Dust charging processes involving the collection of electrons and positive/negative ions in a non-equilibrium dusty plasma are revisited by employing the power-law kappa (κ)-distribution function. In this context, the current balance equation is solved to obtain dust grain surface potential in the presence of negative ions. Numerically, it is found that plasma parameters, such as the κ spectral index, the negative ion-to-electron temperature ratio (γ), the negative–positive ion number density ratio (α), and the negative ion streaming speed (U0) significantly modify the dust grain potential profiles. In particular, for large kappa values, the dust grain surface potential reduces to the Maxwellian case, and at lower kappa values the magnitude of the negative dust surface potential increases. An increase in γ and U0 leads to the enhancement of the magnitude of the dust grain surface potential, while α leads to an opposite effect. The relevance of present results to low-temperature laboratory plasmas is discussed.

The properties of non-planar (cylindrical and spherical) dust-acoustic solitary waves (DA SWs) and double layers (DLs) in an unmagnetised collisionless four-component dusty plasma, whose constituents are positively and negatively charged dust grains, super thermal electrons and Boltzmannian ions are investigated by deriving the modified Gardner (MG) equation. The well known reductive perturbation method is employed to derive the MG equation and solve it numerically to study the nonlinear features of the finite amplitude non-planar DA Gardner solitons (GSs) and DLs, which are shown to exist for κ around its critical value κc (where, κ is the super thermal parameter and κc is the value of κ corresponding to the vanishing of the nonlinear coefficient of the Korteweg-de Vries (K-dV) equation). It is seen that the properties of non-planar DA SWs and DLs are significantly differs in non-planar geometry from planar geometry. It is also found that the magnitude of the amplitude of positive and negative GSs decreases with κ and the width of positive and negative GSs increases with the increase of κ.

A simple expression for the effective ion-neutral collision frequency in weakly ionized drifting plasmas of helium, neon, and argon is suggested. This expression can be useful for practical estimations related to the problems of particle charging and ion drag force in complex (dusty) plasmas.

In this paper, we investigate a mathematical model for electric arcs. The model is based on the equations of magnetohydrodynamics, where the flow and heat transfer in a plasma is coupled to electrodynamics. Our approach neglects convection and yields a reaction–diffusion model that includes only the core phenomena of electric arcs: Ohmic heating and nonlinear electric conductivity. The equations exhibit interesting mathematical properties like non-unique steady states and instabilities that can be linked to electric arc properties. Additionally, a 3D axisymmetric simulation of the creation and extinction of an electric arc is presented based on a strongly coupled numerical algorithm for the non-convective model. The approach is especially suited for high-current arcs where strong coupling becomes necessary.

A relativistically hot electron, positron and ion (e–p–i) plasma relaxes to a triple curl Beltrami (TCB) field. The TCB field being the superposition of three Beltrami fields is characterized by three scale parameters and hence there exist multiscale structures in the system. It is shown that temperatures of the plasma constituents strongly affect the scale parameters. Generally, the scale parameters associated with the TCB field may be a combination of real and complex roots. The numerical results show that for given Beltrami parameters, an increase in the thermal energy of plasma particles could transform the real eigenvalues to complex ones. It is also observed that one component is more strongly affected relative to other components on increasing temperatures of plasma species. Two different vortices become the same at higher thermal energies. This suggests that it is possible to create high β (kinetic to magnetic pressure ratio) and fully diamagnetic plasma configurations. The study has a potential relevance to space, astrophysics and laboratory plasmas.

In this paper we analyzed different measures, characterizing the melting of Lennard–Jones solid, and associated with the properties of both the translational and the orientational local order. It has been shown that the most sensitive indicator of melting is the cumulant of the probability distribution function over w6 bond-order parameter. The criterion of melting based on the indicator is proposed; the criterion can be used for any solids, having fcc/hcp types of symmetry.

In a magnetized plasma containing charged dust whose motion is magnetized, one of the fundamental collective modes that could occur is the electrostatic dust cyclotron (EDC) wave with frequency near the dust cyclotron frequency. The EDC wave propagates nearly perpendicular to the magnetic field with a small parallel wave number, so that it can be driven unstable by ion flow along the magnetic field. Because unstable parallel wavelengths can be relatively large, this places constraints on the plasma device size. In this paper, we use linear kinetic theory to investigate the excitation of higher harmonic EDC waves that have wavelengths smaller than that of the fundamental mode. Collisions of charged particles with neutrals and Coulomb collisions including dust–dust collisions are taken into account. Constraints on possible parameter ranges arising from collisional effects or from requiring stability of other waves are discussed. Numerical results are presented for possible sets of laboratory dusty plasma parameters.

It is pointed out that the Okuda–Dawson mode can couple with the newly proposed current-driven wave. It is also shown that the Shukla–Varma mode can couple with these waves if the density inhomogeneity is taken into account in a plasma containing stationary dust particles. A comparison of several low-frequency electrostatic waves and instabilities driven by shear current and shear plasma flow in an electron–ion plasma with and without stationary dust is also presented.

By using some physical approximations, distribution functions of spatial derivatives of components of an electric ionic microfield in plasmas have been theoretically evaluated. The particles are considered quasistatic. Only interactions between charged emitter and perturber ions are taken into account. Our theoretical results have been compared with those found in the literature. The few differences found are discussed. Some properties of distribution functions of spatial derivatives have been deduced from curves.

A reconsideration is made on the basic concepts of the individual photon, including its angular momentum (spin) and a possibly existing very small rest mass. In terms of conventional classical theory, as well as of its quantum mechanical counterpart, the results from a so far established Standard Model of an empty vacuum state are not found to be reconcilable with an experimentally relevant photon model. The main properties of such a model would on the other hand become compatible with the results of a recently established revised quantum electrodynamic theory based on a non-zero electric field divergence in the vacuum and a corresponding symmetry breaking of the electromagnetic field.

Geometric algebra (GA) is a recent broad mathematical framework incorporating synthetic and coordinate geometry, complex variables, quarternions, vector analysis, matrix algebra, spinors, tensors, and differential forms. It has been claimed to be a unified language for physics. GA is presented in the context of the Maxwell-Plasma system. In this formalism the divergence and curl differential operators are united in a single vector derivative, which is invertible, in the form of a first-order Green function. The four Maxwell equations can be combined into a single equation (for homogeneous and constant media) or into two equations involving the invertible vector derivative for more complex media. GA is applied to simple examples to illustrate the compactness of the notation and coordinate-free computations.

A nonlinear simulation of the E × B drifting electron laser (DEL) and the free-electron laser (FEL), in three dimensions, is presented for a prebunched electron beam to study efficiency enhancement. For the planar wiggler with flat pole faces, prebunching considerably shortens the saturation length, which favors the DEL compared to the FEL. Operation of the DEL with the planar wiggler with parabolic pole faces was not found to be possible due to the modulation of the E × B drift by the wiggler. However, simulation results of the FEL with this type of wiggler are reported.

Simple wire models have been proposed to simulate magnetic configurations in tokamaks. Here we consider electric currents in five parallel infinite wires to obtain double-null magnetic surfaces with specific choices of magnetic axis positions, triangularity, and elongation. As an example, we choose the position and the electric current of each wire to obtain magnetic surfaces similar to those expected in the tokamak international thermonuclear experimental reactor. Moreover, we also integrate the perturbed field line differential equation to simulate chaotic layers near the hyperbolic points and deposition patterns at the divertor plate observed in tokamaks. To simulate that, we add to the model a perturbing error field, due to asymmetries in the tokamak coils, and introduce a random collisional term to the field line mapping to reproduce escape pattern alterations due to particle collisions.

In this paper the spatial and temporal evolution of pulsed plasma sheath around a micropatterned surface is investigated using two-dimensional fluid model. The simulation region is considered as a micro-sized tip with rectangular cross section. The effects of rise time on electric field, ion density distributions, and dose of ions impacting the target are studied. It is shown that the plasma sheath has a balloon-like behavior in the early time stages.

In this paper, the effect of resonant helical magnetic field (RHF) and cold biased local limiter on plasma current, loop voltage, confinement time energy, poloidal beta, line emission intensity Hα, and magnetohydrodynamic (MHD) behavior based on Mirnov oscillations in the IR-T1 tokamak has been investigated. The experiments have been done in different regimes as cold biased local limiter, magnetic perturbation application, and both of these. At first the effect of the positive and negative bias voltage on plasma parameters and magnetic fluctuations detected by Mirnov coils has been investigated. Also, the effects of RHF on plasma parameters have been investigated in the edge region. Then the effects of applied biasing and RHF at the same time are analyzed. The bias voltage has been restricted to (−320 ≤ Vbias ≤ +320) and it has been applied with the limiter biasing that is fixed at r = 11.25 cm. These parameters have been measured using a diamagnetic loop, spectrometer, which is a visible light spectrometer for H-alpha, and Mirnov coils. The time-resolved frequency component analysis has been performed using short-time Fourier transforms. Fourier-based techniques and auto-correlation have been employed to analyze the frequency of MHD fluctuations. The results show that applied radial electric field at the plasma edge could control electromagnetic instabilities in the tokamak. In the positive biased regime, the amplitude of low-frequency Mirnov oscillations (<30 kHz) decreases after the application of biasing. Confinement time increases and line emission intensity decreases in all situations. The results are reversed when negative biasing has been applied. When RHF and biasing are applied to the plasma at the same time, the plasma parameters do not change any more compared to corresponding discharges with only RHF (L = 3). In other words, the amplitude of MHD activity can be totally controlled when a convenient biasing is applied to the limiter in the phases of current flat-top.

This paper investigates the modulational instability of a linearly polarized ultra-intense laser pulse propagating in electron–positron plasmas. Based on the wave equation, which contains vacuum polarization and magnetization effects, the nonlinear dispersion relation and the growth rate of instability are obtained and the effects of plasma number density and laser intensity on the growth rate are analyzed. Numerical results show that if the laser intensity is high enough, the modulational instability growth rate induced by vacuum polarization and magnetization nonlinearity can dominate the modulational instability growth rate induced by the nonlinearity associated with a relativistic effect and ponderomotive force.

The post-pinch generation of electron beam in a low energy Mather-type plasma focus (PF) device has been investigated. A fast-calibrated Rogowski coil was used to monitor the emission of electron beam. A two-channel diode X-ray spectrometer along with suitable filters provided the records of energy spectrum of X-ray radiation. Single time-period emissions of electron beam with duration of 100 to 20 ns were recorded in the high range of the device operating pressure (0.8–2 mbar). However, in the low range regime (0.2–0.8 mbar), occurrence of single spike electron beam with duration of 150 ± 50 ns, as well as multi-emission of electrons with duration of 400 ± 50 ns, was visible. A multi-peak of tube voltage along with multi-time-period radiation of X-rays dominated by copper lines (Cukα and Cukβ) was noticeable in the low-pressure range. The generated electron beam during the post-pinch phase of anomalous resistances is suspected to be the main source of X-ray radiation. This can also be related to the turbulence of the plasma column during the occurrence of anomalous resistances.

The non-thermal renormalization shielding effects on the elastic electron–atom collision process are investigated in partially ionized generalized Lorentzian non-thermal plasmas. The eikonal analysis for the Hamilton–Jacobi solution and impact parameter method are employed to obtain the eikonal scattering phase shift and eikonal cross section as functions of the collision energy, Debye length, impact parameter, and spectral index of the Lorentzian plasma. It is found that the non-thermal renormalization shielding effect enhances the eikonal scattering phase shift as well as the eikonal collision cross section, especially for small impact parameter domains. It is also found that the non-thermal renormalization shielding effect on the eikonal scattering phase shift decreases with an increase of the impact parameter. In addition, it is found that the maximum position of the eikonal collision cross section has receded from the collision center with an increase of the non-thermal character of the plasma.