In this paper we investigate how the complex rotation and quivering motion of an elongated polarized dust grain in the presence of a monochromatic electromagnetic (EM) wave can produce dipolar emission with two distinct spectral components. We present a model for the emission of radiation by elongated polarized dust grains under the influence of both an external EM wave and a constant background magnetic field. The dust, exhibiting rotational motion at the external EM field frequency ω 0 as well as quivering motion at a frequency Ω0, proportional to the EM field amplitude, will radiate with frequencies that will depend on the external field wavelength and amplitude. The radiated spectra exhibits a frequency around ω0, and sidebands at ω0 ± ω0 and ω0± 2Ω0. Since the amplitude and the frequency of the background EM field are independent parameters, this model establishes a correlation between different spectral components of galactic dipolar emission, which may help to explain the correlation between a component of the Galactic microwave emission and the 100 μ m thermal emission from interstellar dust that has been recently measured.

Alfvénic states of a plasma, where velocity and magnetic field coincide, form a particular simple class of ideal equilibria and are also found in certain astrophysical phenomena. While transient processes of alignment in turbulent plasmas are well known and due to preferential spectral transfer, the possible long-term evolution of a magnetohydrodynamic plasma towards an alfvénic state has been rarely studied. It is shown that this tendency does not exist: neither specific ideal alfvénic equilibria nor the whole set of such states attract trajectories in any functional sense. Another possibility is that the perturbations of a static equilibrium could tend to become alfvénic, such as the classical Alfvén waves. We find that if these equilibria are current free, when a perturbation approaches an alfvénic state it immediately bounces away from it.

A study of particle and electron heat transport in tokamaks due to trapped-electron-mode (TEM) turbulence is presented. The study is based on the Weiland fluid model for ion-temperature-gradient (ITG) modes and TEMs, complemented and compared with a trapped electron fluid treatment which retains contributions from the weakly trapped electrons. The dependence of the fluid transport coefficients on magnetic shear and other plasma parameters is discussed and compared with results obtained from nonlinear gyrokinetic simulations. Inward (pinch) flows of particles and heat, previously reported for the coupled ITG–TEM system, are also found in the TEM dominated regime.

The efficiency of the Alfvén impulse excitation in the auroral zone of the terrestrial magnetosphere upon the onset of the anomalous field-aligned resistance has been estimated. The impulsive disturbance excited during the onset of anomalous field-aligned resistance and electric field may signify the transition of a global magnetospheric instability into the explosive phase with positive feedback. We consider the self-consistent problem on excitation of anomalous resistance at the front of field-aligned current and reverse influence upon it from the induced currents. The analytical solution of the self-consistent problem has shown that during the entrance of field-aligned current front into the anomalous resistivity layer (ARL) an Alfvénic impulse is generated. The interaction of the external current with ARL results in the delay of the current growth. The impulse duration and delay time depend on the ratio between the Alfvén damping scale and external current width. The solution obtained indicates the possibility of using the Alfvénic impulse as an indicator of distant occurrence of anomalous resistance.

A conducting source moving uniformly through a magnetized plasma generates, among a variety of perturbations, Alfvén waves. An interesting characteristic of Alfvén waves is that they can build up structures in the plasma called Alfvén wings. These wings have been detected and measured in many solar system bodies, and their existence has also been theoretically proven. However, their stability remains to be studied. The aim of this paper is to analyze the stability of an Alfvén wing developed in a uniform background field, in the presence of an incompressible perturbation that has the same symmetry as the Alfvén wing, in the magnetohydrodynamic approximation. The study of the stability of a magnetohydrodynamic system is often performed by linearizing the equations and using either the normal modes method or the energy method. In spite of being applicable for many problems, both methods become algebraically complicated if the structure under analysis is a highly non-uniform one. Palumbo has developed an analytical method for the study of the stability of static structures with a symmetry in magnetized plasmas, in the presence of incompressible perturbations with the same symmetry as the structure (Palumbo 1998 Thesis, Universidad de Firenze, Italia). In the present paper we extend this method for Alfvén wings that are stationary structures, and conclude that in the presence of this kind of perturbation they are stable.

We investigate numerically the magnetic flux and self-inductivity of a toroidal current I of arbitrary aspect ratio (R0/r0 = 1/η, where R0 and r0 are the major and the minor torus radii, respectively). The total flux Ψ is represented by the sum of the flux outside the torus envelope (Ψo) and the internal flux within the torus body (Ψi). Analogously, the total inductivity is expressed as L = Lo + Li. The outside self-inductivity is determined directly from the magnetic flux Ψo, utilizing Ψo = LoI. On the other hand, the internal inductivity is evaluated as the magnetic energy contained in the poloidal field. The calculations are performed for three different radial profiles of the current density, j(r).

It is found that Ψo(η) and Lo (η) depend only very weakly on the form of j(r). On the other hand, Ψi and Li do not depend on η, but depend on the form of j(r). In the range 0.02 ≲ η ≲ 0.5, the numerical values of Lo can be very well fitted by the function of the form Lofit1(η) = −A log(η) − B. Such a relation is analogous to that for a slender torus, although the coefficients are different. For η ≲ 0.01 the slender-torus approximation (Lo*) matches the numerical results better than our function Lofit1, whereas for thicker tori, Lofit1 becomes more appropriate. It is shown that, beyond η ≳ 0.1, the departure of the slender-torus analytical expression from the numerical values becomes greater than 10%, and the difference becomes larger than 100% at η 0.55. In the range η 0.5, the numerical values of Lo can be very well expressed by the function Lofit2(η)=c1 (1 − η)c2. Furthermore, since the internal flux and inductivity become larger than that outside the envelope, Ψi and Li become larger than Ψo and Lo. The total inductivity Ltotfit = Lofit + Li, calculated by appropriately employing our functions Lofit1 and Lofit2, never deviates by more than 1% from the numerically determined values of Ltot.

The properties of zonal flows in the toroidal ion temperature gradient mode turbulence are investigated taking into account the polarization drift effects. The stability criterion and the characteristic oscillation frequency of the zonal flow are determined in terms of the spectra of turbulent fluctuations. The nonlinear evolution of zonal flows may lead to the formation of stationary long-lived coherent structures supporting stationary shear layers. These results indicate the existence of regions with reduced levels of anomalous transport attributed to zonal flows generalizing previous findings regarding zonal flows in electron drift turbulence.

A system of nonlinear equations governing the transmission of uni-axial waves in a cold collisionless plasma subject to a transverse magnetic field is reduced to the recently proposed resonant nonlinear Schrödinger (RNLS) equation. This integrable variant of the standard nonlinear Schrödinger equation admits novel nonlinear superposition principles associated with Bäcklund–Darboux transformations. These are used here, in particular, to construct analytic descriptions of the interaction of solitonic magnetoacoustic waves propagating through the plasma.

The recent analysis of dust voids (Mamun, A. A. and Shukla, P. K. 2005 J. Plasma Phys.71, 143) is extended to include self-consistent electron trapping and dust charge variation. It is found that under certain conditions the effect of dust charge variation can be quite important. In particular, it may be noted that the dust charge variation leads to an additional enlargement of the nonlinear dust voids. The effects of ion/electron temperature and trapping parameter on the properties of these nonlinear dust voids are briefly discussed. As the dust particle number density is increased, the depth, as well as the width, of the dust void decreases and the additional enlargement (due to dust charge perturbations) becomes less pronounced. Furthermore, these dust voids exhibit smaller widths than those involving isothermal electrons.

A systematic first-principles approach to the many-particle formulation of the gyro-kinetic theory is suggested. The gyro-kinetic many-particle Hamiltonian is derived using the Lie transform technique. The generalized gyro-kinetic equation is obtained following the Born–Bogoliubov–Green–Kirkwood–Yvon approach. The microscopic expression for the self-consistent potential and the polarization density is obtained. It is shown that new terms appear in the gyro-kinetic polarization that can not be derived in the conventional approach. An expression for the collision term is obtained in the Landau approximation.

The efficiency of whistler wave radiation by a density modulated and thin electron beam of finite length injected parallel with respect to the constant ambient magnetic field into a cylindrical plasma column surrounded by a uniform isotropic medium and aligned along the magnetic field is studied. A rigorous analytical derivation of the wave fields excited by the beam in the plasma column is presented. The time-averaged power radiated by the beam at the modulation frequency is determined. In particular, numerical calculations performed for physical conditions relevant to laboratory magnetized discharge plasmas show that, in the presence of a plasma column, the power lost by the modulated beam can be efficiently enhanced owing to resonant Cherenkov excitation of guided whistler modes at the beam modulation frequency.

The dynamics of low-frequency, short-wavelength electrostatic (SWES) drift waves in a self-gravitating, non-uniform, collisional dusty magnetoplasma with equilibrium dust-velocity gradients is studied in the present work. By employing the dust continuity and momentum equations to describe the dust dynamics and Boltzmann distribution for the electrons and ions, we have derived a new set of nonlinear mode coupling equations. In the linear limit, it is found that SWES drift waves are subjected to dissipative instability in the presence of an equilibrium dust sheared flow and self-gravitation effect. On the other hand, in the nonlinear case, it is shown that possible stationary solutions of the nonlinear equations are dipolar vortices.

A theory of the drag force acting on an object immersed in a flowing plasma is presented. A control surface method is developed following the approach used in fluid mechanics rather than the linear dielectric response approach found in the literature. The situation examined is one in which the directed velocity of the ions dominates their thermal velocities; a cold ion model is employed.

The solution of the steady state of accretion disks surrounding non-rotating black holes is solved by numerical simulations, where we adopt a promising viscosity prescription (i.e. anomalous magnetic viscosity). We can describe the disk more exactly than other studies, because the viscosity we adopted is close to the truth accretion disk. In contrast to previous studies, the curve of the Mach number behaves differently owing to the decline of the local sound velocity with increasing radii.

The stability of these disks has been examined. We find that the O-mode (out-mode) is always unstable and its growth rate decreases monotonically with increasing wavelength, in the inner disk and in the outer disk. The I-mode (in-mode) is unstable in the outer disk, but stable in the inner disk when the wavelength is greater than a special value.

The nonlinear theory of large-amplitude magnetosonic (MS) waves in highβ space plasmas is revisited. It is shown that solitary waves can exist in the form of ‘bright’ or ‘dark’ solitons in which the magnetic field is increased or decreased relative to the background magnetic field. This depends on the shape of the equilibrium ion distribution function. The basic parameter that controls the nonlinear structure is the wave dispersion, which can be either positive or negative. A general dispersion relation for MS waves propagating perpendicularly to the external magnetic field in a plasma with an arbitrary velocity distribution function is derived.It takes into account general plasma equilibria, such as the Dory–Guest–Harris (DGH) or Kennel–Ashour-Abdalla (KA) loss-cone equilibria, as well as distributions with a power-law velocity dependence that can be modelled by κdistributions. It is shown that in a bi-Maxwellian plasma the dispersion is negative, i.e. the phase velocity decreases with an increase of the wavenumber. This means that the solitary solution in this case has the form of a ‘bright’ soliton with the magnetic field increased. On the contrary, in some non-Maxwellian plasmas, such as those with ring-type ion distributions or DGH plasmas, the solitary solution may have the form of a magnetic hole. The results of similar investigations based on nonlinear Hall–MHD equations are reviewed. The relevance of our theoretical results to existing satellite wave observations is outlined.

The transitions and the self-gravitational effects on the surface dust-ion-acoustic mode are investigated in semi-bounded magnetized dusty plasmas. We find that there is a dust-ion-acoustic resonance mode in small wave number regions. Furthermore, we find that the self-gravitational effects enhance the resonance frequency. However, the surface wave starts to propagate as the wave number increases. The transition position between the resonance oscillation and the wave propagation is shifted to the smaller wave number domain as self-gravitational effects increase. In addition, the resonance frequency is found to decrease with decreasing strength of the magnetic field in small wave number domains.

The collision integral that describes the evolution of a distribution of particles in a plasma due to Coulomb interactions between themselves or with other particles is generalized to include relativistic effects and the current–current interaction (in addition to the charge–charge interaction). This is achieved through a covariant version of a conventional derivation based on correlation functions for fluctuations in the plasma. The covariant theory is used to distinguish between longitudinal (charge–charge) and transverse (current–current) interactions. For highly relativistic particles, the current–current contribution is half the charge–charge contribution when Debye screening is unimportant, and is unaffected by Debye screening. It is shown that the classical theory is reproduced by a quantum electrodynamics calculation for electron–electron (Møller) scattering in the limit of small momentum transfer.

In this paper, we use numerical modeling to study some characteristics of the XeCl laser under homogeneous pre-ionization conditions. The study is executed using a model combining external circuit and plasma kinetics. The model validity is checked by comparing the model results to the experimental data from the literature. A qualitative agreement was found.

The study of dusty plasmas is of significant practical use and scientific interest. A characteristic feature of dust grains in a plasma is that they are typically smaller than the electron Debye distance, a property which we exploit using the technique of matched asymptotic expansions. We first consider the case of a spherical dust particle in a stationary plasma, employing the Allen–Boyd–Reynolds theory, which assumes cold, collisionless ions. We derive analytical expressions for the electric potential, the ion number density and ion velocity. This requires only one computation that is not specific to a single set of dust–plasma parameters, and sheds new light on the shielding distance of a dust grain. The extension of this calculation to the case of uniform ion streaming past the dust grain, a scenario of interest in many dusty plasmas, is less straightforward. For streaming below a certain threshold we again establish asymptotic solutions but above the streaming threshold there appears to be a fundamental change in the behaviour of the system.