Collisionless magnetic reconnection via tearing instability in non-relativistic electron–positron (pair) plasma with an anisotropic pressure is investigated. The equilibrium magnetic field is considered to be sheared force-free, and a set of linearized collisionless Magnetohydrodynamics equations describes the evolution of reconnection dynamics. A linear analytical analysis, based on scaling, demonstrates that in such a pair plasma, breaking the frozen in flow constraint for field lines can be mainly provided by the non-gyrotropic pressure of electrons and positrons (rather than the particle bulk inertia) when the current sheet width is smaller than the particle Larmor radius (Δx < rL). This condition is satisfied when β > d2 (d = c/ωp is the particle skin-depth with the electron/positron frequency ωp and β = 8πP(0)/B02 ⪡ 1). Meanwhile, on top of the Lorentz force and in the absence of the reconnection facilitating mechanism of the Hall effect, non-scalar pressure force can accelerate bulk plasma into the diffusion region at the scale lengths of the order of dx. Therefore, the respective regime of tearing instability proceeds much faster compared with the case of an isotropic pressure with a new dimensionless growth rate of (γτA) ~ d.

The effect of the electrostatic confinement potential on electron number densities and electron temperatures under bi-Maxwellian approximation for electron distribution function has been studied in an electrostatically plugged multi-dipole argon plasma system. Electrostatic plugging is implemented by biasing the electrically isolated multi-dipole magnetic cage. Experimental results show that the density ratio (N) and temperature ratio (T) of the two electron groups can be controlled by changing the voltage applied to the magnetic cage. Out of the two groups of electrons, one group has the cold electrons, which are plasma electrons produced by the ionization process, and the other group has the hot primary electrons.

Using the multi-fluid model of plasmas, we have analytically obtained a generalized Bohm criterion in the plasma, including hot electrons and multiply charged ions, and have numerically examined its validity. The new Bohm-sheath criterion shows that increasing the charge number of positive ions and decreasing the charge number of negative ions would increase the minimum ion speed that is required for the Bohm criterion to satisfy.

The production of aluminium and zinc plasmas for the deposition of coatings upon steel strip is monitored by optical emission spectroscopy measurements. The plasma is created from an inductive source. The atom and the ion densities as well as the electron temperature are obtained such that the plasma can be characterized. It will be shown that the obtained plasmas are typically highly ionized and deviate from thermal equilibrium.

The hydrodynamic equations of positive and negative ions, degenerate electrons, and the Poisson equation are used along with the reductive perturbation method to derive the three-dimensional Zakharov–Kuznetsov (ZK) equation. The G′/G-expansion method is used to obtain a new class of solutions for the ZK equation. At certain condition, these solutions can describe the solitary waves that propagate in our plasma. The effects of negative ion concentrations, the positive/negative ion cyclotron frequency, as well as positive-to-negative ion mass ratio on solitary pulses are examined. Finally, the present study might be helpful to understand the propagation of nonlinear ion-acoustic solitary waves in a dense plasma, such as in astrophysical objects.

High-speed imaging is a powerful tool for studying dusty plasmas. The recorded trajectories of dust particles can provide direct information about the physical processes involved in dust-plasma and dust–dust interactions. A review of some experiments and their imaging techniques employed for tracking dust particles immersed in low-ionized gases and in high-density plasma jets is presented. Digital cameras are used to record the motion of slow or hypervelocity dust particles dragged by plasma jets, or to evidence single or collective dust particle oscillations and vibrations in the plasma sheath.

The coupled drift-ion acoustic (DIA) waves in an inhomogeneous magnetoplasma having negative and positive ions can be driven by the parallel sheared flows in the presence of Cairns distributed non-thermal electrons. The coupled DIA waves can become unstable due to shear flows. The conditions of modes instability are discussed with effects of non-thermal electrons. These are the excited modes and start interactions among themselves. The interaction is governed by the Hasegawa–Mima equations with analytical solutions in the form of a vortex chain and dipolar vortex. On the other hand, for scalar nonlinearity the Kortweg deVries-type equation is obtained with solitary wave solution. Possible application of the work to the space and laboratory plasmas are highlighted.

We present a theoretical model for the generation of coherent gamma rays by a free electron laser, where a high-energy electron beam interacts with an electromagnetic wiggler. By replacing the static undulator with a 1-μm laser wiggler, the resulting radiation would go from X-rays currently observed in experiments, to gamma rays. Coherent light in the gamma-ray range would have wide-ranging applications in the probing of matter on sub-atomic scales.

Properties of the coupled dust ion-acoustic drift wave instability in a radially bounded dusty magnetoplasma with an equilibrium sheared parallel ion (SPI) flow are investigated. By using the two-fluid model for the electrons and ions, a wave equation for the low-frequency coupled dust ion-acoustic drift waves in a bounded plasma with stationary charged dust grains is derived. The wave equation admits a linear dispersion relation, which exhibits that the radial boundary affects the growth rate of the coupled ion-acoustic drift wave instability which is excited by the SPI flow. The results should be relevant to dusty magnetoplasma experiments with an SPI flow.

We present a particle-in-cell code accounting for the magnetic dipole force and for the magnetization currents associated with the electron spin. The electrons are divided into spin-up and spin-down populations relative to the magnetic field, where the magnetic dipole force acts in opposite directions for the two species. To validate the code, we study wakefield generation by an electromagnetic pulse propagating parallel to an external magnetic field. The properties of the generated wakefield are shown to be in good agreement with previous theoretical results. Generalizations of the code to account for other quantum effects are discussed.

Under a study contracted by GEN3 Partners, spectra of high current pinch discharges in pure hydrogen and helium were recorded in the extreme ultraviolet radiation region at the Harvard Smithsonian Center for Astrophysics (CfA) in an attempt to reproduce experimental results published by BlackLight Power, Inc. (BLP) showing predicted continuum radiation due to hydrogen in the 10–30 nm region (Mills, R. L. and Lu, Y. 2010 Hydrino continuum transitions with cutoffs at 22.8 nm and 10.1 nm. Int. J. Hydrog. Energy35, 8446–8456, doi:10.1016?j.ijhydene.2010.05.098). Alternative explanations were considered to the claimed interpretation of the continuum radiation as being that emitted during transitions of H to lower-energy states (hydrinos). Continuum radiation was observed at CfA in the 10–30 nm region that matched BLP's results. Considering the low energy of 5.2 J per pulse, the observed radiation in the energy range of about 120–40 eV, reference experiments and analysis of plasma gases, cryofiltration to remove contaminants, and spectra of the electrode metal, no conventional explanation was found in the prior or present work to be plausible including contaminants, electrode metal emission, and Bremsstrahlung, ion recombination, molecular or molecular ion band radiation, and instrument artifacts involving radicals and energetic ions reacting at the charge-coupled device and H2 re-radiation at the detector chamber. Moreover, predicted selective extraordinarily high-kinetic energy H was observed by the corresponding Doppler broadening of the Balmer α line.

A general formalism for calculating the potential distribution Φ(z) in the quasineutral region of a new class of plane Tonks–Langmuir (TL)-type bounded-plasma-system (BPS) models differing from the well-known ‘classical’ TL model (Tonks, L. and Langmuir, I. 1929 A general theory of the plasma of an arc. Phys. Rev. 34, 876) by allowing for arbitrary (but still cold) ion sources and arbitrary electron distributions is developed. With individual particles usually undergoing microscopic collision/sink/source (CSS) events, extensive use is made here of the basic kinetic-theory concept of ‘CSS-free trajectories’ (i.e., the characteristics of the kinetic equation). Two types of electron populations, occupying the ‘type-t’ and ‘type-p’ domains of electron phase space, are distinguished. By definition, the type-t and type-p domains are made up of phase points lying on type-t (‘trapped’) CSS-free trajectories (not intersecting the walls and closing on themselves) and type-p (‘passing’) ones (starting at one of the walls and ending at the other). This work being the first step, it is assumed that ε ≡ λD/l → 0+ (where λD and l are a typical Debye length and a typical ionization length respectively) so that the system exhibits a finite quasineutral ‘plasma’ region and two infinitesimally thin ‘sheath’ regions associated with the ‘sheath-edge singularities’ | dΦ/dz|z→±zs → ∞. The potential in the plasma region is required to satisfy a plasma equation (quasineutrality condition) of the form ni {Φ} =ne (Φ), where the electron density ne (Φ) is given and the ion density ni {Φ} is expressed in terms of trajectory integrals of the ion kinetic equation, with the ions produced by electron-impact ionization of cold neutrals. While previous TL-type models were characterized by electrons diffusing under the influence of frequent collisions with the neutral background particles and approximated by Maxwellian (Riemann, K.-U. 2006 Plasma-sheath transition in the kinetic Tonks–Langmuir model. Phys. Plasmas 13, 063508) or bi-Maxwellian (Godyak, V. A. et al. 1995 Tonks–Langmuir problem for a bi-Maxwellian plasma. IEEE Trans. Plasma Sci. 23, 728) electron velocity distribution functions (VDFs), which satisfy the zero-CSS-term (Vlasov) kinetic equation and imply zero electron currents, we here propose a more general class of electron VDFs allowing, in an approximate manner, for non-zero CSS terms and finite electron currents inside the plasma region. The sheath-edge and floating-wall potentials are calculated by balancing the ion and electron current densities at sheath-edge singularities. In a first detailed application, the type-t and type-p electron VDFs are assumed to be ‘inner’ and ‘outer’ cut-off Maxwellians respectively, with different amplitudes and ‘formal’ temperatures, implying the perfectly CSS-free limit. For the special case of equal type-t and type-p electron VDF amplitudes and formal temperatures, the classical Boltzmann distribution for electrons is formally retrieved. Special cases with other amplitude and formal-temperature ratios show significant deviations from the classical case.

The properties of non-planar (cylindrical and spherical) ion acoustic solitary waves (IASWs) in an unmagnetized collisionless electron-positron-ion (e-p-i) plasma, whose constituents are inertial ions and superthermal/non-Maxwellian electrons and positrons (represented by the kappa (κ) distribution), are investigated by deriving the modified Gardner (MG) equation. The well-known reductive perturbation method is employed to derive the MG equation. The basic features of non-planar IA Gardner solitons (GSs) are discussed. It is seen that the properties of non-planar IAGSs (positive and negative) differ significantly as the value of spectral index kappa changes.

A self-consistent model for the description of dusty plasma structures, such as noctilucent clouds (NLC) and polar mesosphere summer echoes (PMSE), which are frequently grouped together under the common term polar mesospheric clouds, is presented. The model takes into account the processes of condensation of water vapor, ionization, recombination, action of solar radiation, sedimentation, dust particle growth, dust particle charging, electric fields, etc. Using the model, we explain the basic data of observations on the behavior of charged component in polar summer mesosphere. Furthermore, we show the influence of initial distributions of fine particles as well as that of the processes of condensation and water molecule absorption by fine particles on the formation of NLC and PMSE. We also illustrate the possibility of the formation of layered structure and sharp boundaries of NLC.

Numerical simulations have been conducted to study the spatial growth rate and emission topology of the cyclotron-maser instability responsible for stellar/planetary auroral magnetospheric radio emission and intense non-thermal radio emission in other astrophysical contexts. These simulations were carried out in an unconstrained geometry, so that the conditions existing within the source region of some natural electron cyclotron masers could be more closely modelled. The results have significant bearing on the radiation propagation and coupling characteristics within the source region of such non-thermal radio emissions.

The nonlinear solitary and freak waves in a plasma composed of positive and negative ions, superthermal electrons, ion beam, and stationary dust particles have been investigated. The reductive perturbation method is used to obtain the Korteweg-de Vries (KdV) equation describing the system. The latter admits solitary wave solution, while the dynamics of the modulationally unstable wavepackets described by the KdV equation gives rise to the formation of freak/rogue excitation described by the nonlinear Schrödinger equation. In order to show that the characteristics of solitary and freak waves are influenced by plasma parameters, relevant numerical analysis of appropriate nonlinear solutions are presented. The results from this work predict nonlinear excitations that may associate with ion jet and superthermal electrons in Herbig–Haro objects.

Surface plasmons (SP) in a semi-bounded quantum plasma with degenerate electrons (e.g. a metal) are considered, and some interesting consequences of electron Pauli blocking for the SP dispersion and temporal attenuation are discussed. In particular, it is demonstrated that a semi-bounded degenerate plasma with a sharp boundary supports two types of SP with distinct frequencies and qualitatively different temporal attenuation, in contrast to a non-degenerate hot plasma that only supports one type of SP.

A stimulated Raman scattering (SRS) on electron plasma waves in underdense plasmas is of a big concern in laser fusion due to an energy loss and target preheating. Complex features of large Backward-SRS (BRS) in experiments and simulations with laser fusion targets are found. Recently, to reach ultra-high intensities at multi-exawatts and beyond, relevant to high-energy physics, Raman amplification based on BRS was proposed; still, with high sensitivity and a narrow operational window. Firstly, we revisit a standard three-coupled mode model of BRS to show that the condition for an absolute instability is readily satisfied in uniform plasmas which excites large Raman signals from a background noise. It sets in for interaction length L0 shorter than, both, the plasma length L and absorption length La. Further, we point out a generic BRS feature, which due to a nonlinear frequency shift in large electron plasma wave (relativistic/trapping effects), instead to a steady state, saturates via intermittent pulsations with incoherent spectral broadening. A ‘break up’ of Manley–Rowe invariants is shown to predict non-stationary BRS. Finally, an intermediate intensity regime is originally proposed for coherent femto-second pulse generation in a thin exploding foil plasma, with scalings investigated by theory and particle simulations.

By investigating the dielectric response of the Fermi–Dirac plasma in the linear limit and evaluating the electrostatic potential around the positive stationary test charge, we find that the Shukla–Eliasson attractive force is present for the plasma density range expected in the interiors of large planets for a wide range of plasma atomic number. This research, which is based on the generalized electron Fermi-momentum, further confirms the existence of the newly discovered Lennard-Jones-like attractive potential and its inevitable role in plasma crystallization in the cores of planets. Moreover, it is observed that the characteristics of the attractive potential are strongly sensitive to the variation of plasma density and composition. Current research can also have applications in the study of strong laser-matter interactions and inertially confined plasmas.

In this paper, the theoretical analysis regarding potential structure on the inertial electrostatic confinement fusion devices has been carried out. Negatively biased grid as cathode placed at the center of the device surrounded by anode is assumed. The device is an ion-injection system and electrons may be emitted from the surface of the cathode. So the existence of both ion and electron currents inside the cathode is considered. Dependence of radial potential well structure on some important parameters as the spreads in the normalized total and angular electron and ion energies, the ratio of ion circulating current to electron circulating current, ion perveance, and grid transparency are investigated by solving Poisson equation.