Acousto-electric wave instability in ion-implanted semiconductor plasmas

A comprehensive investigation of excitation of acousto-electric modes and novel properties introduced due to presence of negatively charged colloids in magnetized compensated piezoelectric semiconductor plasma is presented analytically. We derive a compact dispersion relation for the acousto-electric waves in colloids laden semiconductor plasma by employing multi-fluid balance equation. It is found that the presence of charged colloids not only modifies the wave spectrum but also alters the amplification characteristics even though colloidal particles, on account of their heavy masses, do not participate in wave propagation. The results of this investigation should be useful in understanding the characteristics of longitudinal acousto-electric wave in ion-implanted piezoelectric semiconductor plasmas whose main constituents are electrons, holes and negatively charged colloids, which are stationary in the background.     

Excitation of accelerating wakefields in inhomogeneous plasmas

The excitation of the wakefields in an inhomogeneous plasma by a short laser pulse is investigated theoretically. A general equation for the wake excitation in transversely nonuniform plasma is derived. This equation is applied to the step-function density profile model of hollow channel laser wakefield accelerator. A more realistic model, in which the transition between the evacuated channel and the homogeneous surrounding plasma occurs over a finite radial extent, is then analyzed. It is shown that the excited channel made can interact resonantly with the plasma electrons inside the channel wall, leading to secular growth of the electric field. This eventually results in wavebreaking and the dissipation of the accelerating mode. We introduce an effective quality factor Q for the hollow channel laser wakefield geometry. This resonance limits the number of electron bunches that can be accelerated in the wake of single laser pulse     

Plasma-maser instability in dusty plasmas

The growth rates of the Langmuir and electromagnetic radiation due to the plasma-maser instability in multicomponent unmagnetized plasmas with stationary charged particulates are obtained. The up-conversion of the wave energy from ion-acoustic oscillations to the test Langmuir and electromagnetic waves is much enhanced owing to the enhanced accelaration of electrons by the dust ion-acoustic mode. The results could be important for the interpretation of high-frequency waves in space and astrophysical dusty plasmas.     

Filamentation instability due to compressional Alfvén wave in laser heating of plasmas

It is shown that the filamentation instability of a high frequency pump wave can have an exceptionally low threshold intensity in a magnetized plasma. The excitation of a purely growing mode may have important consequences in the laser heating schemes of pinch devices.     

Propagation dynamics of relativistic electromagnetic solitary wave as well as modulational instability in plasmas

By one-dimensional particle-in-cell(PIC) simulations, the propagation and stability of relativistic electromagnetic(EM) solitary waves as well as modulational instability of plane EM waves are studied in uniform cold electron-ion plasmas.The investigation not only confirms the solitary wave motion characteristics and modulational instability theory, but more importantly, gives the following findings. For a simulation with the plasma density 10²³ m^-3 and the dimensionless vector potential amplitude 0.18, it is found that the EM solitary wave can stably propagate when the carrier wave frequency is smaller than 3.83 times of the plasma frequency. While for the carrier wave frequency larger than that, it can excite a very weak Langmuir oscillation, which is an order of magnitude smaller than the transverse electron momentum and may in turn modulate the EM solitary wave and cause the modulational instability, so that the solitary wave begins to deform after a long enough distance propagation. The stable propagation distance before an obvious observation of instability increases(decreases) with the increase of the carrier wave frequency(vector potential amplitude). The study on the plane EM wave shows that a modulational instability may occur and its wavenumber is approximately equal to the modulational wavenumber by Langmuir oscillation and is independent of the carrier wave frequency and the vector potential amplitude.This reveals the role of the Langmuir oscillation excitation in the inducement of modulational instability and also proves the modulational instability of EM solitary wave.     

Streaming instability in quantum dusty plasmas

By using a quantum hydrodynamic (QHD) model, we derive a generalized dielectric constant for an unmagnetized quantum dusty plasma composed of electrons, ions, and charged dust particulates. Neglecting the electron inertial force in comparison with the electron pressure, and the force associated with the electron correlations at a quantum scale, we discuss two classes of electrostatic instabilities that are produced by streaming ions, and dust grains. The effects of the plasma streaming speeds, the thermal speed of electrons, and the quantum parameter are examined on the growth rates. The relevance of our investigation to dense astrophysical plasmas is discussed.     

Resistive lower-hybrid instability in current-carrying plasmas

Obliquely propagating lower hybrid waves are found to be unstable in a collisional, fully-ionized plasma carrying a field-aligned current.     

Hydromagnetic instability of contra-streaming plasmas

The stability of the system consisting of two contra-streaming plasmas is discussed in the limit of low-frequency perturbations. The existence of an external magnetic field parallel to the velocity of the contra-streaming is admitted. It is shown that the system is unstable whenever the density of kinetic energy belonging to the relative motion of the two plasmas exceeds the magnetic energy density. This is true even when the system is stable in the sense of Penrose's criterion [1].     

Nonlinear wave modulations in plasmas

A review of the generic features as well as the exact analytical solutions of coupled scalar field equations governing nonlinear wave modulations in plasmas is presented. Coupled sets of equations like the Zakharov system, the Schrödinger-Boussinesq system and the Schrödinger-KDV system are considered. For stationary solutions, the latter two systems yield a generic system of a pair of coupled, ordinary differential equations with many free parameters. Different classes of exact analytical solutions of the generic system which are valid in different regions of the parameter space are obtained. The generic system is shown to generalize the Hénon-Heiles equations in the field of nonlinear dynamics to include a case when the kinetic energy in the corresponding Hamiltonian is not positive definite. The relevance of the generic system to other equations like the self-dual Yang-Mills equations, the complex KDV equation and the complexified classical dynamical equations is also pointed out.     

Filamentation instability in two counter-streaming laser plasmas

The filamentation instability was observed in the interaction of two counter-streaming laser ablated plasma flows,which were supersonic, collisionless, and also closely relevant to astrophysical conditions. The plasma flows were created by irradiating a pair of oppositely standing plastic(CH) foils with 1ns-pulsed laser beams of total energy of 1.7 k J in two laser spots. With characteristics diagnosed in experiments, the calculated features of Weibel-type filaments are in good agreement with measurements.     

Field compressing magnetothermal instability in laser plasmas

The mechanism for a new instability in magnetized plasmas is presented and a dispersion relation derived. Unstable behavior is shown to result purely from transport processes-feedback between the Nernst effect and the Righi-Leduc heat-flow phenomena in particular-neither hydrodynamic motion nor density gradients are required. Calculations based on a recent nanosecond laser gas-jet experiment [D. H. Froula, Phys. Rev. Lett. 98, 135001 (2007)] predict growth of magnetic field and temperature perturbations with typical wavelengths of order 50 μm and characteristic growth times of ～0.1 ns. The instability yields propagating magnetothermal waves whose direction depends on the magnitude of the Hall parameter.     

Magneto-Rayleigh-Taylor instability in compressible Z-pinch liner plasmas

In this paper, the characteristics of magneto-Rayleigh-Taylor(MRT) instability of liner plasmas in Mag LIF is theoretically investigated. A three-region slab model, based on ideal MHD equations, is used to derive the dispersion relation of MRT instability. The effect of compressibility on the development of MRT instability is specially examined. It is shown that the growth rate of MRT instability in compressible condition is generally lower than that in incompressible condition in the presence of magnetic field. In the case of zero magnetic field, the growth rate in compressible assumption is approximately the same as that in incompressible assumption. Generally, MRT instability in(x, y) plane can be remarkably mitigated due to the presence of magnetic field especially for short-wavelength perturbations. Perturbations may be nearly completely mitigated when the magnetic field is increased to over 1000 T during liner implosions. The feedthrough of MRT instability in liner outer surface on inner surface is also discussed.     

Magnetoacoustic waves with effect of arbitrary degree of temperature and spin degeneracy in electron-positron-ion plasmas

The linear properties of magnetosonic waves are studied in nearly degenerate and nearly non-degenerate quantum plasmas composed of electrons, positrons and ions in the presence of spin- effect. Using the fluid equations, a generalized dispersion relation for perpendicular and oblique propagation is derived. It is found that degree of temperature and spin degeneracy modify the dispersive properties of the given modes. The results of analysis are beneficial for understanding the collective phenomena in dense quantum astrophysical plasmas.     

Entropy maximization and instability in uniformly magnetized plasmas

A regime in which a uniformly magnetized plasma does not maximize the entropy and possibly becomes unstable to a spatial perturbation in the magnetic field is explored. The physical implication is considered in the context of current generation, magnetic field reconnection, and the dynamo effect.     

Resistive electromagnetic ion cyclotron instability in counterstreaming plasmas

Obliquely propagating electromagnetic ion cyclotron waves are found to be unstable in a collisional, fully-ionized plasma consisting of two electron beams counterstreaming along an external magnetic field in a background of stationary ions.     

Raman scattering and two-plasmon instability in laser-created plasmas

Couplings in which a plasma wave can be generated through either one of two mechanisms are investigated. It is shown that the Raman up-conversion associated with the two-plasmon decay might account for the observation of the 3 ω₀/2 harmonic.     

On the filamentation instability in degenerate relativistic plasmas

The filamentation instability of the electromagnetic (EM) beam in an underdense plasma with high level of degeneracy is examined by means of the momentum equation, continuity equation and Maxwell's equations. It has been demonstrated that the instability develops for weakly as well as strongly relativistic degenerate plasma and arbitrary strong amplitude of EM beams.