In the Earth's magnetosphere, the boundary layer regions are the sources for inhomogeneous plasmas and are natural laboratories to study wave phenomena. In these regions, particles distributions also differ from Maxwellian and are found to be non-thermal. Therefore, amplitude of the waves propagating through these regions can vary differently compared to the homogeneous plasmas. In this study, propagation of ion–acoustic waves (IAWs) in an inhomogeneous, warm electron-ion plasma is examined. The electrons are considered to be having non-thermal Cairn's type distribution and ions follow the fluid dynamical equations. Further, inhomogeneity is assumed in equilibrium density of the electrons and ions. The evolution of the nonlinear IAWs is governed by the Korteweg–de Vries (KdV) equation with variable coefficients. Analytical solution of the KdV equation shows that for a cold ion plasma and non-thermal electrons, the amplitude and the width of the nonlinear IAWs decreases and increases, respectively with the inclusion of the non-thermal distribution of electrons. It is interesting to note that nonlinear IAWs in this model can not propagate for whole range of non-thermal parameter, α. The novel result of this study is that for nonlinear IAWs to propagate in the inhomogeneous two component plasma with ions and non-thermal electrons, the non-thermal parameter, α ⩽ 0.155. Results from our study may have impact on the propagation of the IAWs in the boundary layer regions of the Earth's magnetosphere where density inhomogeneities are appreciable.

The properties of dust ion acoustic rogue waves (DIARWs) in an unmagnetized collisionless plasma system composed of charged dust grains, superthermal electrons and warm ions as a fluid are studied. The multiple scale perturbation method is used to derive a nonlinear Schrödinger equation (NLSE) for DIARWs. From the coefficients of nonlinearity and dispersion, we have determined the critical wave number threshold kcr at which modulational instability sets in. This critical wave number depends on the various plasma parameters, viz. superthermality of electrons, ion temperature and dust concentration. Within the modulational instability region, a random perturbation of amplitude grows and thus, creates DIARWs. It is found that DIARWs are significantly affected by electron superthermality (via κ), ion temperature (via σ) and dust concentration (via f). In view of the crucial importance of DIARWs in space environments, our results may be useful in understanding the basic features of DIARWs that may occur in space plasmas.

Saturation-power enhancement of a free-electron laser (FEL) amplifier by using tapered wiggler amplitude is based on the postponement of the saturation length of the uniform wiggler. In this paper, we qualitatively and quantitatively demonstrate that the saturation-power enhancement can be approached by means of the parameters adjustment, which is comparable to that by using a tapered wiggler. Compared to the method by tapering the wiggler amplitude, the method of parameters adjustment substantially shortens the saturation length, which is favorable to cutting down the manufacture and operation costs of the device.

Plasma expansion and soliton formation in laser created plasma are addressed. Nonlinear acoustic waves in plasma where the combined effect of trapped and non-thermal electrons are dealt with, in plasma expansion are studied. Using the perturbation method, a modified Korteweg–de Vries equation (mKdV) that describes how the ion acoustic waves (IAW) are derived. The plasma is modeled by a Cairns distribution function for non-thermal electrons combined with Gurevich distribution function for the trapped electrons. It is found that parameters taken into account have significant effects on the properties of nonlinear waves as well as on plasma expansion into vacuum. We point out, that this work has been motivated by space and laboratory plasma observations of plasmas containing energetic particles, combined with trapped particles. Furthermore, this study is of interest in the context of the investigation of mono-energetic ion beams from intense laser interactions with plasmas.

It is shown that there exists a strong interaction between the magnetic and kinetic aspects of a multi-ion plasma. The interaction appears as a system of simultaneous equations which show the alignment of vortices to flows and satisfy the Beltrami condition. Solving these equations lead to a non-force-free magnetic field which can be cast as a superposition of three multiscale force-free magnetic field configurations. It is the consequence of different Beltrami parameters of positive and negative ion fluids. It is also shown that self-organized paramagnetic and diamagnetic field structures could be created by varying the vorticities and flows of ion fluids.

In this paper, we focus on the numerical investigation of the vircator with a controlling emission from a field-emission cathode. The external harmonic signal is added to the accelerating electric field in the beam formation region and effects on the beam emission process leading to the electron emission modulation. As a consequence, the beam is injected into the drift chamber of the vircator being density-modulated. The strong influence of the modulation parameters (modulation depth and frequency) on the characteristics of virtual cathode oscillations has been discovered. We have shown that the tuning of the modulation frequency to the harmonics of the basic frequency of virtual cathode oscillations leads to the considerable power increase of its higher harmonics in the output spectrum.

The experiments revealed that ball lightning is a self-confining quasi-neutral in a whole plasma system that rotates around its axis. Ball lightning has a structure of a spherical electric domain, consisting of a kernel with excess negative charge and an external spherical layer with excess positive charge. The excess of charges of one sort and the lack of charges of the other sort in the kernel or in the external spherical layer significantly reduces the possibility of electron capture by means of an electric field, created by the nearest ions and leads to a drastic slowdown of recombination process. Direct proof has been obtained that inside of ball lightning – in an external spherical layer that rotates around the axis – there is a circular current of sub-relativistic particles. This current creates and maintains its own poloidal magnetic field of ball lightning, i.e. it carries out the function of magnetic dynamo. The kernel of ball lightning is situated in a region with minimum values of induction of the magnetic field. The inequality of positive and negative charges in elements of ball lightning also significantly reduces losses of the charged plasma on bremsstrahlung. Ball lightning generation occurs in a plasmic vortex. The ball lightning energy in the region of its generation significantly differs from the ball lightning energy, which is drifting in space. The axial component of kinetic energy of particles slightly exceeds 100 keV and the rotational component of the ions energy is a bit greater than 1 MeV. Ball lightning is ‘embedded’ in atmosphere autonomous accelerator of charged particles of a cyclotron type due to self-generation of strong crossed electric and magnetic fields. A discussion of the conditions of stability and long-term existence of ball lightning is given.

A new equation for the kinetics of nonlinear conversion of Langmuir waves to electromagnetic waves is developed. Based on this, the former vision of Langmuir turbulence energy thermalization via stochastic plasma electron acceleration (Erofeev 2010 J. Fusion Energy29, 337) is adapted to weakly turbulent plasmas in which this three-wave process occurs. Respective analysis of wave energy dissipation is extended to account for previously unrecognized terms in the kinetics of plasma electrons. It is stated that, cumulatively, these terms do not lead to substantial changes in the picture of Langmuir turbulence dissipation in the corresponding nonlinear plasma.

In this work we outline an approach to the problem of local equilibrium in non-axisymmetric configurations that adheres closely to Miller's original method for axisymmetric plasmas (Miller et al. 1998 Phys. Plasmas5, 973). Importantly, this method is novel in that it allows not only specification of 3D shape, but also explicit specification of the shear in the 3D shape. A spectrally-accurate method for solution of the resulting nonlinear partial differential equations is also developed. We verify the correctness of the spectral method, in the axisymmetric limit, through comparisons with an independent numerical solution. Some analytic results for the two-dimensional case are given, and the connection to Boozer coordinates is clarified.

A large-amplitude plasma beat-wave driven by two lasers (differing in frequencies equal to the plasma frequency) can accelerate the plasma electrons to a higher energy level. As the plasma beat-wave grows, it becomes susceptible to oscillating two-stream instability. The decayed sideband plasma wave couples with the pump wave to divert its energy by the instability, and saturates it. The saturated amplitude of the plasma beat-wave traps the electrons more effectively to accelerate them to higher energy. The saturation of plasma beat-wave amplitude is shown to have a significant effect in an electron energy gain.

This paper presents an explicit proof that, in the kinetic magnetohydrodynamics framework, the squared frequencies of normal-mode perturbations about a static equilibrium are real. This proof is based on a quadratic form for the square-integrable normal-mode eigenfunctions and does not rely on demonstrating operator self-adjointness. The analysis is consistent with the quasineutrality condition without involving any subsidiary constraint to enforce it, and does not require the assumption that all particle orbits be periodic. It applies to Maxwellian equilibria, spatially bounded by either a rigid conducting wall or by a plasma-vacuum interface where the density goes continuously to zero.

The nonlinear propagation of dust ion-acoustic (DIA) waves in a unmagnetized collisionless degenerate dense plasma (containing degenerate electron and positron, and classical ion fluids) has been theoretically investigated. The K-dV equation has been derived by employing the reductive perturbation method and by taking into account the effect of different plasma parameters in plasma fluid. The stationary solitary wave solution of K-dV equation is obtained, and numerically analyzed to identify the basic properties of DIA solitary structures. It has been shown that depending on plasma parametric values, the degenerate plasma under consideration supports compressive or rarefactive solitary structures. It has been also found that the effect of pressures on electrons, ions, and positrons significantly modify the basic features of solitary waves that are found to exist in such a plasma system. The relevance of our results in astrophysical objects such as white dwarfs and neutron stars, which are of scientific interest, is discussed briefly.

We construct the model of a quantum spherically symmetric plasma structure based on radial oscillations of ions. We suppose that ions are involved in ion-acoustic plasma oscillations. We find the exact solution of the Schrödinger equation for an ion moving in the self-consistent oscillatory potential of an ion-acoustic wave. The system of ions is secondly quantized and its ground state is constructed. Then, we consider the interaction between ions by the exchange of an acoustic wave. It is shown that this interaction can be attractive. We describe the formation of pairs of ions inside a plasma structure and demonstrate that such a plasmoid can exist in a dense astrophysical medium corresponding to the outer core of a neutron star (NS).

There was an error made in the name of the author in the above published article. The fourth author's name should have appeared as ‘D. P. Potapenko’. This error has now been rectified in the original article.