Low-frequency Electrostatic Waves Research Articles

Linear coupling of Alfven waves and acoustic-type modes in dense quantum magnetoplasmas

A coupled dispersion relation of low frequency shear Alfven waves and electrostatic waves in a dense quantum magnetoplasma is derived by using hydrodynamic model. The dispersive contribution of electron quantum effects is discussed for dynamic as well as static ions. The dominant role of electron Fermi pressure is highlighted and its comparison with the quantum pressure arising due to quantum Bohm potential is presented. For illustrative purpose, the results are analyzed numerically. The relevance of present work with the dense astrophysical and laboratory plasmas is pointed out with possible consequences.

Dust-acoustic wave modulation in the presence of superthermal ions

A study is presented of the nonlinear self-modulation of low-frequency electrostatic (dust acoustic) waves propagating in a dusty plasma, in the presence of a superthermal ion (and Maxwellian electron) background. A kappa-type superthermal distribution is assumed for the ion component, accounting for an arbitrary deviation from Maxwellian equilibrium, parametrized via a real parameter κ. The ordinary Maxwellian-background case is recovered for κ→∞. By employing a multiple scales technique, a nonlinear Schrödinger-type equation (NLSE) is derived for the electric potential wave amplitude. Both dispersion and nonlinearity coefficients of the NLSE are explicit functions of the carrier wavenumber and of relevant physical parameters (background species density and temperature, as well as nonthermality, via κ). The influence of plasma background superthermality on the growth rate of the modulational instability is discussed. The superthermal feature appears to control the occurrence of modulational instability, since the instability window is strongly modified. Localized wavepackets in the form of either bright-or dark-type envelope solitons, modeling envelope pulses or electric potential holes (voids), respectively, may occur. A parametric investigation indicates that the structural characteristics of these envelope excitations (width, amplitude) are affected by superthermality, as well as by relevant plasma parameters (dust concentration, ion temperature).

Dispersion properties of low-frequency electrostatic oscillations in metallic carbon nanotubes

Dispersion properties of low-frequency electrostatic waves in metallic carbon nanotubes (CNTs) are investigated. We assume that metallic CNTs are charged due to the field emission, and hence the metallic nanotubes can be regarded as charged dust rods surrounded by degenerate electrons and ions. We deduce the perturbed electron and ion number densities by using the quantum hydrodynamic model, while the dust rod density perturbation follows the classical expression. The Poisson equation, in turn, gives the dispersion relation for the low-frequency electrostatic oscillations in our three-species bounded plasma system composed of metallic CNTs. The oscillation frequency of CNTs can be used for diagnostic purposes, e.g. for the determination of charge on nanotubes.

Electrostatic solitary waves in a magnetized dusty plasma

The nonlinear evolution of driven low-frequency electrostatic waves is investigated in a three-component magnetized dusty plasma comprised of a warm dust fluid, electrons, and ions. Electrons as well as ions are considered to have Boltzmann distributions. The fluid equations for the dust along with the quasineutrality condition are used to obtain a single nonlinear differential equation for the electric field. Periodic solutions of the nonlinear differential equation yield sinusoidal, sawtooth and bipolar structures which are similar to nonlinear structures supported in electron-ion plasmas. Results of our findings are applied to Saturn’s rings.

Proparyation of Low frequency microwave in dusty Plasma

The numerical simulation for the low frequency waves in dusty plasma has been studied. The studying was done by taking two special cases depending on the direction of the propagation of the wave:First, when the propagation is parallel to the magnetic field K//B,this mode is called acoustic mode.Second,when K B this mode is called cyclotron mode.In addition, every one of the two modes divided into two modes depending on the range of the frequency.The Coulomb coupling parameter was studied, with temperature T,density of the dust particles Nd ,and the charge of the particle Qd.The low frequency electrostatic waves in dusty grains were studied. Also, the properties of ion-acoustic waves and ion-cyclotron waves are shown to modify even through the dust grains do not participate in the wave dynamics. If the dust dynamics induced in the analysis, new “ dust modes “ appear.

Proparyation of Low frequency microwave in dusty Plasma

The numerical simulation for the low frequency waves in dusty plasma has been studied. The studying was done by taking two special cases depending on the direction of the propagation of the wave:First, when the propagation is parallel to the magnetic field K//B,this mode is called acoustic mode.Second,when K B this mode is called cyclotron mode.In addition, every one of the two modes divided into two modes depending on the range of the frequency.The Coulomb coupling parameter was studied, with temperature T,density of the dust particles Nd ,and the charge of the particle Qd.The low frequency electrostatic waves in dusty grains were studied. Also, the properties of ion-acoustic waves and ion-cyclotron waves are shown to modify even through the dust grains do not participate in the wave dynamics. If the dust dynamics induced in the analysis, new “ dust modes “ appear.

Modulation instability of low-frequency electrostatic ion waves in magnetized electron-positron-ion plasma

The nonlinear amplitude modulation of low-frequency electrostatic ion waves propagating in collisionless magnetized electron-positron-ion plasma are studied. The Krylov–Bogoliubov–Mitropolsky perturbation method is employed to derive the nonlinear Schrödinger equation. Modulation instability of both ion-acoustic and ion-cyclotronlike modes is examined. We found that the ion-acoustic mode, which propagates below the ion-cyclotron frequency, is stable if the strength of the external magnetic field is small. However, as the strength of the magnetic field increases, this mode becomes modulationally unstable for a range of wave numbers and angles of propagation. This range increases as the strength of the magnetic field and/or positron density increases. For the ion-cyclotronlike mode, which propagates above the ion-cyclotron frequency, a number of stability/instability regions appear in the (kc,θ) plane even for a very small value of the magnetic field. It is found that, for both modes, critical wave number kc separating the stability and instability regions, shifts towards higher values as the density of the positron increases.

Generation of low-frequency electrostatic and electromagnetic waves as nonlinear consequences of beam–plasma interactions

Nonlinear evolution of the electron two-stream instability in a current-carrying plasma is examined by using a two-dimensional electromagnetic particle-in-cell simulation. Formation of electron phase-space holes is observed as an early nonlinear consequence of electron–beam–plasma interactions. Lower-hybrid waves, electrostatic, and electromagnetic whistler mode waves are also excited by different mechanisms during the ensuing nonlinear wave–particle interactions. It is shown by the present computer simulation with a large simulation domain and a long simulation time that these low-frequency waves can disturb the electrostatic equilibrium of electron phase-space holes, suggesting that the lifetime of electron phase-space holes sometimes becomes shorter in a current-carrying plasma.

A note on the formation of large-scale structures in the Universe

A general dispersion relation for low-frequency electrostatic waves in a self-gravitating pair ion–dust plasma is derived. The dispersion relation admits two classes of the Jeans instability. The growth rates and thresholds of the latter are obtained. The implication of the present work to the formation of large-scale structures in the dusty universe is highlighted.

Low frequency electrostatic waves in weakly inhomogeneous magnetoplasma modeled by Lorentzian (kappa) distributions

Linear dispersion relations for electrostatic waves in spatially inhomogeneous, current-carrying anisotropic plasma, where the equilibrium particle velocity distributions are modeled by various Lorentzian (kappa) distributions and by well-known bi-Maxwellian distribution, are presented. Spatial inhomogeneities, assumed to be weak, include density gradients, temperature gradients, and gradients (shear) in the parallel (to the ambient magnetic field) flow velocities associated with the current. In order to illustrate the distinguishing features of the kappa distributions, stability properties of the low frequency (lower than ion cyclotron frequency) and long perpendicular wavelength (longer than ion gyroradius) modes are studied in detail, and the results are contrasted with those for the bi-Maxwellian distribution. Specific attention is given to the drift waves, the current-driven ion-acoustic waves in the presence of velocity shear, the velocity shear-driven ion-acoustic modes, and the ion temperature-gradient driven modes. Growth rates of the drift wave instability and the current-driven ion-acoustic instability are reduced from their values for bi-Maxwellian distribution due to larger ion Landau damping rates associated with the kappa distributions. For the same reason, excitation conditions for these two instabilities are more stringent in the case of the kappa distributions. Growth rates of the velocity shear-driven ion-acoustic instability and the ion temperature-gradient driven instability are reduced from their values for bi-Maxwellian distribution as a consequence of the reduced adiabatic response of the electrons to the electrostatic potential perturbation. Frequencies of the drift waves and the ion-acoustic waves are also reduced in kappa-distribution plasmas due to the reduced adiabatic response of the electrons.

Linear and nonlinear low-frequency electrostatic waves in a nonuniform pair-ion-dust magnetoplasma

Linear and nonlinear properties of the low-frequency (in comparison with the ion gyrofrequency) electrostatic oscillations in pair-ion-dust magnetoplasma are presented. In the linear limit, the Shukla–Varma mode is coupled with the ion oscillations while the nonlinearly coupled modes appear in the form of a dipolar or a monopolar vortex.

Parallel velocity shear driven electrostatic waves in a very dense nonuniform magnetoplasma

It is shown that the parallel (magnetic field-aligned) velocity shear can drive the low-frequency (in comparison with the ion gyrofrequency) electrostatic (LF-ES) waves in an ultracold super-dense nonuniform magnetoplasma. By using an electron density response arising from the balance between the electrostatic and quantum Bohm forces, as well as the ion density response deduced from the continuity and momentum equations, a wave equation for the LF-ES waves is derived. In the local approximation, a new dispersion relation is obtained by Fourier transforming the wave equation. The dispersion relation reveals an oscillatory instability of dispersive drift-like modes in super-dense quantum magnetoplasmas.

Current driven low-frequency electrostatic waves in the solar corona: Linear theory and nonlinear saturation

Important solar physical problems such as the heating of the corona, reconnection, and electron acceleration might be related to current-driven plasma waves, especially at low frequencies, where, perhaps, most of the wave power is concentrated. Since a direct observation of plasma waves in the solar corona is impossible, theoretical investigations are needed to clarify the possibilities of their excitation, of their nonlinear evolution, and the possible macroscopic consequences of such waves. A multifluid linear dispersion analysis of current flows parallel to the magnetic field in the solar corona is carried out. For this reason, an appropriate linear dispersion solver is developed, considering all possible propagation directions of the waves with respect to the solar magnetic field. As for the assumed plasma model, an electron distribution drifting in the direction parallel to the ambient magnetic field while the background protons were at rest was considered. Thermal effects are taken into account by means of appropriate energy equations of state. Due to their importance for the heating and anomalous transport in the solar corona, the analysis of low-frequency electrostatic waves is studied. For the limiting cases of parallel and perpendicular propagation, the Buneman and the lower-hybrid waves due to a modified two-stream instability were recovered, respectively. For realistic coronal plasma parameters of the lower corona, the dispersion curves of the two basic unstable wave modes are found to approach each other very closely, and their possible nonlinear saturation level is estimated. It appeared that for solar conditions, the two basic modes contribute a comparable (within an order of magnitude) amount of anomalous dissipation, which is quantified by estimating an “effective collision rate.”

Symmetry analysis and similarity electrostatic waves in a nonuniform dusty magnetoplasma

We apply the group theory to a (3+1)-dimensional nonlinear system relevant for the low-frequency electrostatic waves in a nonuniform dusty magnetoplasma. In correspondence with the generators of the symmetry group allowed by the system, new types of similarity reductions are performed. Some new exact solutions are obtained, which can be in the form of solitary waves, shock waves and periodic waves. Especially, our solutions indicate that the system may have time-dependent nonlinear shears. Some explicit similarity electrostatic wave solutions with time periodic nonlinear shears are displayed graphically.

Low frequency electrostatic waves in a cylindrically bounded dusty magnetoplasma with nonadiabatic dust charge fluctuation

A rigorous theoretical investigation is made for the low frequency electrostatic waves in a cylindrically bounded magnetized dusty plasmas with nonadiabatic dust charge variation, and the dispersion relation for the low frequency modes is derived. The combined effects of the cylindrical boundary, the external magnetized field, the nonadiabatic dust charge fluctuation, the nonthermally distributed ions and the ratio of electron to ion density on the low frequency waves are studied in great detail. It is shown that the mentioned effects have a strong influence on the dispersion properties of the low frequency modes.

Low-frequency electrostatic waves in the ionospheric E-region: a comparison of rocket observations and numerical simulations

Abstract. Low frequency electrostatic waves in the lower parts of the ionosphere are studied by a comparison of observations by instrumented rockets and of results from numerical simulations. Particular attention is given to the spectral properties of the waves. On the basis of a good agreement between the observations and the simulations, it can be argued that the most important nonlinear dynamics can be accounted for in a 2-D numerical model, referring to a plane perpendicular to a locally homogeneous magnetic field. It does not seem necessary to take into account turbulent fluctuations or motions in the neutral gas component. The numerical simulations explain the observed strongly intermittent nature of the fluctuations: secondary instabilities develop on the large scale gradients of the largest amplitude waves, and the small scale dynamics is strongly influenced by these secondary instabilities. We compare potential variations obtained at a single position in the numerical simulations with two point potential-difference signals, where the latter is the adequate representation for the data obtained by instrumented rockets. We can demonstrate a significant reduction in the amount of information concerning the plasma turbulence when the latter signal is used for analysis. In particular we show that the bicoherence estimate is strongly affected. The conclusions have implications for studies of low frequency ionospheric fluctuations in the E and F regions by instrumented rockets, and also for other methods relying on difference measurements, using two probes with large separation. The analysis also resolves a long standing controversy concerning the supersonic phase velocities of these cross-field instabilities being observed in laboratory experiments.

Relationship between dust acoustic waves in two and three dimensions

Low frequency electrostatic waves are investigated for a monolayer suspension of dust particles that are shielded by an ambient plasma of three-dimensional extension. The dispersion of the resulting dust acoustic surface waves is compared with dust acoustic waves in three dimensions and with lattice modes in two dimensions. It is found that the wave dispersion is determined by shielding of electric fields by electrons and ions on either side of the dust monolayer; this differs from previously studied cases of charged sheets in a vacuum. The phase velocity of these surface waves suggests the definition of a proper dust plasma frequency for monolayer systems.

Electron–ion attachment induced instability of dust acoustic waves in the presence of ionization in a charge varying collisional dusty plasma

Low frequency electrostatic dust acoustic wave (DAW) instability with a significant background pressure of neutrals has been investigated in a collisional dusty plasma incorporating the dust charge relaxation and electron–ion attachment (recombination) onto dust grains using a self consistent theory. A long wavelength mode is found to be unstable due to electron–ion attachment on to the dust grains. Applications to experimental observations of low frequency fluctuation and the relevance of these results to ‘void’ in a laboratory gas discharge dusty plasma are briefly discussed.

Parallel electron velocity shear instability in a magnetized plasma

It is shown that the parallel electron velocity shear can destabilize low-frequency (in comparison with the electron gyrofrequency) electrostatic waves in a magnetized plasma. A new dispersion relation is derived and solved for the parameters relevant for laboratory experiments of velocity shear instabilities in a magnetized plasma.

Plasma profiles, waves and anomalous transport in a purely toroidal plasma modified by a biased internal anode

Two-dimensional (2D) plasma profiles, gradient-driven low frequency electrostatic waves and anomalous particle transport are studied experimentally in a purely toroidal plasma configuration. The plasma is produced by a negatively biased, emissive cathode in conjunction with a variably biased anode plate localized on the same field line. Nearly circularly symmetric potential profiles, positive or negative, can be obtained by varying the anode plate bias. Confinement loss in the form of plasma ejection in the major radius direction is only observed when the anode is biased close to ground potential. For the cases of circularly symmetric plasma flow electrostatic flute modes with poloidal mode number m = 1 and m = 2 are identified as unstable on the low-field side of the density maximum, but indications are also given that they coexist with spatially quasi-uniform oscillations and, for low frequencies, with an ion acoustic mode with toroidal mode number n = 1 propagating parallel to the magnetic field. The anomalous particle flux density is found to be non-uniformly distributed on a toroidal surface, and the main flux is passed through two lobes directed almost vertically upwards and downwards, while almost no flux takes place along the major radius direction.