Nonlinear dynamics of filamentation instability and current filament merging in a high density current-driven plasma

The magnetic field generation due to the filamentation instability (FI) of a high density current-driven plasma is studied through a new nonlinear diffusion equation. This equation is obtained on the basis of quantum hydrodynamic model and numerically solved by applying the Crank–Nicolson method. The spatiotemporal evolution of the magnetic field and the electron density distribution exhibits the current filament merging as a nonlinear phase of the FI which is responsible for the strong magnetic fields in the current-driven plasmas. It is found that the general behaviour of the FI is the same as that of the classical case but the instability growth rate, its magnitude, and the saturation time are affected by the quantum effects. It is eventually concluded that the quantum effects can play a stabilizing role in such situation.     

Two-stream instabilities in degenerate quantum plasmas

The quantum effects on the plasma two-stream instability are studied by the dielectric function approach. The analysis suggests that the instability condition in a degenerate dense plasma deviates from the classical theory when the electron drift velocity is comparable to the Fermi velocity. Specifically, for a high wave vector comparable to the Fermi wave vector, a degenerate quantum plasma has larger regime of instability than predicted by the classical theory. A regime is identified, where there are unstable plasma waves with frequency 1.5 times of a normal Langmuir wave.     

Modulation instability of lower hybrid waves leading to cusp solitons in electron–positron(hole)–ion Thomas Fermi plasma

Following the idea of three‐wave resonant interactions of lower hybrid waves, it is shown that quantum‐modified lower hybrid (QLH) wave in electron–positron–ion plasma with spatial dispersion can decay into another QLH wave (where electron and positrons are activated, whereas ions remain in the background) and another ultra‐low frequency quantum‐modified ultra‐low frequency Lower Hybrid (QULH) (where ions are mobile). Quantum effects like Bohm potential and Fermi pressure on the lower hybrid wave significantly reshaped the dispersion properties of these waves. Later, a set of non‐linear Zakharov equations were derived to consider the formation of QLH wave solitons, with the non‐linear contribution from the QLH waves. Furthermore, modulational instability of the lower hybrid wave solitons is investigated, and consequently, its growth rates are examined for different limiting cases. As the growth rate associated with the three‐wave resonant interaction is generally smaller than the growth associated with the modulational instability, only the latter have been investigated. Soliton solutions from the set of coupled Zakharov and NLS equations in the quasi‐stationary regime have been studied. Ordinary solitons are an attribute of non‐linearity, whereas a cusp soliton solution featured by nonlocal nonlinearity has also been studied. Such an approach to lower hybrid waves and cusp solitons study in Fermi gas comprising electron positron and ions is new and important. The general results obtained in this quantum plasma theory will have widespread applicability, particularly for processes in high‐energy plasma–laser interactions set for laboratory astrophysics and solid‐state plasmas.     

Lower hybrid wave instability in a spin‐polarized degenerate plasma

Lower hybrid (LH) wave instability excited due to an electron beam in a spin‐polarized degenerate plasma is studied. Using the Separate Spin Evolution quantum hydrodynamic model, incorporating Coulomb exchange interaction and Bohm potential, the general dispersion relation of nearly perpendicular propagating electrostatic waves is derived. Furthermore, in the low‐frequency limit, the dispersion of LH wave is obtained. It is found that the electron spin polarization and beam streaming speed reduce the growth rate as well as the k‐domain. However, the beam density and the propagation angle enhance both the growth rate and k‐domain of LH instability. In addition, the contribution of the Bohm potential term increases the intensity of the growth rate. All these effects may have a strong bearing on the wave and instability phenomena in spin‐polarized plasmas.     

Effect of short-wavelength Langmuir turbulence on the Brillouin backscattering and filamentation instabilities in homogeneous plasmas

The Brillouin backscattering and the filamentation instabilities in the presence of short-wavelength Langmuir turbulence are investigated for a homogeneous plasma. Analytical results for the growth rates and thresholds are obtained. It is shown that the threshold for Brillouin backscattering can be significantly increased because of the anomalous damping of ion-acoustic perturbations by Langmuir turbulence. For the filamentation instability an enhancement of the growth rate is obtained. The effect of short-wavelength ion wave turbulence is also discussed.     

超强线极化激光在e-p等离子体中传播的成丝不稳定性

基于超强线极化激光在正负电子对(e-p)等离子体中的传播方程,讨论了相互作用过程中的成丝不稳定性。得到了电磁波的非线性色散关系和不稳定性增长率,并讨论了传播过程中激光强度和等离子体温度对成丝不稳定性的影响。结果表明,成丝不稳定性的强弱主要由相互作用的非线性效应与受有质动力作用后等离子体密度的减小之间的竞争所决定。     

PIC Simulation of Current‐Driven Buneman Instability in Presence of Collisional and Thermal Effects

Collisional and thermal effects on the nonlinear evolution of Buneman instability in an unmagnetized current‐driven plasma are investigated by particle in cell simulations. These simulations show that, as the time passes, the electron distribution function profiles deviate from initial shifted Maxwellian distribution and the electron phase‐space holes can be formed. The electron distribution function profiles also indicate the counter‐streaming and plateau formation. Moreover, the contour of the electric field and profiles of the growth rate display the resonance condition for this instability. Finally, the time evolution of the electric field energy density and ion kinetic energy in the presence of collisional and thermal effects are presented. These evolutions illustrate that in the presence of collisions, the growth rate of the Buneman instability is smaller than the collisionless case. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solar wind driven electrostatic instabilities with generalized (r,q) distribution function

Using Boltzmann–Vlasov kinetic model, a currentless ion acoustic instability driven by stream of solar wind plasma is studied in a non‐thermal distributed electrons and ions. The non‐thermal distribution considered here is the generalized distribution which has low energetic flat‐top and velocity power law tail at higher energies. The instability threshold is found to be affected and depends upon the spectral indices r and q . It is found that the growth rate increases with the decrease in the value of r and increase with q . Moreover, such kinetic instability has also been discussed for three species electron–ion–dust plasma using the generalized (r, q) distribution function. Such case is of interest when the solar wind is streaming through the cometary plasma in the presence of interstellar dust and excites electrostatic instabilities. The dispersion properties and growth rates for ion‐acoustic and dust‐acoustic mode are calculated analytically and plotted for different values of the spectral indices r and q .     

Relativistic effects on the modulational instability of electron plasma waves in quantum plasma

Relativistic effects on the linear and nonlinear properties of electron plasma waves are investigated using the one-dimensional quantum hydrodynamic (QHD) model for a two-component electron?Cion dense quantum plasma. Using standard perturbation technique, a nonlinear Schr?dinger equation (NLSE) containing both relativistic and quantum effects has been derived. This equation has been used to discuss the modulational instability of the wave. Through numerical calculations it is shown that relativistic effects significantly change the linear dispersion character of the wave. Unlike quantum effects, relativistic effects are shown to reduce the instability growth rate of electron plasma waves.     

黑腔中空间束匀滑光束成丝不稳定性的数值模拟北大核心CSCD

为深入研究黑腔内激光成丝不稳定性产生和发展,建立了空间束匀滑光束的传播模型,利用三维激光等离子体相互作用程序LAP3D模拟了黑腔物理条件下的大尺度成丝现象。模拟结果可正确描述成丝后光强的束发散现象及谱空间光强分布特征。从激光能量参数角度分析了导致成丝不稳定性发展的物理因素,并讨论了应用空间束匀滑技术抑制成丝不稳定性的局限性。研究表明:空间束匀滑光束发展成丝的能力取决于光斑内小焦斑的成丝表现,当具备成丝能力的小焦斑份额达到一定比例后,就会导致整个空间束匀滑光束成丝,因此对于光斑平均功率密度较高的光束,须考虑结合其他束匀滑手段来抑制成丝发展。     

FILAMENTATION INSTABILITY OF LASER BEAMS IN NONLOCAL NONLINEAR MEDIA

The filamentation instability of laser beams propagating in nonlocal nonlinear media is investigated. It is shown that the filamentation instability can occur in weakly nonlocal self-focusing media for any degree of nonlocality, and in defocusing media for the input light intensity exceeding a threshold related to the degree of nonlocality. A linear stability analysis is used to predict the initial growth rate of the instability. It is found that the nonlocality tends to suppress filamentation instability in self-focusing media and to stimulate filamentation instability in self-defocusing media. Numerical simulations confirm the results of the linear stability analysis and disclose a recurrence phenomenon in nonlocal self-focusing media analogous to the Fermi-Pasta-Ulam problem.     

强激光部分离化等离子体成丝不稳定性

从部分离化等离子体和通常的全离化等离子体的差异是存在束缚电子出发,分析强激光在部分离化等离子体中的传播和折射指数,其束缚电子加强成丝不稳定性的发展.对钕玻璃三倍频激光金靶等离子体的原子成丝不稳定性进行了计算和分析.结果表明强激光部分离化等离子体的原子成丝不稳定性显著高于相对论成丝不稳定性. 关键词： 激光等离子体相互作用 部分离化等离子体 成丝不稳定性     

Rayleigh-Taylor/gravitational instability in dense magnetoplasmas

The Rayleigh-Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh-Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.     

Ion waves driven by shear flow in a relativistic degenerate astrophysical plasma

We investigate the existence and propagation of low-frequency (in comparison to ion cyclotron frequency) electrostatic ion waves in highly dense inhomogeneous astrophysical magnetoplasma comprising relativistic degenerate electrons and non-degenerate ions. The dispersion equation is obtained by Fourier analysis under mean-field quantum hydrodynamics approximation for various limits of the ratio of rest mass energy to Fermi energy of electrons, relevant to ultra-relativistic, weakly-relativistic and non-relativistic regimes. It is found that the system admits an oscillatory instability under certain condition in the presence of velocity shear parallel to ambient magnetic field. The dispersive role of plasma density and magnetic field is also discussed parametrically in the scenario of dense and degenerate astrophysical plasmas.     

Filamentation and stimulated Brillouin scattering in a turbulent plasma

This paper presents a theory of filamentation and stimulated Brillouin scattering (SBS) of high-frequency electromagnetic radiation in a weakly collisional plasma with ion-acoustic turbulence. When the square of the wavelength of the plasma perturbations is less than the product of the two mean free path lengths of an electron with respect to its collisions with turbulent fluctuations and with electrons, the influence of cold highly collisional electrons on the parametric instabilities becomes apparent. It is shown that the plasma turbulence lowers the filamentation threshold, and the SBS threshold can be either lowered or raised. The dependence of the SBS and filamentation thresholds on the electron mean free path length in the turbulent plasma and on the anisotropy of the plasma turbulence is determined. The corresponding dependence of the spatial scale of the most efficiently growing filaments and their spatial growth rate are found. Zh. éksp. Teor. Fiz. 113, 629–645 (February 1998)     

Dust-lower-hybrid waves in quantum plasmas

The dispersion relation of the dust-lower-hybrid wave has been derived using the quantum hydrodynamic model of plasmas in an ultracold Fermi dusty plasma in the presence of a uniform external magnetic field. The dust dynamics, electron Fermi temperature effect, and the quantum corrections give rise to significant effects on the dust-lower-hybrid wave of the magnetized quantum dusty plasmas.     

Investigation of the particle spin properties on the velocity space instability in high‐density plasmas

The nonresonant electromagnetic instabilities of the anisotropic velocity space (Weibel‐like) have always been one of the interesting subjects for researchers. These electromagnetic instabilities play an important role in generating strong magnetic fields in laboratory plasmas for applications such as inertial confinement fusion and space plasmas. In this paper, we investigate the quantum effects of the particle spin on the electromagnetic instabilities. In the case of the presence of a magnetic dipole force and an electron precession frequency like the Vlasov equation, we derive the full quantum equation. This study shows that, in the presence of the spin‐polarized effects, the growth rate of the instabilities is reduced compared to the classical cases and will not arise for low fractions of the temperature anisotropy for different values of the magnetic field. Indeed, it is expected that the probability of electron capture in the background magnetic fields and the effective collision with the particle increase because of the spin effect, so that a high portion of the electron energy is transmitted to the background plasma, and the temperature anisotropy governing the electron distribution is reduced.     

Interplay of collisions and temperature on the filamentary structures of a relativistic electron beam in plasmas

A systematic study on the Weibel instability induced filamentation of a relativistic electron beam is made by including the effects of collisions and temperature. The stabilization and de-stabilization of the beam filamentation due to beam temperature and plasma collisions, respectively, is explored through an analytical model and PIC simulations. The de-stabilization of the beam filamentation is attributed to the collision driven negative energy wave generation in the beam plasma system.     

Boundary graphene layer effect on surface plasmon oscillations in a quantum plasma half-space

The effect of graphene on unique features of surface plasmon-polariton excitations near the interface of vacuum and quantum plasma half-space is explored using a quantum hydrodynamic model including the Fermi electron temperature and the quantum Bohm potential together with the full set of Maxwell equations.It is found that graphene as a conductive layer significantly modifies the propagation properties of surface waves by making a change on the corresponding wave dispersion relation.It is shown that the presence of graphene layer on the interface of vacuum and plasma leads to a blue-shift in the surface Plasmon frequency.The results of present study must be contributed to the modern electronic investigations.     

Drift wave turbulence in a dense semi-classical magnetoplasma

A semi-classical nonlinear collisional drift wave model for dense magnetized plasmas is developed and solved numerically. The effects of fluid electron density fluctuations associated with quantum statistical pressure and quantum Bohm force are included, and their influences on the collisional drift wave instability and the resulting fully developed nanoscale drift wave turbulence are discussed. It is found that the quantum effects increase the growth rate of the collisional drift wave instability, and introduce a finite de Broglie length screening on the drift wave turbulent density perturbations. The relevance to nanoscale turbulence in nonuniform dense magnetoplasmas is discussed.