Plasma Dielectric Function Research Articles

Coupling of Upper Hybrid Surface Plasmon Modes in Magnetoplasma Waveguide Structure

Abstract: We investigate the spectra of high-frequency electrostatic surface electron plasmon oscillations propagating normal to a dc-magnetic field. These oscillations are supported by two identical magnetoplasma slabs separated by a vacuum slab. Propagation characteristics of surface magnetoplasma oscillations and their coupling are studied by simultaneously solving the homogeneous system of equations obtained by matching the electrostatic fields at the interfaces together with the warm plasma dielectric function of upper hybrid waves. We demonstrate the existence of two propagating magnetoplasma electrostatic surface modes (backward and forward modes). The backward mode emerges at frequency ω=ω_uh=√(ω_pe^2+ω_ce^2 ), where ω_pe and ω_ce are the electron plasma frequency and the electron cyclotron frequency, respectivily, and the forward propagating mode emerges at a lower frequency ω=ω_uh-ω_pe. The forward and backward surface modes become coupled and form a single mode at upper hybrid resonance quasi-static value ω=ω_uh/√2. Keywords: Upper hybrid modes, Plasma slab waveguide, Coupled plasmon surface modes.

Self-focusing of high power beam in unmagnetized plasma and its effect on Stimulated Raman scattering process

In present study, Self-focusing of high power beam in unmagnetized plasma and its effect on Stimulated Raman scattering (SRS) process is investigated. Both relativistic-ponderomotive nonlinearities are taken together. Electron plasma wave (EPW) interacts nonlinearly with pump beam thereby leading to SRS. Under combined action of relativistic-ponderomotive forces, nonlinearity in plasma dielectric function is set up. This further causes change in plasma’s density profile in perpendicular direction to pump beam axis. This modification greatly influences input beam, scattered beam and EPW. Nonlinear differential equations for input beam, scattered beam and EPW are set up using Wentzel Kramers Brillouin approximation and paraxial theory. Numerical simulations are executed for analyzing effect of well-known parameters of laser and plasma medium on focusing/defocusing of various beams involved in the process and SRS back-reflectivity. It is confirmed that focusing of beams involved raises SRS back-reflectivity.

Characteristics of Thomson scattering in degenerate quantum plasmas: Quantum-recoil effect

The quantum-recoil effect on Thomson scattering is investigated in degenerate quantum plasmas. The Thomson scattering cross-section in degenerate quantum plasmas is obtained by the fluctuation-dissipation relation and plasma dielectric function as a function of the plasmon energy, Fermi energy, wave number, and scattering angle. It is shown that the influence of the quantum recoil suppresses the Salpeter structure factor in degenerate quantum plasmas. It is also shown that the structure factor and the differential Thomson scattering cross-section decrease with an increase of the Fermi energy. In addition, it is found that the influence of the Fermi energy on the differential Thomson scattering cross-section is important in the backward scattering regions. Moreover, the total Thomson scattering cross-section has been shown to increase as the scaled plasmon energy increases in degenerate quantum plasmas.

Turning point temperature of self-focusing at laser–plasma interaction with weak relativistic-ponderomotive nonlinearity: effect of light absorption

In this communication, we have examined the influence of light absorption on turning point temperature of self-focusing in the interaction of Gaussian laser beam in plasma. The dielectric function of plasma introduced herein is under weak relativistic and ponderomotive regime. Differential equation for beam-width parameter has been established by using parabolic equation approach under WKB and paraxial approximations. Numerical analysis shows that light absorption plays an important role on turning point temperature of self-focusing under relativistic and ponderomotive regime. It is also found that variation of normalized plasma density, normalized laser intensity parameter and plasma dielectric function with dimensionless distance of propagation gives reasonably interesting results.

Dust-charge fluctuation effects on surface dust-acoustic waves in astrophysical half-space dusty plasmas

We investigate the dust-charge fluctuation effects on the propagation and the decay of the dust-acoustic surface plasma wave at the interface of plasma-vacuum in astrophysical half-space dusty plasmas. The dispersion relation for the surface mode is derived by using the appropriate plasma dielectric function. We found that wave frequency decreases as the dust-charging frequency increases as well as the dynamical wave number does. However, the damping rate of the surface wave increases with an increase of the dust-charging frequency and the dynamical wave number. Hence, the amplitude of the surface wave is found to be strongly suppressed with an increase of the dust-charging frequency. The increase of charging relaxation rate is found to suppress both of the real frequency of the wave and the damping rate of the surface wave in astrophysical half-space dusty plasmas.

Impact of quantum non‐locality and electronic non‐ideality on e–He scattering in a dense plasma

The screened Hartree–Fock potential and the polarization potential for the description of the electron–helium scattering in dense plasmas are derived. The effects of quantum non‐locality and correlations of free electrons are taken into account in the plasma dielectric function. Plasma polarization leads to a significant increase in the transport cross‐section at small wave numbers ka < 2 in comparison with the case of an electron scattering on the isolated atom, where a is the mean distance between plasma electrons. It is shown that taking into account the quantum non‐locality and correlations is important at ka < 2.

Stable and unstable roots of ion temperature gradient driven mode using curvature modified plasma dispersion functions

Basic, local kinetic theory of ion temperature gradient driven (ITG) mode, with adiabatic electrons is reconsidered. Standard unstable, purely oscillating as well as damped solutions of the local dispersion relation are obtained using a bracketing technique that uses the argument principle. This method requires computing the plasma dielectric function and its derivatives, which are implemented here using modified plasma dispersion functions with curvature and their derivatives, and allows bracketing/following the zeros of the plasma dielectric function which corresponds to different roots of the ITG dispersion relation. We provide an open source implementation of the derivatives of modified plasma dispersion functions with curvature, which are used in this formulation. Studying the local ITG dispersion, we find that near the threshold of instability the unstable branch is rather asymmetric with oscillating solutions towards lower wave numbers (i.e. drift waves), and damped solutions toward higher wave numbers. This suggests a process akin to inverse cascade by coupling to the oscillating branch towards lower wave numbers may play a role in the nonlinear evolution of the ITG, near the instability threshold. Also, using the algorithm, the linear wave diffusion is estimated for the marginally stable ITG mode.

Backward propagating branch of surface waves in a semi-bounded streaming plasma system

The influence of wake and magnetic field on the surface ion-cyclotron wave is kinetically investigated in a semi-bounded streaming dusty magnetoplasma in the presence of the ion wake-field. The analytic expressions of the frequency and the group velocity are derived by the plasma dielectric function with the spectral reflection condition. The result shows that the ion wake-field enhances the wave frequency and the group velocity of the surface ion-cyclotron wave in a semi-bounded dusty plasma. It is found that the frequency and the group velocity of the surface electrostatic-ion-cyclotron wave increase with an increase of the strength of the magnetic field. It is interesting to find out that the group velocity without the ion flow has the backward propagation mode in a semi-bounded dusty plasma. The variations due to the frequency and the group velocity of the surface ion-cyclotron wave are also discussed.

Nonlinear frequency shift of electrostatic waves in general collisionless plasma: Unifying theory of fluid and kinetic nonlinearities

The nonlinear frequency shift is derived in a transparent asymptotic form for intense Langmuir waves in general collisionless plasma. The formula describes both fluid and kinetic effects simultaneously. The fluid nonlinearity is expressed, for the first time, through the plasma dielectric function, and the kinetic nonlinearity accounts for both smooth distributions and trapped-particle beams. Various known limiting scalings are reproduced as special cases. The calculation avoids differential equations and can be extended straightforwardly to other nonlinear plasma waves.

Dual-mode characteristics of the Buneman instability in a bounded slab plasma

The dual-mode characteristics of the Buneman instability are investigated in a slab plasma, including the geometric effects. The dual symmetric and anti-symmetric dispersion modes of the Buneman instability are obtained by the plasma dielectric function with the spectral reflection conditions for the slab geometry. The result shows that the magnitudes of the growth rate for the symmetric mode are always greater than those for the anti-symmetric mode. It is also found that the geometric effect suppresses the position of the maximum growth rate for the Buneman instability in bounded slab plasmas since the maximum conditions for the symmetric and anti-symmetric modes of the Buneman instability are given by 0.60<kzv0/ωpe<0.65. The physical characteristics and properties of the dual modes of the Buneman instability are also discussed.

Effect of light absorption on relativistic self-focusing of Gaussian laser beam in plasma

In the present paper, we have studied the effect of light absorption on relativistic self-focusing of Gaussian laser beam propagating through plasma. We have obtained the differential equation for beam width parameter by using parabolic equation approach under the usual WKB and paraxial approximations. The effect of light absorption on the behavior of beam-width parameter, normalized intensity and plasma dielectric function is presented graphically and discussed. It shows that absorption play an important role in weakening the relativistic self-focusing of laser beam during propagation in plasma and gives reasonably interesting results.

Influence of electron-neutral collisions on the Compton scattering cross section and the Salpeter structure factor in warm collisional plasmas

The electron-neutral collision effects on the Compton scattering process are investigated in warm collisional plasmas. The Compton scattering cross section in warm collisional plasmas is obtained by the Salpeter structure factor with the fluctuation-dissipation theorem and the plasma dielectric function as a function of the electron-neutral collision frequency, Debye length, and wave number. It is shown that the influence of electron-neutral collision strongly suppresses the Compton scattering cross section in warm collisional plasmas. It is also found that the electron-neutral collision effect on the differential Compton scattering cross section is more significant in forward scattering directions. We show that the differential Compton scattering cross section has a maximum at the scattering angle φ=π/2. In addition, we find that the electron-neutral collision effect on the total Compton scattering cross section increases with increasing Debye length and wave number. The variation of the Compton scattering cross section due to the change of collision frequency and plasma parameters is also discussed.

Nonthermal and geometric effects on the symmetric and anti-symmetric surface waves in a Lorentzian dusty plasma slab

The nonthermal and geometric effects on the propagation of the surface dust acoustic waves are investigated in a Lorentzian dusty plasma slab. The symmetric and anti-symmetric dispersion modes of the dust acoustic waves are obtained by the plasma dielectric function with the spectral reflection conditions the slab geometry. The variation of the nonthermal and geometric effects on the symmetric and the anti-symmetric modes of the surface plasma waves is also discussed.

Dielectric function of dense plasmas, their stopping power, and sum rules.

Mathematical, particularly, asymptotic properties of the random-phase approximation, Mermin approximation, and extended Mermin-type approximation of the coupled plasma dielectric function are analyzed within the method of moments. These models are generalized for two-component plasmas. Some drawbacks and advantages of the above models are pointed out. The two-component plasma stopping power is shown to be enhanced with respect to that of the electron fluid.

The loss function of dense plasmas and sum rules

Mathematical, particularly, asymptotic properties of the RPA and RPA with dynamic local field corrections of the coupled plasma dielectric function are analyzed within the method of moments which satisfies some exact relations. Particularly f-sum rule,higher-order sum rules and other conservation laws. Thehigher-order sum rules take into account the correlations in the system under scrutiny, so if the system dynamic characteristics, e.g., the dielectric function, do not satisfy these rules which are effectively additional conservation laws, it is difficultto expect the corresponding model to be adequate in the strong-coupling domain.Some other drawbacks and advantages of the above models are pointed out.

Ion wake formation with dust charge fluctuation in complex plasma

In complex plasma, the interaction mechanism among dust grains near the plasma sheath is significantly influenced by the downward ion flow towards the sheath and dust charge fluctuation over grain surface. Asymmetric ion flow towards the sheath gives rise to well known attractive wake potential in addition to repulsive Yukawa type of potential. The present work shows that the charging dynamics play a significant role in modification of plasma dielectric response function and hence the interaction mechanism among test dust particulates. The effective Debye length is found to be a characteristic of dust size and background plasma response towards the grain along with ion flow speed. The potentials thus obtained show a damping in strength of interaction in the presence of dynamical charging of dust as compared to that of constant charge dust grains. The result also shows decrease in focal length of ion lensing with increase in grain size.

Electron-exchange and quantum screening effects on the Thomson scattering process in quantum Fermi plasmas

The influence of the electron-exchange and quantum screening on the Thomson scattering process is investigated in degenerate quantum Fermi plasmas. The Thomson scattering cross section in quantum plasmas is obtained by the plasma dielectric function and fluctuation-dissipation theorem as a function of the electron-exchange parameter, Fermi energy, plasmon energy, and wave number. It is shown that the electron-exchange effect enhances the Thomson scattering cross section in quantum plasmas. It is also shown that the differential Thomson scattering cross section has a minimum at the scattering angle Θ=π/2. It is also found that the Thomson scattering cross section increases with an increase of the Fermi energy. In addition, the Thomson scattering cross section is found to be decreased with increasing plasmon energy.

Effects of turbulence on the Thomson scattering process in turbulent plasmas by the scattering of electromagnetic waves

The effects of turbulence on the Thomson scattering process are investigated in turbulent plasmas. The Thomson scattering cross section in turbulent plasmas is obtained by the fluctuation-dissipation theorem and plasma dielectric function as a function of the diffusion coefficient, wave number, and Debye length. It is demonstrated that the turbulence effect suppresses the Thomson scattering cross section. It is also shown that the turbulence effect on the Thomson scattering process decreases with increasing thermal energy. The dependence of the wave number on the total Thomson scattering cross section including the turbulent structure factor is also discussed.This paper is dedicated to the late Prof. P. K. Shukla in memory of exciting and stimulating collaborations on effective interaction potentials in various astrophysical and laboratory plasmas.

The Influence of Strong Laser Fields on the Interaction between Fast B+3 Clusters and Plasmas

The influence of a high-intensity laser field on the inelastic interactions between a swift B+3 cluster ion and a plasma target is studied by means of the linearized Vlasov-Poisson theory. Excitations of the plasma are described by the classical plasma dielectric function. In the presence of the laser field, the general expressions for the induced potential in the target and the interaction force among the ions within the cluster are derived. Based on the numerical solution of the equations of motion for the constituent ions, the Coulomb explosion patterns and the cluster's energy losses are discussed for a range of laser parameters.

Quantum and geometric effects on the symmetric and anti-symmetric modes of the surface plasma wave

The propagation of the surface quantum plasma waves is investigated in a thin quantum plasma slab. The symmetric and anti-symmetric dispersion modes of the quantum surface wave are obtained by the plasma dielectric function with the kinetic dispersion model for the slab geometry. The quantum mechanical and slab geometric effects on the symmetric and anti-symmetric modes are also discussed.