Plasma Wave Dispersion Research Articles

Toward developing a comprehensive algorithm for solving kinetic plasma dispersion relations for parallel propagation with a kappa distribution

In general, it is challenging to numerically solve all the roots of plasma wave dispersion relations. The velocity distributions of multi-component particles in an anisotropic high-energy plasma can be better described by a drift loss-cone bi-Kappa distribution or a mixed drift loss-cone distribution containing bi-Kappa and bi-Maxwellian plasma in space and laboratories. In this work, we have developed a code with a new numerical algorithm to solve all roots of the kinetic dispersion relation for parallel propagation in hot magnetized plasmas with drift loss-cone bi-Kappa distribution. Solving all roots of the rational expansions of the kinetic dispersion relation is equivalent to a matrix eigenvalue problem of a linear system. We have performed detailed numerical solutions for three kinds of plasmas: bi-Maxwellian, bi-Kappa, and cold plasmas. We have also proposed a unified numerical method to solve the mixed dispersion relation based on the bi-Kappa and bi-Maxwellian distributions. The numerical results and benchmark studies demonstrate that the new algorithm is in agreement with the data from previous studies. This is a crucial step toward revealing a full picture of kinetic plasma waves and instabilities.

Collective phenomena in a quasi-classical electron fluid within the interpolational self-consistent method of moments

Collective processes in a quasi-classical electron gas are investigated within the framework of the interpolational self-consistent method of moments, which makes it possible to express the dispersion and decrement of plasma waves, and the dynamic structural factor of the system exclusively in terms of its static structural factor so that five sum rules are satisfied automatically. Different models are used of the static structure factor; the stability and robustness of the results of the moment approach taking into account the accuracy of these models is confirmed and tested by comparison to the alternative molecular dynamics simulation data.

First Intrashot Observation of Runaway-Electron-Driven Instabilities at the Lower-Hybrid Frequency Range under ITER-Relevant Plasma-Wave Dispersion Conditions.

Kinetic instabilities driven by runaway electrons (REs) have recently received attention in the fusion community as a means to control and diagnose REs in a tokamak. Experiments aimed at studying such kinetic instabilities have been performed at the Frascati Tokamak Upgrade (FTU), where different families of waves have been identified, from wide-band bursting emissions to quasi-monochromatic waves and sharp lines, in the presence of REs with energies from a few to tens of MeV. A specific family of waves with intense kinetic drive was directly observed for the first time, during both the early Ohmic plasma start-up and the current ramp-up. A clear wave frequency scaling with respect to the electron density was demonstrated. This scaling, with the complementary analysis of signals observed at different magnetic fields, allowed the identification of these instabilities as lower-hybrid waves. The relevant analysis shown in this Letter is based on a continuous intrashot detection of the RE-driven wave, which is reported for the first time for this kind of instability. We demonstrated that unstable waves are excited already at the very beginning of a tokamak discharge, opening the way to new possible research on the exploitation of this kind of measurement for monitoring seed REs formation at the early plasma stage, while most diagnostics still have limited capabilities. The conditions for plasma wave dispersion at the early phase of the FTU discharge are very similar to the ones expected during the ITER start-up, when analogous instabilities might, hence, come to light, in case of formation of suprathermal populations.

Determining EMIC Wave Vector Properties Through Multi-Point Measurements: The Wave Curl Analysis.

Electromagnetic ion cyclotron (EMIC) waves play important roles in particle loss processes in the magnetosphere. Determining the evolution of EMIC waves as they propagate and how this evolution affects wave‐particle interactions requires accurate knowledge of the wave vector, k. We present a technique using the curl of the wave magnetic field to determine k observationally, enabled by the unique configuration and instrumentation of the Magnetospheric MultiScale (MMS) spacecraft. The wave curl analysis is demonstrated for synthetic arbitrary electromagnetic waves with varying properties typical of observed EMIC waves. The method is also applied to an EMIC wave interval observed by MMS on October 28, 2015. The derived wave properties and k from the wave curl analysis for the observed EMIC wave are compared with the Waves in Homogenous, Anisotropic, Multi‐component Plasma (WHAMP) wave dispersion solution and with results from other single‐ and multi‐spacecraft techniques. We find good agreement between k from the wave curl analysis, k determined from other observational techniques, and k determined from WHAMP. Additionally, the variation of k due to the time and frequency intervals used in the wave curl analysis is explored. This exploration demonstrates that the method is robust when applied to a wave containing at least 3–4 wave periods and over a rather wide frequency range encompassing the peak wave emission. These results provide confidence that we are able to directly determine the wave vector properties using this multi‐spacecraft method implementation, enabling systematic studies of EMIC wave k properties with MMS.

Influence of nonlinear detuning at plasma wavebreaking threshold on backward Raman compression of non-relativistic laser pulses

Taking into account the nonlinear dispersion of the plasma wave, the fluid equations for the three-wave (Raman) interaction in plasmas are derived. It is found that, in some parameter regimes, the nonlinear detuning resulting from the plasma wave dispersion during Raman compression limits the plasma wave amplitude to noticeably below the generally recognized wavebreaking threshold. Particle-in-cell simulations confirm the theoretical estimates. For weakly nonlinear dispersion, the detuning effect can be counteracted by pump chirping or, equivalently, by upshifting slightly the pump frequency, so that the frequency-upshifted pump interacts with the seed at the point where the plasma wave enters the nonlinear stage.

Photon polarizability and its effect on the dispersion of plasma waves

High-frequency photons travelling in plasma exhibit a linear polarizability that can influence the dispersion of linear plasma waves. We present a detailed calculation of this effect for Langmuir waves as a characteristic example. Two alternative formulations are given. In the first formulation, we calculate the modified dispersion of Langmuir waves by solving the governing equations for the electron fluid, where the photon contribution enters as a ponderomotive force. In the second formulation, we provide a derivation based on the photon polarizability. Then, the calculation of ponderomotive forces is not needed, and the result is more general.

Estimation of HF artificial ionospheric turbulence characteristics using comparison of calculated plasma wave decay rates with the measured decay rates of the stimulated electromagnetic emission

It is shown experimentally that the relaxation time of the stimulated electromagnetic emission (SEE) after the pump wave turn off decreases when frequency of the electromagnetic wave, responsible for the SEE generation (pump wave f0 or diagnostic wave fdw) approaches 4th harmonic of the electron cyclotron frequency fce. Since the SEE relaxation is determined by the damping rate of plasma waves with the same frequency, responsible for the SEE generation, we calculated damping rates of plasma waves with ω∼ωuh (ω is the plasma wave frequency, ωuh is the upper hybrid frequency) for frequencies close to and distant from the double resonance where ωuh∼4ωce (ωce=2πfce). The calculations were performed numerically on the base of linear plasma wave dispersion relation at arbitrary ratio between |Δ|=ω-4ωce and |k‖|VTe (VTe is the electron thermal speed and k‖ is the projection of the wave vector onto the magnetic field direction. A comparison of calculation and experimental results has shown that obtained frequency dependence of the SEE decay rate is similar to the damping rate frequency dependence for plasma waves with wave vectors directed at the angles 60–70° to the magnetic field, and gives a strong hint that oblique upper hybrid plasma waves should be responsible for the SEE generation.

Hot plasma modes across Reissner–Nördstrom–de Sitter horizon in a Veselago medium

We investigate wave attributes of hot plasma around a Reissner–Nördstrom–de Sitter (RN-dS) metric in a Veselago medium. A perturbation scheme is implemented on general relativistic magnetohydrodynamical (GRMHD) equations that are further used for Fourier analysis. The linearly perturbed Fourier-analyzed GRMHD equations depict the dispersion of hot plasma waves. It is found that inclusion of charge in de Sitter space greatly affects the wave dispersion. A comparison of wave properties is presented, and results reassert the presence of the Veselago medium.

Intensity dependence of non-linear kinetic behaviour of stimulated Raman scattering in fusion relevant plasmas

Influence of kinetic effects on 3-wave interaction was examined within the frame of stimulated Raman backward scattering (SRBS) in a rarefied laser corona. The plasma is supposed to be weakly collisional with a negligible density gradient. The model is centred on the physical situation of shock ignition at a large scale direct drive compression experiments. The modelling uses a 1D geometry in a Maxwell-Vlasov model. The method used is a truncated Fourier-Hermite expansion numerically stabilized by a model collisional term with a realistic value of the collision frequency. In parallel, besides the linear theory of SRBS, a coupled mode 3-wave equation system (laser driving wave, Raman back-scattered wave and the daughter forward scattered plasma wave) is solved to demonstrate the correspondence between the full kinetic model and 3-wave interaction with no electron kinetics involved to identify the differences between both the solutions arising due to the electron kinetic effects. We concentrated mainly on the Raman reflectivity, which is one of the important parameters controlling the efficiency of the shock ignition scheme. It was found that the onset of the kinetic effects has a distinct intensity threshold, above which the Raman reflectivity may go down due to the electron kinetics. In addition, we were trying to identify the most important features of the electron phase space behaviour, such as particle trapping in potential minima of the generated plasma wave and its consequences for the 3-wave interaction. The role of the trapped electrons seems to be crucial for a deformation of the plasma wave dispersion curve, as indicated in some earlier work.

Electrostatic waves in plasma: the case of an expanding microwave plasma sustained in argon

This work is devoted to the study of the electrostatic wave dispersion in plasma. Investigations are focused on waves with angular frequency ranging between the ion and the electron angular resonance frequency. The dispersion equation is resolved by means of a Fourier transform spectral method in the case of theoretical Maxwell–Boltzmann electron energy distribution functions (EEDFs), and in the case of experimental EEDFs measured by means of a Langmuir probe in microwave expanding plasma sustained in argon. The results show the change of the dispersion curve with the plasma parameters and the role of electrons and ions in the shape of the dispersion curve.

Semiconductor nanotube plasma

The theory of dispersion of surface plasma waves in semiconductor nanotubes is presented. The effect of screening the Coulomb field of a static point charge by a magnetized electron gas of a nanotube is investigated. The main properties of the semiconductor nanotube plasma, 3D plasma, and planar 2D plasma are compared. The dependences of the critical temperature and thermodynamic properties of a superconducting quantum cylinder on the characteristics of the system are studied.

Reduction of angular dip width of surface plasmon resonance sensor by coupling surface plasma waves on sensing surface and inside metal–dielectric–metal structure

A surface plasmon resonance (SPR) scheme was developed using a metal/dielectric/metal (MDM) structure. The surface plasma wave (SPW) dispersion curves within the MDM structure can be controlled by tuning the dielectric layer thickness. Therefore, the properties of the SPWs on the sensing surface of the SPR sensor can be tuned by coupling the tunable odd SPWs in the MDM structure to the sensing SPWs. The proposed tuning procedure was based on the tendency for anticrossing formation to occur between two nonparallel dispersion curves, and the reduction in the angular dip widths of the SPR sensors using the proposed procedure was demonstrated both numerically and experimentally.

Dispersion of low frequency plasma waves upstream of the quasi-perpendicular terrestrial bow shock

Abstract. Low frequency waves in the foot of a supercritical quasi-perpendicular shock front have been observed since the very early in situ observations of the terrestrial bow shock (Guha et al., 1972). The great attention that has been devoted to these type of waves since the first observations is explained by the key role attributed to them in the processes of energy redistribution in the shock front by various theoretical models. In some models, these waves play the role of the intermediator between the ions and electrons. It is assumed that they are generated by plasma instability that exist due to the counter-streaming flows of incident and reflected ions. In the second type of models, these waves result from the evolution of the shock front itself in the quasi-periodic process of steepening and overturning of the magnetic ramp. However, the range of the observed frequencies in the spacecraft frame are not enough to distinguish the origin of the observed waves. It also requires the determination of the wave vectors and the plasma frame frequencies. Multipoint measurements within the wave coherence length are needed for an ambiguous determination of the wave vectors. In the main multi-point missions such as ISEE, AMPTE, Cluster and THEMIS, the spacecraft separation is too large for such a wave vector determination and therefore only very few case studies are published (mainly for AMPTE UKS AMPTE IRM pair). Here we present the observations of upstream low frequency waves by the Cluster spacecraft which took place on 19 February 2002. The spacecraft separation during the crossing of the bow shock was small enough to determine the wave vectors and allowed the identification of the plasma wave dispersion relation for the observed waves. Presented results are compared with whistler wave dispersion and it is shown that contrary to previous studies based on the AMPTE data, the phase velocity in the shock frame is directed downstream. The consequences of this finding for both types of models that were developed to explain the generation of these waves are discussed.

Plasma waves in a superlattice based on graphene

The law of plasma wave dispersion in an electron gas in a superlattice based on graphene on a striped substrate is studied numerically. Calculations are performed based on the quantum theory of plasma waves in the approximation of random phases with allowance for umklapp processes. The estimated plasmon frequencies for the graphene-based superlattices on striped substrates now under theoretical study is ω ≤ 1014 s−1.

Effects of Rotating Nanoparticles on the Instability of Dust-Acoustic Waves in a Plasma Containing Superthermal Electrons and Ions

Charged particles with sizes ranging from tens of nanometer to tens of micrometer are created in various situations such as DC discharges, rf discharges, laser-driven plasmas, processing plasmas used in device fabrications, as well as in space such as interstellar clouds, solar system, etc. In general, a large number of background electrons could stick onto the nanoparticle surface during the charging processes and as a result a significant depletion of the electron number density can be encountered. If charged non-spherical nanoparticles are created, they can rotate due to the interaction with surrounding plasmas or oscillating electric field. Therefore, a significant modification of the conventional plasma wave dispersion relations might be necessary for the complex plasma that consists of electrons, ions and nanoparticles. In this work, the growing of dust-acoustic wave is investigated in the presence of the nanoparticles in a superthermal plasma. Full spectrums of the growth rate of the dust-acoustic wave is obtained and analyzed to investigate the effect of nanoparticle rotation. The superthermal plasma effect on the growth rate is also analyzed. The growth rate was found to be enhanced by the rotation of nanoparticles, but suppressed by the superthermal plasmas.

Multiple harmonic ULF waves in the plasma sheet boundary layer: Instability analysis

Multiple‐harmonic electromagnetic waves in the ULF band have occasionally been observed in Earth's magnetosphere, both near the magnetic equator in the outer plasmasphere and in the plasma sheet boundary layer (PSBL) in Earth's magnetotail. Observations by the Cluster spacecraft of multiple‐harmonic electromagnetic waves with fundamental frequency near the local proton cyclotron frequency, Ωcp, were recently reported in the plasma sheet boundary layer by Broughton et al. (2008). A companion paper surveys the entire magnetotail passage of Cluster during 2003, and reports 35 such events, all in the PSBL, and all associated with elevated fluxes of counterstreaming ions and electrons. In this study we use observed pitch angle distributions of ions and electrons during a wave event observed by Cluster on 9 September 2003 to perform an instability analysis. We use a semiautomatic procedure for developing model distributions composed of bi‐Maxwellian components that minimizes the difference between modeled and observed distribution functions. Analysis of wave instability using the WHAMP electromagnetic plasma wave dispersion code and these model distributions reveals an instability near Ωcp and its harmonics. The observed and model ion distributions exhibit both beam‐like and ring‐like features which might lead to instability. Further instability analysis with simple beam‐like and ring‐like model distribution functions indicates that the instability is due to the ring‐like feature. Our analysis indicates that this instability persists over an enormous range in the effective ion beta (based on a best fit for the observed distribution function using a single Maxwellian distribution), β′, but that the character of the instability changes with β′. For β′ of order unity (for instance, the observed case with β′ ∼ 0.4), the instability is predominantly electromagnetic; the fluctuating magnetic field has components in both the perpendicular and parallel directions, but the perpendicular fluctuations are larger. If β′ is greatly decreased to about 5 × 10−4 (by increasing the magnetic field), the instability becomes electrostatic. On the other hand, if β′ is increased (by decreasing the magnetic field), the instability remains electromagnetic, but becomes predominantly compressional (magnetic fluctuations predominantly parallel) at β′ ∼ 2. The β′ dependence we observe here may connect various waves at harmonics of the proton gyrofrequency found in different regions of space.

Short-wavelength plasmons in low-dimensional systems

The dispersion of plasma waves in systems of various dimensions is investigated up to the end point of the spectrum. In 2D and 3D systems, the plasmon spectrum still ends (due to Landau damping) within the applicability range of the quasi-classical approximation, i.e., for ħk ≪ pF (ħk is the plasmon momentum and pF is the electron Fermi momentum). In 1D systems, the results are qualitatively different, since the Landau damping is concentrated in a region where the quantum effects cannot be ignored. This peculiarity of 1D systems gives rise to undamped branches of acoustic plasmons with a phase velocity lower than the electron Fermi velocity in multicomponent 1D plasmas.

Electrical excitation of shock and soliton‐like waves in high‐electron‐mobility transistor structures

AbstractAbstract

Tunable plasma wave resonant detection of optical beating in high electron mobility transistor

The authors report on tunable terahertz resonant detection of two 1.55μm cw lasers beating by plasma waves in AlGaAs∕InGaAs∕InP high electron mobility transistor. The authors show that the fundamental plasma resonant frequency and its odd harmonics can be tuned with the applied gate voltage in the range of 75–490GHz. The observed frequency dependence on gate bias is found to be in good agreement with the theoretical plasma wave dispersion law.

Nonlinear Guiding Center Theory of Perpendicular Diffusion in Dynamical Turbulence

Recently, a nonlinear theory for perpendicular diffusion of charged particles was presented by Matthaeus and coworkers. This theory is called the Nonlinear Guiding Center (NLGC) theory and provides an integral equation for the perpendicular mean free path. In this paper we consider numerical results of this equation in the case of dynamical turbulence. We consider solutions for two prominent models for dynamical turbulence: the damping model of dynamical turbulence and the random sweeping model. For both models we also use a general power spectrum with an energy, inertial, and dissipation range. In the current paper we also examine the NLGC theory for two different plasma wave dispersion relations, shear Alfven waves and fast magnetosonic waves. We compare all these numerical results with observational results and with solutions of the magnetostatic dissipationless NLGC theory.