitude of the electric oscillations increases sharply.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 74–77, January, 1985.     

Parametric excitation of subharmonic oscillations

Subharmonic oscillations of order one-half for a single-degree-of-freedom system with quadratic, cubic, and quartic nonlinearities under parametric excitation are investigated. Two approximate methods (multiple scales and generalized synchronization) are used for comparison. The modulation equations (reduced equations) of the amplitudes and the phases are obtained. Steady-state solutions (periodic solutions) and their stability are determined. Numerical solutions are carried out, and graphical representations of the results are presented and discussed. The results obtained by the two methods are in excellent agreement.     

Terahertz wave generation via pre-ionized air plasma

We report the terahertz(THz) wave generation from a single-color scheme modulated by pre-ionized air plasma via an orthogonal pumping geometry. It is found that the amplitude of the THz signal generated by the pump beam tends to decrease gradually with the increase of the modulation power. We believe that the ponderomotive force plays an important role in the process of the interaction between the pump beam and the pre-ionization beam. The hydrostatic state of the electrostatic separation field caused by the modulation beam will directly affect the generation efficiency of the THz wave. Our results contribute to further understanding of the theoretical mechanism and expanding of the practical applications of THz wave generation and modulation.     

Debye等离子体中高能H++H碰撞激发过程的研究

利用碰撞参数玻恩近似方法研究了Debye 等离子体环境中高能H⁺+H的碰撞激发过程, 研究了不同Debye 半径下氢原子1s → 2p 的激发耦合相互作用矩阵元、入射粒子能量为160 keV/u 的激发电子跃迁概率以及入射粒子能量范围为100–1000 keV/u 的碰撞激发截面. 结果表明: 随着屏蔽效应的增强, 激发截面减小. 根据激发截面的公式以及计算结果详细分析了引起激发截面减少的原因. 入射粒子与激发电子之间的屏蔽相互作用势和靶的电子结构(波函数和能级) 对激发截面都有很重要的影响. 关键词： 等离子体 碰撞参数玻恩近似方法 碰撞激发截面     

Ion sound wave excitation in a plasma under a Langmuir turbulence regime

Ion sound wave excitation in a warm non-relativistic (W_b ≤ 400 eV) electron beam unmagnetized plasma system is studied experimentally. The spectrum of these waves shows two peaks at frequencies of 70 and 230 kHz respectively. The origin of these waves is connected with modulational instability and cavity collapse. We show that the energy of bulk accelerated electrons can explain the measured value of kr_De for high-frequency sound waves. The energy of ion sound waves is not high enough to have an influence on the Langmuir turbulence dynamics.     

On the excitation of density oscillations in nuclear matter

The possibility of the exciting small density oscillations in cold nuclear matter is investigated within the frame of the Landau theory, assuming F_l = 0 for l > 2. These excitations may propagate for F₀ ? 1 (K ? 576 MeV and are strongly damped for F₀ which does not fulfill this inequility.     

A numerical simulation of surface wave excitation in a rectangular planar-type plasma source

The principle of surface wave plasma discharge in a rectangular cavity is introduced simply based on surface plasmon polariton theory. The distribution of surface-wave electric field at the interface of the plasma-dielectric slab is investigated by using the three-dimensional finite-difference time-domain method (3D-FDTD) with different slot-antenna structures. And the experimental image of discharge with a novel slot antenna array and the simulation of the electric field with this slot antenna array are both displayed. Combined with the distribution of surface wave excitation and experimental results, the numerical simulation performed by using 3D-FDTD is shown to be a useful tool in the computer-aided antenna design for large area planar-type surface-wave plasma sources.     

Wavenumber oscillations of a linear electron plasma testwave in the presence of a standing large-amplitude wave

A linear electron plasma testwave coexisting with a standing large-amplitude wave shows wavenumber oscillations which may be explained by stationary axial plasma density variations being produced by the pump wave via the ponderomotive force.     

Dissipation of the excitation wave fronts

An excitation wave in cardiac tissue will fail to propagate if the transmembrane voltage at its front rises too slowly and does not excite the tissue ahead of it. Then the sharp voltage profile of the front will dissipate, and the subsequent spread of voltage will be purely diffusive. This mechanism is impossible in FitzHugh-Nagumo type systems. Here a simplified mathematical model for this mechanism is suggested. The model has exact traveling front solutions, and gives conditions for the front dissipation. In particular, a front will dissipate if it is not allowed to propagate faster than a certain nonzero speed. This critical speed depends only on the properties of the fast sodium current.