Electron Plasma Oscillations Research Articles

Electron densities in the upper ionosphere of Mars from the excitation of electron plasma oscillations

In addition to remote radio sounding of the ionosphere of Mars, the MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) instrument on the Mars Express spacecraft is also able to measure the in situ electron density from the excitation of local electron plasma oscillations. This paper presents an investigation of the electron density in the upper ionosphere of Mars based on the frequency of these oscillations. The advantage of this method is that electron densities can be measured at much higher altitudes than can be determined from remote radio soundings. Using this technique electron densities from 503 orbits have been analyzed over the period from 4 August 2005 to 31 July 2007 for altitudes ranging from about 275 to 1300 km. Although there is considerable variability from orbit to orbit, the median electron density at a given solar zenith angle (SZA) on the dayside of Mars decreases systematically with increasing altitude with a characteristic plasma scale height varying from about 80 to 145 km. At a fixed altitude, the electron density remains almost constant for SZAs less than about 80°. For SZAs greater than about 80° the electron density decreases rapidly with increasing SZA, approaching very low values on the nightside. Simulations performed using both magnetohydrodynamic and hybrid codes show that the nearly constant density at a given altitude is caused by the horizontal transport of plasma from the dayside toward the nightside due to interaction with the solar wind.

Intense plasma waves at and near the solar wind termination shock

Plasma waves are a characteristic feature of shocks in plasmas, and are produced by non-thermal particle distributions that develop in the shock transition layer. The electric fields of these waves have a key role in dissipating energy in the shock and driving the particle distributions back towards thermal equilibrium. Here we report the detection of intense plasma-wave electric fields at the solar wind termination shock. The observations were obtained from the plasma-wave instrument on the Voyager 2 spacecraft. The first evidence of the approach to the shock was the detection of upstream electron plasma oscillations on 1 August 2007 at a heliocentric radial distance of 83.4 au (1 au is the Earth-Sun distance). These narrowband oscillations continued intermittently for about a month until, starting on 31 August 2007 and ending on 1 September 2007, a series of intense bursts of broadband electrostatic waves signalled a series of crossings of the termination shock at a heliocentric radial distance of 83.7 au. The spectrum of these waves is quantitatively similar to those observed at bow shocks upstream of Jupiter, Saturn, Uranus and Neptune.

Changes in the State of Silver Sol Particles after Low-Temperature Treatments

The influence of the low-temperature treatment of Ag hydrosol on the properties of silver particles was studied by electron absorption spectroscopy over the temperature range 77–230 K. Low-temperature treatment caused the aggregation of particles because of an increase in the number of defects on the surface of Ag observed as an increase in the damping coefficient of electron plasma oscillations. These processes depended on the temperature and initial concentration of disperse silver. Defect formation is explained taking into account the tunnel mechanism of the interaction of low-atomic mobile H+(H2O)nand OH-(H2O)nclusters with the surface of silver particles at low temperatures.

Negative refraction with magnetic resonance in a metallic double-ring metamaterial

Metallic metamaterials, by periodically arranged double rings, without splits in both of them, are investigated to show their negative refraction at the magnetically resonant transmission band. It is verified that the negative refraction occurs in the transmission regime where the electric response is attributed to the plasma oscillation of electrons, in analogy to the metallic cut-wire metamaterials, and the magnetic response is originated from antiparallel currents induced resonantly in the neighboring edges of the concentric double rings.

Localized plasmons in quantum plasmas

We consider the nonlinear interactions between finite amplitude electron and ion plasma oscillations in a fermionic quantum plasma. Accounting for the quantum statistical electron pressure and the quantum Bohm potential, we derive a set of coupled nonlinear equations that govern the dynamics of modulated electron plasma oscillations (EPOs) in the presence of the nonlinear ion oscillations (NLIOs). We numerically study stationary solutions of our coupled nonlinear equations. We find that the quantum parameter H (equal to the ratio between the plasmonic and electron Fermi energy densities) introduces new features to the electron density and electric potential humps of localized NLIOs in the absence of EPOs. Furthermore, the nonlinear coupling between the EPOs and NLIOs gives rise to a new class of envelope solitons composed of bell shaped electric field envelope of the EPOs, which are trapped in the electron density hole (and an associated negative oscillatory electric potential) that is produced by the ponderomotive force of the EPOs. The knowledge of the localized plasmonic structures is of immense value for interpreting experimental observations in dense quantum plasmas.

Spin-magnetoplasma waves in a 2D electron system

Oscillations of a 2D electron plasma in a transverse magnetic field have been theoretically studied taking into account spin-orbit interaction. Four branches of spin-plasmon oscillations associated with different selection rules for spin and orbital quantum numbers have been shown to appear at a small plasmon momentum in a semiclassical limit (the Fermi energy is much higher than the Landau quantum). In the quantum case (the filling factor ν is about unity), the number of branches changes from three to six depending on ν value.

Ultrafast Fiske effect in semiconductor superlattices induced by the coupling of electron Bloch oscillations to longitudinal optical phonons and coherent plasmons

We show that resonant coupling of coherent electron Bloch oscillations to longitudinal optical phonons in a wide-miniband semiconductor superlattice induces a unidirectional transient electron current in the system. This effect has a profound analogy to the DC Fiske effect observed when a superconductor Josephson junction or a superfluid weak link is coupled, respectively, to an electromagnetic or acoustic resonator. In the ultrafast Fiske effect, the coupling opens an elastic rectifying channel which exists only during the coherence time of the electron wave packets involved. In the considered ultrafast coupling effect, the longitudinal optical phonons in the superlattice play the role of the resonator coupled to the free damped electron Bloch oscillations, via both their amplitude and phase. We also show that similar unidirectional transient current, but with the opposite sign, is induced by non-resonant coupling of electron Bloch oscillations to coherent electron plasma oscillations. This unidirectional transient current can probably explain the origin, the sign and the carrier-density dependence of the self-induced coherent unidirectional current, which was observed in an undoped biased semiconductor superlattice with photo-excited carriers.

Fluid Turbulence in Quantum Plasmas

Nonlinear fluid simulations are developed by us to investigate the properties of fully developed two-dimensional (2D) electron fluid turbulence in a very dense Fermi (quantum) plasma. We find that a 2D quantum electron plasma exhibits dual cascades, in which the electron number density cascades towards smaller turbulent scales, while the electrostatic potential forms larger scale eddies. The characteristic turbulent spectrum associated with the nonlinear electron plasma oscillations (EPO) is determined critically by a ratio of the energy density of the EPOs and the electron kinetic energy density of quantum plasmas. The turbulent transport corresponding to the large-scale potential distribution is predominant in comparison with the small-scale electron number density variation, a result that is consistent with the classical diffusion theory.

Nonlinear Interactions between Electromagnetic Waves and Electron Plasma Oscillations in Quantum Plasmas

We consider nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and electron plasma oscillations (EPOs) in a dense quantum plasma, taking into account the electron density response in the presence of the relativistic ponderomotive force and mass increase in the CPEM wave fields. The dynamics of the CPEM waves and EPOs is governed by the two coupled nonlinear Schrödinger equations and Poisson's equation. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave pipes in the electron density hole that is associated with a positive potential distribution in our dense plasma. The relevance of our investigation to the next generation intense laser-solid density plasma interaction experiments is discussed.

Amplitude modulation of electron plasma oscillations in a dense electron-hole plasma

By using a quantum hydrodynamic model, the amplitude modulation of electron plasma oscillations (EPOs) in an unmagnetized dense electron-hole (e-h) quantum plasma is investigated. The standard reductive perturbation technique is used to derive one-dimensional nonlinear Schrödinger equation for the modulated EPO wave packet. The effects of the quantum diffraction, charged dust impurities and the effective e-h mass ratio on the propagation of linear dispersive EPOs, as well as on the modulational stability/instability of finite amplitude EPOs are examined. It is found that these parameters significantly affect the propagation of the EPOs as well as the nonlinear stability/instability domain of the wave vector, quite distinct from the classical and quantum electron-ion or electron-positron plasmas. The relevance of our investigation to semiconductor plasmas is discussed.

On the ponderomotive force and the effect of loss reaction on parametric instability

In this paper, the growth rate, ponderomotive force and the exciting condition for parametric instability are derived by considering the loss reaction using a new method. On the basis of the hydrodynamic equations, we take the production and loss reactions in plasma into account to derive the coupling equations for the electron plasma oscillation and ion acoustic oscillation, and obtain the growth rate for the parametric instability, the ponderomotive force and the exciting condition. The result shows that (a) the production reaction has no effect on the parametric instability, and the effect of loss reaction on the parametric instability is a damping one, (b) the more intensive the external field or pump is, the larger the growth rate is, (c) there exist two modes of the ponderomotive force, i.e.the high frequency mode and the low frequency mode, and (d) when ponderomotive force counteracts the damping force, the oscillations become non-damping and non-driving. The ratio of the electron plasma oscillation to ion acoustic oscillation is independent of the loss reaction and the external field.

Phase mixing due to ion motion and relativistic effects in nonlinear plasma oscillations

Nonlinear electron plasma oscillations in a cold-plasma have been studied numerically using one-dimensional (1D) Vlasov–Poisson equations. It is shown that both ion motion and the relativistic effect of electron motion can lead to phase mixing phenomena even if a plasma oscillation is at a moderate amplitude. When its amplitude is relatively small, the phase mixing is mainly caused by the ion motion. When its amplitude is large, the relativistic effect of electrons is dominant. The nonlinear process caused by the relativistic effect depends significantly upon the phase velocity of the plasma oscillation, while that caused by the ion motion depends weakly upon its phase velocity.

Plasma irregularities in unstable outer ionosphere according to the Intercosmos-Bulgaria-1300 satellite data

The results of the satellite low-latitude and mid-latitude measurements of the disturbed plasma concentration, electron temperature, and quasi-stable electric field at heights of ∼900 km after sunset are discussed. It is shown that the sharp fronts of changes in the electron temperature and plasma density observed in the experiment onboard the Intercosmos-Bulgaria-1300 satellite in the low-latitude (and equatorial) outer ionosphere can be related to damping of the oscillations of plasma electrons at local decreases of the plasma density (plasma “pits”) and formation of the vortex plasma structures at density and temperature gradients, which promotes conservation of ionosphere irregularities and makes the fronts of concentration variations steeper. Nonmonotonic variations in the plasma conductivity for the ionosphere currents in unstable plasma can be a cause of observed nonmonotonic disturbances of the vertical component of the “constant” electric field.

The effect of the production and loss reactions on the parametric instability

In this paper, the effect of the loss and production reactions on the parametric instability in plasma is investigated. Based on the hydrodynamic equations, we derive the wave equations for the electron plasma oscillation and ion-acoustic oscillation and obtain the threshold and the growth rate for the parametric instability. It is shown that (1) there is no effect of production reaction on the parametric instability; (2) the effect of loss reaction on the parametric instability is a slight damping; (3) the higher threshold is needed to excite the parametric instability in plasma with the loss reaction; (4) if taking the loss reaction into account, the growth rate for parametric instability will decrease by one half of the loss rate; and (5) the growth rate increases as the external field increases.

Nonlinear transformation of electromagnetic wave in time-varying plasma medium: Longitudinal propagation

The nonlinear transformation of a linearly polarized source plane electromagnetic wave, propagating along an external static magnetic field in free space for t<0, due to the sudden creation of homogeneous plasma at t=0 and sudden switching off the external magnetic field after an elapsed time interval τ, is studied. This transformation has been analyzed by using the second order perturbation theory in radio approximation. For t>τ, the stationary (rectification and space-varying) modes, the electron and electromagnetic plasma oscillations and traveling electron and electromagnetic plasma waves have been created. Among the large variety of nonlinear longitudinal electric modes the appearance of rectification mode was observed. The efficiency of excitation of the longitudinal electric rectification mode has been studied for different values of source wave angular frequency, electron cyclotron angular frequency, and duration time τ of external static magnetic field.

Plasma Instability and Terahertz Generation in HEMTs Due to Electron Transit-Time Effect

We study the coupled spatio-temporal variations of the electron density and the electric field (electron plasma oscillations) in high-electron mobility transistors using the developed device model. The excitation of electron plasma oscillations in the terahertz range of frequencies might lead to the emission of terahertz radiation. In the framework of the model developed, we calculate the resonant plasma frequencies and find the conditions for the plasma oscillations self-excitation (plasma instability) We show that the transit-time effect in the high-electric field region near the drain edge of the channel of high-electron mobility transistors can cause the self-excitation of the plasma oscillations. It is shown that the self-excitation of plasma oscillations is possible when the ratio of the electron velocity in the high field region, u d , and the gate length, Lg, i.e., the inverse transit time are sufficiently large in comparison with the electron collision frequency in the gated channel, v. The transit-time mechanism of plasma instability under consideration can superimpose on the Dyakonov-Shur mechanism predicted previously strongly affecting the conditions of the instability and, hence, terahertz emission. The instability mechanism under consideration might shed light on the origin of terahertz emission from high electron mobility transistors observed in recent experiments.

One-Dimensional Nonlinear and Nonlocal Oscillations of Plasma in Solid Body

A simple one-dimensional model describing nonlinear and nonlocal oscillations of electron plasma is considered. Due to regard of the nonlocality of the field potential, it allows one to smooth down the peaks of nonlinear waves, to steep up the wave front, and to modify the velocity amplitude and phase of the traveling wave.

Stimulated scattering instabilities of electromagnetic waves in an ultracold quantum plasma

The nonlinear interaction between a large-amplitude electromagnetic wave (EMW) and low-frequency electron and ion plasma oscillations in a quantum plasma is considered. By using the Maxwell equations and the quantum hydrodynamic equations, a system of equations, which shows the nonlinear couplings between the EMWs and the electrostatic plasma oscillations, is derived. The nonlinear mode coupled equations are then Fourier analyzed to obtain the dispersion relation which exhibits decay and modulational instabilities. The relevance of such an investigation of stimulated scattering of light off plasmons in ultracold quantum plasmas is noted.

ON THE SURFACE GYROMAGNETIC PLASMONS IN A METAL SPHERE

It is argued that in the long wavelength limit of electromagnetic, far infrared, field optical response of an ultrafine metal particle threaded by uniform magnetic field can be properly modeled by equations of semiclassical electron theory in terms of the surface inertial-wave-like oscillations of free electrons driven by Lorentz restoring force. The detailed calculation of the frequency of size-independent gyromagnetic plasmon resonances computed as a function of multipole degree of electron cyclotron oscillations is presented. This spectrum is derived in juxtaposition with the canonical Mie's spectral formula for the surface plasmon resonances caused by the Coulomb-force-driven plasma oscillations of conduction electrons.

Exact solution of the Landau dispersion equation for electron plasma oscillations

An exact solution of the Landau dispersion equation for Max well electron plasma oscillations has been obtained in the short-wavelength limit krD » 1, where k is the wavenumber and rD is the Debye-Huckel screening radius.