Yu. Tyshetskiy

Surface plasmon polaritons in a semi-bounded degenerate plasma: Role of spatial dispersion and collisions

Surface plasmon polaritons (SPPs) in a semi-bounded degenerate plasma (e.g., a metal) are studied using the quasiclassical mean-field kinetic model, taking into account the spatial dispersion of the plasma (due to quantum degeneracy of electrons) and electron-ion (electron-lattice, for metals) collisions. SPP dispersion and damping are obtained in both retarded (ω/kz∼c) and non-retarded (ω/kz≪c) regions, as well as in between. It is shown that the plasma spatial dispersion significantly affects the properties of SPPs, especially at short wavelengths (less than the collisionless skin depth, λ ≲ c/ωpe). Namely, the collisionless (Landau) damping of SPPs (due to spatial dispersion) is comparable to the purely collisional (Ohmic) damping (due to electron-lattice collisions) in a wide range of SPP wavelengths, e.g., from λ∼20 nm to λ∼0.8 nm for SPP in gold at T = 293 K and from λ∼400 nm to λ∼0.7 nm for SPPs in gold at T = 100 K. The spatial dispersion is also shown to affect, in a qualitative way, the dispersi...

High-frequency electromagnetic surface waves in a semi-bounded weakly ionized plasma

High-frequency electromagnetic surface waves (SWs) in a weakly ionized plasma half-space with Maxwellian electrons are studied taking into account elastic electron-neutral collisions. The SWs spectrum and damping rate are obtained numerically for a wide range of wavelengths, and the asymptotes of damping rate are analytically calculated in some limits. It is shown that the high-frequency SWs become strongly damped at wavelengths λ<λMin, where λMin significantly depends on plasma parameters (e.g., electron temperature and electron and neutral atom density). The relative importance of collisional and Cherenkov (collisionless) damping of SWs is investigated and is graphically shown for a range of plasma parameters and SW wavelengths. The behavior of weakly ionized plasma with respect to the SW propagation has been recovered for the collisional parameter η.

Dispersion and damping of potential surface waves in a degenerate plasma

Potential (electrostatic) surface waves (SWs) in a semi-bounded plasma with degenerate electrons are studied using the quasi-classical mean-field kinetic model. The SW spectrum and the collisionless damping rate are obtained numerically for a wide range of wavelengths. In the limit of long wavelengths, the SW frequency ω approaches the cold-plasma limit ω=ωp/2 with ωp being the plasma frequency, while at short wavelengths, the SW spectrum asymptotically approaches the spectrum of zero-sound mode propagating along the boundary. It is shown that the surface waves in this system remain weakly damped at all wavelengths (in contrast to strongly damped surface waves in Maxwellian electron plasmas), and the damping rate nonmonotonically depends on the wavelength, with the maximum (yet small) damping occurring for surface waves with wavelength of ≈5πλF, where λF is the Thomas-Fermi length. The applicability of the used approximations and of the obtained results is discussed in detail.

A new type of surface waves in a fully degenerate quantum plasma

We study the response of a semi-bounded one-component fully degenerate electron plasma to an initial perturbation, in the electrostatic limit. We show that the part of the electric potential corresponding to surface waves in such plasma can be represented, at large times, as the sum of two terms, one term corresponding to “conventional” (Langmuir) surface waves and the other term representing a new type of surface waves resulting from specific analytic properties of degenerate plasmas dielectric response function. These two terms are characterized by different oscillation frequencies (for a given wave number), and while the “conventional” terms amplitude decays exponentially with time, the new term is characterized by a slower, power-law decay of the oscillation amplitude and is therefore dominant at large times.

Statistics of beam-driven waves in plasmas with ambient fluctuations: Reduced-parameter approach

A reduced-parameter (RP) model of quasilinear wave-plasma interactions is used to analyze statistical properties of beam-driven waves in plasmas with ambient density fluctuations. The probability distribution of wave energies in such a system is shown to have a relatively narrow peak just above the thermal wave level, and a power-law tail at high energies, the latter becoming progressively more evident for increasing characteristic amplitude of the ambient fluctuations. To better understand the physics behind these statistical features of the waves, a simplified model of stochastically driven thermal waves is developed on the basis of the RP model. An approximate analytic solution for stationary statistical distribution of wave energies W is constructed, showing a good agreement with that of the original RP model. The “peak” and “tail” features of the wave energy distribution are shown to be a result of contributions of two groups of wave clumps: those subject to either very slow or very fast random varia...

Spatiotemporal correlation functions in beam-driven plasmas with fluctuations

Using a reduced-parameter model of wave-particle interactions in a beam-driven plasma, the linear spatiotemporal correlation functions of wave and particle quantities are derived. These are found to have an oscillatory structure with characteristic spatial and temporal scales reflecting the dynamics of energy exchange between particles and waves. The effects of various system parameters on these characteristic scales and the correlation functions are investigated. The correlation scales are shown to diverge in some limiting cases, implying the possibility of criticality in the system. A comparison with fully nonlinear numerical simulations is carried out, and the criterion for validity of the linear correlation functions is derived and verified. The nonlinear simulation results are shown to converge to the linear prediction in appropriate limits dictated by this criterion. The correlation functions obtained provide a useful tool for studying dynamical properties of beam-driven plasma-wave systems with flu...

Propagation of radiation in fluctuating multiscale plasmas. II. Kinetic simulations

A numerical algorithm is developed and tested that implements the kinetic treatment of electromagnetic radiation propagating through plasmas whose properties have small scale fluctuations, which was developed in a companion paper. This method incorporates the effects of refraction, damping, mode structure, and other aspects of large-scale propagation of electromagnetic waves on the distribution function of quanta in position and wave vector, with small-scale effects of nonuniformities, including scattering and mode conversion approximated as causing drift and diffusion in wave vector. Numerical solution of the kinetic equation yields the distribution function of radiation quanta in space, time, and wave vector. Simulations verify the convergence, accuracy, and speed of the methods used to treat each term in the equation. The simulations also illustrate the main physical effects and place the results in a form that can be used in future applications.

Propagation of radiation in fluctuating multiscale plasmas. I. Kinetic theory

A theory for propagation of radiation in a large scale plasma with small scale fluctuations is developed using a kinetic description in terms of the probability distribution function of the radiation in space, time, and wavevector space. Large scale effects associated with spatial variations in the plasma density and refractive index of the plasma wave modes and small scale effects such as scattering of radiation by density clumps in fluctuating plasma, spontaneous emission, damping, and mode conversion are included in a multiscale kinetic description of the radiation. Expressions for the Stokes parameters in terms of the probability distribution function of the radiation are used to enable radiation properties such as intensity and polarization to be calculated.

Modulational and filamentational instabilities of a monochromatic Langmuir pump wave in quantum plasmas

The modulational and filamentational instabilities of a monochromatic Langmuir pump wave are investigated for the case of collisionless quantum plasmas, using renormalized quantum linear and nonlinear plasma polarization responses. We obtain the quantum-corrected dispersion equation for the modulational and filamentational instabilities growth rates. It is demonstrated that the quantum effect suppresses the growth rates of the modulational and filamentational instabilities.

Potential surface waves on a semibounded degenerate electron plasma: Dispersion and damping

Summary form only given. Linear properties of potential (electrostatic) surface waves (SW) in a semi-bounded collisionless plasma with degenerate electrons are studied by solving the initial-value problem within quasi-classical mean-field kinetic model, taking into account the Pauli exclusion principle for the electrons at equilibrium. The SW spectrum and collisionless damping rate are obtained numerically for a wide range of wavelengths. It is found that at long wavelengths, the SW frequency ω approaches the well-known cold-plasma limit ω = ω p /√2, where ω p is the plasma frequency, while at short wavelengths the SW spectrum approaches the spectrum of the volume zero-sound mode propagating parallel to the boundary. Most importantly, it is shown that the potential surface waves in this system with degenerate electrons remain weakly damped at all wavelengths, in contrast with the strongly damped surface waves in the corresponding system with Maxwellian electrons. Interestingly, the obtained collisionless damping rate has a non-monotonic dependence on the SW wavelength λ, with the maximum damping occurring for waves with λ~5πλ F , where λ F is the electron Thomas-Fermi length.