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Controlling and mitigating plasma disruptions are a matter of serious concern for tokamak operation since they can cause serious damage to the machine. Dedicated experiments on disruption mitigation have been carried out in ADITYA (R = 75 cm, a = 25 cm), an Ohmically heated circular limiter tokamak. A rapid growth of magneto hydrodynamic (MHD) modes is found to be the major cause of disruptions in ADITYA tokamak. Stimulated disruptions induced by hydrogen gas puffing are successfully mitigated through stabilization of these MHD modes by applying a biased-electrode placed inside the last-closed flux surface prior to the gas injection. However, as biased electrodes cannot be placed inside the plasma in bigger tokamaks, the application of ion-cyclotron waves (ICWs) prior to disruption has been successfully attempted to mitigate disruptions through stabilization of MHD modes in ADITYA tokamak. The amplitude of MHD modes (m/n = 3/1, 2/1) is significantly reduced upon the application of ICW prior to disruption, and the stimulated disruptions are successfully mitigated by preventing the growth and overlapping of these MHD modes. These experimental results demonstrate that MHD driven disruptions may be mitigated due to stabilization of m = 2 modes by ponderomotive force of the IC waves.

The nonlinear interaction of a circularly polarized Gaussian intense laser pulse in a collisionless cold plasma with immobile ions is analyzed. The laser beam is assumed to have a nonuniform intensity distribution (along its wave front) in a plane transverse to the direction of propagation. To properly include the nonuniformity of the laser field, the wave equation is integrated over the transversal distribution. In this way, the mean transversal effects are taken into account. In this frame of work the relativistic modulational instability (RMI) of a long pulse is analyzed. A general dispersion relation is derived and solved. Plots of the temporal growth rate as a function of the laser beam power and the modulation wave number are presented and compared with the case when a uniform intensity distribution along the laser wave front is assumed. It is found that the nonuniformity of the laser beam has a significant effect on the characteristics of RMI. It is shown as a conclusion that the effect of transverse distribution in the growth rate reduction, in comparison with the case when it was neglected, becomes more significant for shorter wavelength of the RMI and stronger pump waves.

Coherent nonlinear stationary state is studied in the frequency and spatial domain of electromagnetic lower-hybrid waves in a beam-plasma configuration that is subjected to the oblique linear Buneman instability. In the presence of magnetic shear, a solution is found in the form of a nonlinear chain of magnetic islands. Such equilibrium may represent the saturated state of fast collisionless magnetic reconnection that is reached after the reconnection has ended. It is demonstrated that the topological constraints that hamper the reconnection of magnetic field lines in the fluid representation are efficiently removed by the nonlinear currents and space charges of trapped electrons. Two distinct trapping mechanisms are distinguished. Besides the electrostatic trapping of particles in the self-consistent minima of potential energy, a different type of magnetic trapping is identified that is responsible for the creation of thin current sheets at the separatrices between open and closed magnetic field lines. C...

An analytical model based on Lagrangian variables is presented for the description of ion-acoustic waves propagating in an unmagnetized, collisionless, three-component plasma composed of inertial positive ions and two thermalized electron populations, characterized by different temperatures. The wave’s amplitude is shown to be modulationally unstable. Different types of localized envelope electrostatic excitations are shown to exist, and their forms are analytically and numerically investigated in terms of the plasma dispersion and nonlinearity laws. These results are in qualitative agreement with satellite observations in the magnetosphere.

Nonlinear interactions between electromagnetic electron cyclotron (EMEC) waves and ion-acoustic perturbations involving nonisothermal electrons and cold inertial ions are considered. Following standard methods, a reduced wave equation for the slowly varying EMEC wave envelope is derived, including nonlinear effects associated with relativistic electron mass variation and electron density changes caused by the EMEC ponderomotive force and trapped electrons in the ion-acoustic perturbations which modulate the EMEC waves. The governing equations are employed to investigate the influence of trapped electrons on the modulational instability and envelope EMEC solitons. It is found that the static magnetic field intensifies the reduction of the growth rate, and makes the conditions for constructing envelope soliton solutions harder.

The derivative correction to the Heisenberg–Euler Lagrangian has been introduced. A general dispersion relation for a photon traveling on a slowly varying background electromagnetic field has been presented. A set of equations describing the nonlinear propagation of an electromagnetic pulse on a radiation fluid background is then derived. Novel modulational and filamentational instabilities are found, and using numerical methods, it has been shown that electromagnetic pulses may collapse and split into pulse trains. Also presented are analytical results concerning the collapse, split, and Mach cone formation. The implications of the results are discussed.

The possibility for the formation of Mach cones in a dusty magnetoplasma containing elongated charged dust grains has been examined theoretically. It is predicted that the Mach cones can be formed by dipole oscillons (wave modes associated with the oscillations of dust dipoles around their mean positions) in a laboratory plasma containing elongated (rodlike) negatively charged dust grains. An experiment in radio-frequency dusty plasma discharges should be conducted for verifying the theoretical prediction that has been made here.

The problem of the plasma-wall transition (PWT) layer in an unmagnetized plasma is considered, without the usual splitting into a sheath and presheath region. The electrons are assumed to be Boltzmann distributed, while the ion dynamics is described by a kinetic theory which includes ionization, recombination, and charge exchange. A condition is derived, which must be fulfilled by the ion velocity throughout the whole PWT in order to exclude oscillatory behavior of the electrostatic potential. The resulting system of equations is solved numerically for various physical situations. The Harrison–Thomson solution for the Tonks–Langmuir model is extended to the case where the quasineutrality is violated, and it is shown that the parabolic shape of the potential profile is retrieved also in this case. For a complete PWT layer, good agreement with recent experimental observations is demonstrated, whereas marked disagreement is found with results based on theories where no recombination is included and/or the ratio of Debye length to characteristic presheath length is assumed to be infinitesimally small. A comparison between recent experimental results with a numerical solution of the model presented here reveals that the model accurately describes the transition from the bulk plasma to the electron-free plasma sheath.

Nonlinear interactions between ultraintense laser pulses and plasmas reveals a great variety of important collective phenomena. Advances in laser technology have made possible compact terawatt lasers capable of generating subfemtosecond pulses at ultrahigh intensities. These ultrahigh intensities result in highly relativistic nonlinear electron dynamics. This paper addresses stationary stage of the interaction of an ultraintense short laser pulse with a plasma including finite spot size effects. The study is based on the approach that accounts for the transversal effects in an average manner. Following the standard method, a reduced wave equation for the slowly varying laser envelope is derived, including nonlinear effects associated with relativistic electron mass variation and relativistic ponderomotive force. Localized and periodic solutions of the envelope equation are presented and compared with the case when the transversal distribution is infinite. It is found that the finite transverse size of laser spot has significant effects on the propagation characteristics of the stationary profiles.

The weakly nonlinear regime of transverse paramagnetic dust grain oscillations in dusty (complex) plasma crystals is discussed. The nonlinearity, which is related to the sheath electric/magnetic field(s) and to the inter--grain (electrostatic/magnetic dipole) interactions, is shown to lead to the generation of phase harmonics and, in the case of propagating transverse dust-lattice modes, to the modulational instability of the carrier wave due to self--interaction. The stability profile depends explicitly on the form of the electric and magnetic fields in the plasma sheath. The long term evolution of the modulated wave packet, which is described by a nonlinear Schr\"odinger--type equation (NLSE), may lead to propagating localized envelope structures whose exact forms are presented and discussed. Explicit suggestions for experimental investigations are put forward., Comment: 9 pages, 4 figures, submitted to Physics of Plasmas

It is shown that a dust void in a dusty plasma can be formed due to the presence of positive plasma potential, which is built up owing to a nonisothermal dust particle distribution arising from negatively charged dust particle trapping. It is found that the dust void shrinks with the increase of the dust charge density, while it enlarges with the increase of the dust temperature. The implications of our results to the possibility for the formation of dust voids in space dusty plasmas, particularly in Saturn’s dusty rings, is discussed.

The occurrence of the modulational instability (MI) in transverse dust lattice waves propagating in a one-dimensional dusty plasma crystal is investigated. The amplitude modulation mechanism, which is related to the intrinsic nonlinearity of the sheath electric field, is shown to destabilize the carrier wave under certain conditions, possibly leading to the formation of localized envelope excitations. Explicit expressions for the instability growth rate and threshold are presented and discussed., 5 pages, no figures; submitted to Physics of Plasmas

The dispersion properties of low-frequency (in comparison with the ion gyrofrequency) dust-electromagnetic waves in a four-component magnetized dusty plasma have been investigated. It has been shown that the simultaneous presence of positive and negative inertial dust grains introduces new resonance and cut-off for dust-electromagnetic waves, and a sharp forbidden- frequency-band in between the two branches of the propagating dust-electromagnetic waves. The two wave branches have been found to have frequencies of the order of negative and positive dust gyrofrequencies, respectively. The effects of space and laboratory dusty plasma parameters on these newly found resonance and cut-off and on the dispersion properties of the dust-electromagnetic wave branches have also been examined.

Strong kinetic heating of grains is frequently associated with a melting transition in plasma crystals. At high pressures, above 100 mTorr, the melting transition is preceded by a vibrational phase whereas at low pressures, below 50 mTorr, observed large amplitude self-excited oscillations can lead to lattice disruption. At such low background gas pressures, only single layer crystals are formed. This work focuses on the low pressure regime and provides a theory of the self-excited oscillations which explains both the pressure and the power dependence of these oscillations as well as their threshold behavior. The implications for the melting transition are pointed out.

This paper presents an investigation of the growth of a Gaussian perturbation on a uniform plane wave front of an Alfven wave (AW). The effect of the nonlinear coupling between the main AW and the perturbation has been studied. The dynamical equation for the field of the perturbation has been established and its semianalytical solution has been obtained in low (β≪me/mi) and high (β≫me/mi) β cases (β≪1). The critical field of the perturbation has been evaluated for the given size of the perturbation for its filamentation process (hot spot formation). Nonlinear evolution of the perturbation into filamentary structures and its dependence on various parameters of the solar wind and corona has been investigated in detail.

The interaction between relativistic ion beams, electrostatic waves and particles in plasmas is studied numerically. This beam-particle interaction is important for the acceleration of electrons above the threshold, where they can perform Fermi acceleration across shocks perpendicular to the magnetic field direction. The electrons form Bernstein–Greene–Kruskal (BGK) modes, which are unstable due to a sideband instability. This process heats the electrons to relativistic temperatures and the electrons finally attain a flat-top momentum distribution with exponentially decreasing tails of the momentum distribution function. A scaling law, depending on the ion beam speed, is found for the electron distribution function. Furthermore, in the fully nonlinear phase, ion phase space vortices, or proton BGK modes are formed in the beam, which continue to interact with the electrons after the electron BGK modes have collapsed.

Using dynamical techniques of the plasma physics, the neutrino (antineutrino) effective charge in a magnetized dense electron–positron plasma is determined here. It shown that its value, which is determined by the plasma collective processes, depends mainly on the propagation direction of plasma waves and neutrinos against the external magnetic field direction. The direction dependence of the effective charge occurs due to the fact that the magnetic field breaks the plasma isotropy. The present theory gives a unified picture of the problem which is valid for an external magnetic field below the Landau–Schwinger critical value. Comparison with some of the results from the quantum field theory has been made.

A complete theory for Langmuir envelope solitons in an unmagnetized dusty plasma is presented, taking into account interactions between finite amplitude Langmuir waves and fully nonlinear dust ion-acoustic (DIA), dust acoustic (DA), and ion hole (IH) perturbations. For this purpose, a nonlinear Schrodinger equation is employed for the Langmuir wave envelope and expressions for plasma slow responses are derived, including a modified (by the Langmuir waveponderomotive force)Boltzmann electron distribution and appropriate ion and dust density distributions for fully nonlinear dispersive DIA, DA, and IH perturbations, which include departure from the quasi-neutrality condition. In the stationary frame, the governing equations can be cast in the form of a Hamiltonian which is used to check the accuracy of the numerical scheme predicting stationary localized solutions of our governing nonlinear equations. Numerical results reveal different classes of Langmuir envelope solitons (cavitons) whose features differ from those in an electron-ion plasma without dust. Ion and dust thermal effects for the DIA and DA waves, respectively, have been included. It is suggested that new beam-plasma experiments in laboratory dust plasmas should be conducted to verify our theoretical predictions of cavitons.

The magnetic-curvature-driven interchange mode instability of a weakly inhomogeneous dusty plasma is rigorously investigated. It is shown that the electric drift convection of the equilibrium dust charge density is a stabilizing factor for long wavelength interchange modes. In a fully nonlinear regime, the finite amplitude interchange modes may self-organize in the form of a dipolar vortex. The present results should be useful in the understanding of the properties of the interchange mode turbulence in nonuniform magnetized plasmas containing charged dust particles.

A self-consistent and complete theory for linear, weakly nonlinear, and highly nonlinear dust-hydromagnetic waves in a magnetized dust-ion plasma has been presented. Oblique propagation as well as two typical special cases, propagation along and across the ambient magnetic field direction, are considered. The linear dispersion properties are analyzed by using the normal mode analysis. The weakly nonlinear properties are studied by employing the reductive perturbation method, which is valid for small but finite amplitude waves. The highly nonlinear properties are investigated by means of a pseudopotential approach, which is valid for arbitrary amplitude waves. The implications of our results to some space and astrophysical dusty plasmas are briefly mentioned.

Theoretical and numerical studies are carried out of the nonlinear amplitude modulation of dust-ion acoustic waves propagating in an unmagnetized weakly coupled plasma comprised of electrons, positive ions, and charged dust grains, considering perturbations oblique to the carrier wave propagation direction. The stability analysis, based on a nonlinear Schrodinger-type equation, exhibits a wide instability region, which depends on both the angle θ between the modulation and propagation directions and the dust number density nd. Explicit expressions for the instability increment and threshold are obtained. The possibility and conditions for the existence of different types of localized excitations are also discussed.

Nonlinear interactions between large amplitude upper-hybrid waves and low-frequency electromagnetic waves in a magnetized plasma have been considered. Specifically, the decay of upper-hybrid waves into lower-hybrid and magnetosonic waves, as well as the modulational instabilities leading to the formation of density cavities which trap upper-hybrid wave envelopes, are investigated both theoretically and numerically. It is found that the three-wave process between two upper-hybrid waves and the lower-hybrid wave, which is the fastest growing instability of the system, is important for the generation of waves of small wave numbers, via the self-interaction of the generated decay products from the three-wave interaction. A comparison between the theory of the parametric decay, simulations of a generalized Zakharov system of equations modeling the interaction between upper-hybrid, lower-hybrid and magnetosonic (fast Alfvenic) waves is presented. Comparisons are made with a simulation of the fully electromagnetic Vlasov–Maxwell system for ions and electrons where a sudden onset of cavities and long wavelength magnetosonic wave emission could be seen, similar as in the simulation of the Zakharov-type system.

The effect of an external magnetic field on the Debye shielding and dynamical wake potentials has been examined analytically in a uniform dusty plasma containing equilibrium ion and dust flows. The effects of the ion polarization drift and dust particle dynamics on the strength and the effective length of the new static Debye shielding potential and the dynamical oscillatory potential are studied. It is found that for the supersonic ion flow, the modified Debye–Huckel screening length, and the effective length, L∥, of the oscillatory wake potential due to the modified dust acoustic modes [cf. Eqs. (7) and (17)] become larger by a factor of ωpi/ωci than those due to the usual dust-acoustic wave, where ωpi and ωci are the ion plasma and ion gyrofrequencies, respectively.

Recent laboratory observations conclusively reveal that coherent nonlinear waves and structures (viz., solitons, shocks, Mach cones, voids, vortices, etc.) can be produced in a dusty plasma. Our objective here is to describe the underlying physics, mathematical details, and salient features of dust ion-acoustic as well as dust acoustic solitary and shock waves, dust voids, and dust vortex flows. It is shown that the presence of charged dust grains introduces new features to the nonlinear electrostatic waves and structures. Consideration of the dust charge fluctuation dynamics causes a novel dissipation, which is responsible for the formation of dust ion-acoustic shock waves. Furthermore, the formation of a dust void is associated with double layers and ion holes arising from trapped ion effects. Finally, a nonlinear model for dust vortex flows is presented. It is shown that the dynamics of dust vortex flows in a plasma is governed by a modified Navier–Stokes equation (MNSE), and that possible stationary solutions of the MNSE can be represented as monopolar as well as a row of identical and a row of counter-rotating vortices. The implications of our theoretical results/models to experimental observations of solitary and shock waves as well as of voids and vortices are discussed.

This paper presents the model equations, governing the coupling of the right and left circularly polarized Alfven waves, using Hall magnetohydrodynamics (MHD) equations. The solution of these model equations has been obtained by using analytical and numerical methods to study the effect of their mutual nonlinear interaction on filament formation, the critical size of the filaments and the threshold in the compressible Hall MHD case. The coupling between the two modes may be so effective that the formation of periodic filaments, separated by a distance of the order of 900 kms and a transverse size of the order of 2.3×105 kms, can be predicted for typical solar wind parameters. The effect of coupling on Faraday rotation and ellipticity has also been studied. Its effect on solar wind turbulence has been pointed out.

Decay instabilities and Kolmogorov-type spectra of weakly turbulent shear-Alfven waves in dusty plasmas are analyzed in the limit when the wave dispersion is produced solely by the dust grain density inhomogeneity. It is shown that the reduced equations for weakly nonlinear and dispersive waves possess two conservation laws for the wave energy and generalized enstrophy. It turns out that the weakly turbulent plasma Kolmogorov spectra associated with these conservation laws are nonlocal. It is found that the presence of a dust grain inhomogeneity leads to the formation of an Iroshnikov–Kraichnan type energy spectrum related to the energy conservation law. The possibility of the existence of such spectra in space plasmas is discussed. The specific features of the obtained energy spectra can be used for the identification of dust grains in the Earth’s ionosphere, the solar wind and the interstellar medium using the data collected by magnetometers onboard satellites.

It is shown that the resonant streaming energy associated with cross-field motions (due to the cross product of dc electric and magnetic fields) of the plasma particles can be coupled to low-frequency electrostatic waves. Conditions under which unstable waves appear are obtained for both collisionless and collisional dusty magnetoplasmas. The relevance of the present investigation to understanding the origin of nonthermal fluctuations in laboratory and space plasmas is pointed out.

A classical fluid description is used to investigate the nonlinear interaction between neutrino bursts and a relativistic collisionless cold unmagnetized plasma. It is shown that during the interaction large amplitude electron plasma waves are excited in such a way that charged particles trapped in this high gradient potential can be accelerated to extremely high energies.

Stability of a thin current sheet in an inhomogeneous dusty plasma is investigated. A new mechanism for the collisionless reconnection of the magnetic field is found. It is associated with the linear instability of a surface shear-Alfven mode which exists at the boundary between two plasma regions with different orientations of the sheared magnetic field. This new mode is possible only in dusty plasmas in which the electron and ion densities are inhomogeneous and different from each other. The dispersion properties of the surface mode are found to be strongly dependent on the spatial profile of the current sheet. The unstable linear mode is found in the case of a current sheet with steep edges. It is identified as the bending- (or kink-) mode, whose electrostatic and vector potentials, φ and Az, are symmetric and antisymmetric functions, respectively. In such a plasma configuration, the surface tearing mode (φ-antisymmetric, Az-symmetric) cannot propagate as an eigenmode. It arises only as a forced mode t...

The evolution of initially sufficiently asymmetric super-strong laser pulse propagating in underdense cold plasma is studied. The effects of the relativistic electron mass increase and the repelling of electrons by the ponderomotive force from the central regions of laser beam propagation are taken into account. The beams with spot sizes much smaller than the pulse length are investigated. The beam, as well as plasma, characteristic parameters are obtained in the overcritical propagation regime, ignoring ion motion when the pulse self-focusing, self-guiding and filamentation take place. The role of the striction effect in the electron cavitation and ion channel formation phenomena is investigated. It is shown that, for specific parameters, the strongly asymmetric beam transforms to a symmetric one and later propagates in the plasma for a long distance.

The nonlinear interaction between intense neutrino beams and sound waves in dense plasmas is considered. Accordingly, a Schrodinger-type equation is derived for the amplitude wave function of neutrinos interacting with a background plasma via the weak Fermi force. The neutrino driving (ponderomotive) force pushes the plasma electrons locally, thereby creating space charge electric fields through which the inertial ions are reinforced. It is shown that the nonlinearly coupled neutrinos and the ion sound perturbations are responsible for the formation of stationary envelope solitons and nonstationary shocks. The relevance of these nonlinear structures to supernova explosions is pointed out.

A large number of laboratory observations reveal the formation of ordered linear chains and sheets composed of charged dust grains levitated in the sheath region of radio-frequency or dc plasma discharges at very low pressures. At higher pressures, three-dimensional structures are typically formed. Recently, a number of low gas pressure experiments have explored the generation of large amplitude vertical oscillations by lowering either the background pressure or the plasma power below a threshold value, or by imposing an external force that arises from a low-frequency sinusoidal voltage in the sheath region. A theoretical model is presented that successfully describes the phenomenology in various experiments, including the observed self-excited oscillations, nonlinear resonance and parametric oscillations. A new forcing mechanism, namely the modulational forcing, for exciting nonlinear resonances is proposed.

A set of equations describing the nonlinear dynamics of drift-Alfven waves in a dusty plasma accounting for the nonzero ion temperature gradients is derived. It is shown that these new equations yield a solution in the form of two-scale dipolar vortex structures propagating with velocities close to the ion-drift velocity in a narrow cone centered around the direction perpendicular to both the external magnetic field and the plasma gradient directions. The typical scales, characteristic vortex velocities as well as the relevant conditions for their existence are discussed. It is shown that nonzero ion temperature gradients substantially enlarge the range of possible propagation directions and characteristic scales of the vortex structures.

A theoretical investigation is carried out for understanding the properties of obliquely propagating electron-acoustic solitary waves (EASWs) in a magnetized plasma whose constituents are a cold magnetized electron fluid, hot electrons obeying a vortex-like distribution, and stationary ions. It is found that the present plasma model supports EASWs having a positive potential, which corresponds to a dip (hump) in the cold (hot) electron number density. The effects of the external magnetic field and the obliqueness are found to significantly change the basic properties (viz. the amplitude and the width) of the EASWs. The present investigation can be of relevance to the electrostatic solitary structures observed in various space plasma environments (viz. the cusp of the terrestrial magnetosphere, the geomagnetic tail, the auroral regions, etc.).

The linear and nonlinear properties of electromagnetic waves, which are excited by a nonuniform electron current almost parallel to the magnetic field lines, are studied in a pair (electron–positron) plasma. The strongly nonlinear stage of weakly interacting modes is controlled by a vector-product type nonlinearity. The latter is responsible for the formation of a dipolar vortex whose salient features are described analytically.

The locality of weakly turbulent Kolmogorov spectra for the ion-drift waves in dusty plasmas and the flute waves in electron-ion plasmas is analyzed. Using a standard kinetic approach for the description of the wave turbulence it is shown that the wave spectrum associated with the enstrophy flux is nonlocal whereas that related to the energy flux is local. The nonlocality of the wave enstrophy spectrum is associated with the long wavelength part of the turbulence. It is found that the wave energy flux is directed to smaller spatial scales.

The interaction of nonlinear ion-drift waves in a low β, that is me/mi≪β≪1, dusty plasma is investigated. The matrix elements of the three-wave interactions in an inhomogeneous plasma with uniform ion temperature are derived. The decay instability growth rates and weakly turbulent plasma wave spectra of the ion-drift waves are evaluated and analyzed.

Accounting for a nonequilibrium charging process in a positive dust–electron plasma, a theory is developed for a quasi-neutral layer separating the near-wall space–charge sheath from the bulk plasma where the charging of the dust grains is quasi-equilibrium (i.e., the current of the electrons emitted by a dust grain is approximately equal to the current of the electrons collected by the grain). The problem is solvable when the velocity of the dust particles entering the layer from the quasi-equilibrium plasma satisfies an inequality which is mathematically, although not physically, similar to the Bohm criterion. The obtained results explain the reason for the absence of a continuous transition from the Bohm criterion in a dusty plasma with a variable dust particle charge to the conventional Bohm criterion for an electron–ion plasma with constant ion charge.

The nonlinear dynamical equation for the propagation of kinetic Alfven waves has been derived in two dimensions using the two-fluid model of the plasma and by taking the adiabatic response for the background density in the presence of nonlinear electron heating and the ponderomotive force. Dynamically evolving filamentary structures are predicted. The effect of these filaments on solar wind turbulence and coronal heating has also been pointed out.

The nonlinear coupling between finite amplitude inertial Alfven (IA) and dust acoustic (DA) waves in a complex plasma is considered. By employing a multi-fluid dusty plasma model, which includes the effects of the ponderomotive force on the DA waves, a system of coupled equations is derived and used to study modulational instabilities of a constant amplitude IA wave. The results may have relevance to nonlinear phenomena involving IA and DA waves in low-temperature laboratory and space plasmas.

Linear and nonlinear low-frequency modes in a magnetized electron plasma are studied, taking into account a proper description of the equilibrium plasma state that is inhomogeneous. Assuming a homogeneous magnetic field and sheared plasma flows, flute-like perturbations are studied in the presence of density and potential gradients. Linear analysis reveals the presence of a streaming instability and depicts conditions for global linear spiral mode. In the nonlinear domain, a tripolar vortex, which is driven and carried by the flow, is found. Also investigated are the consequences of a magnetic shear as well as nonuniformities along the magnetic field lines, which are shown to be responsible for the possible annulment of the magnetic shear effects. Streaming along the lines of the sheared magnetic field is also studied. A variety of nonlinear structures (viz. global multipolar vortices, local vortex chains, and tripolar vortices) is shown to be the consequence of the simultaneous action of the parallel and perpendicular flows.

The dispersion properties of obliquely propagating ultra-low-frequency electromagnetic shear Alfven-like waves in a weakly ionized, self-gravitating, nonuniform dusty magnetoplasma are examined. It is found that the electromagnetic shear Alfven-like waves having the wavelength of the order of 10 AU and the wave period of the order of 30 000 years are unstable due to the effect of the self-gravitational force acting on the dust grains. The present investigation may be of relevance to the regions (namely, “warm photodisassociation regions”) at the boundary between molecular clouds and H II regions surrounding hot early type stars.

Two omnipresent ingredients of the Universe are plasmas and charged dust. The interplay between these two has opened up a new and fascinating research area, that of dusty plasmas, which are ubiquitous in different parts of our solar system, namely planetary rings, circumsolar dust rings, the interplanetary medium, cometary comae and tails, as well as in interstellar molecular clouds, etc. Dusty plasmas also occur in noctilucent clouds in the arctic troposphere and mesosphere, cloud-to-ground lightening in thunderstorms containing smoke-contaminated air over the United States, in the flame of a humble candle, as well as in microelectronic processing devices, in low-temperature laboratory discharges, and in tokamaks. Dusty plasma physics has appeared as one of the most rapidly growing fields of science, besides the field of the Bose–Einstein condensate, as demonstrated by the number of published papers in scientific journals and conference proceedings. In fact, it is a truly interdisciplinary science becaus...

It is shown that the nonlinear equation governing the dynamics of coupled dust-acoustic and dust-cyclotron waves in a magnetized dust-ion plasma can be written in the form of an energy integral. The latter is analyzed analytically as well as numerically to investigate the properties of arbitrary amplitude solitary waves. It is found both analytically as well as numerically that there exist solitary waves only with a negative potential. The implications of these results to some space and astrophysical dusty plasma systems, especially to planetary ring systems and cometary tails, are briefly discussed.