A necessary condition for the existence of general dissipative magneto-hydrodynamic equilibria is derived. The derivation comprises Ohm's law and the existence of magnetic surfaces, only in the sense of the Kolmogorov–Arnold–Moser (KAM) theorem. All other equations describing the system are only required for evaluating the condition for a specific case.

We present a coupling between an analytical three-dimensional model covering the plasma flow behaviour through the magnetopause transition layer near a reconnection site, with results from a global MHD simulation describing the plasma flow in the magnetosheath. The structure of the plasma flow near a reconnection site at the dayside terrestrial magnetopause is investigated, together with the development of the magnetopause transition region.

It is shown that purely growing magnetic fields in a two-component dusty plasma can e generated due to the equilibrium drift of positive and negative dust grains. For this purpose, a linear dispersion relation has been derived by using the hydrodynamic equations for the charged dust fluids, the Maxwell equation and Faraday' law. The dispersion relation admits a purely growing instability, the growth rate of which is proportional to the equilibrium streaming speeds of positive and negative dust grains. A possible physical explanation for the instability is offered. Applications of our investigation to magnetic fields in the thin Martian environments, interplanetary spaces and dense molecular clouds are mentioned.

After some 12 years as Editor of the Journal I have decided that it is time to move on and I will relinquish this position at the end of 2006. From the beginning of 2007 Padma Shukla will be the sole Editor and papers should be submitted to him or to any of the Associate Editors. The web address jpp@st-andrews.ac.uk will cease to be operative from this time. I would like to thank all those authors who have contributed to the Journal during my editorship and hope that they will continue to give it their support. I have every confidence that it will flourish under Padma's able guidance.

The use of very short high-voltage pulses combined with a dielectric layer results in high-energy electrons that dissociate oxygen molecules into atoms, which are a prerequisite for the subsequent production of ozone by collisions with oxygen molecules and third particles. The production of ozone depends on both the electrical and the physical parameters. For ozone generation by pulsed dielectric barrier discharge in oxygen, a mathematical model, which describes the relation between ozone concentration and these parameters that are of importance in its design, is developed according to dimensional analysis theory. A formula considering the ozone destruction factor is derived for predicting the characteristics of the ozone generation, within the range of the corona inception voltage to the gap breakdown voltage. The trend showing the dependence of the concentration of ozone in oxygen on these parameters generally agrees with the experimental results, thus confirming the validity of the mathematical model.

The turbulence acceleration of ultra-relativistic electrons by strong Langmuir plasmons is analytically studied in a laser-plasma. Based on the Fokker–Planck equation in the frame of strong turbulence, the exponential form of the spectra of hot electrons is obtained theoretically, which is consistent with the experimental result near the critical surface in a laser-plasma.

We consider the nonlinear interactions between upper-hybrid (UH) and Alfvén modes in a magnetized electron–ion plasma containing a fraction of stationary charged dust grains. The interaction is governed by a pair of equations for the UH wave envelope including the relativistic electron mass increase and the density and compressional magnetic field fluctuations associated with the Alfvén modes that are, in turn, driven by the ponderomotive force of the UH waves. The coupled mode equations are then Fourier analyzed to obtain a new dispersion relation, which admits new classes of modulational instabilities. The existence of a cusp-shaped UH envelope soliton is also predicted. The result can have relevance to the electron acceleration by sharply localized UH waves in the dusty magnetosphere of Saturn.

A new configuration for the laser accelerator is proposed, which is inspired by the relativistic photon mirror effect. The material mirror is replaced here by an intense laser pulse, acting as a photon mirror for the incoming charged particles. A sufficient condition for particle reflection at such a photon mirror is established and three types of particle trajectories are described. A snow-plow acceleration regime is identified and quantitatively defined. Production of intense radiation bursts by the charged particle beam during the reflection process is also demonstrated.

An improvement of an existing three-dimensional analytical model describing the solar wind flow near a reconnection site at the dayside magnetopause is reported. Introducing an arbitrary orientation of the reconnection line, general solutions for the plasma velocity and magnetic field during the transition of the magnetopause are presented, together with the development of the magnetopause transition layer away from the reconnection site.

We report on a comparison of high-resolution numerical simulations of Lagrangian particles advected by incompressible turbulent hydro- and magnetohydrodynamic (MHD) flows. Numerical simulations were performed with up to 10243 collocation points and 10 million particles in the Navier–Stokes case and 5123 collocation points and 1 million particles in the MHD case. In the hydrodynamics case our findings compare with recent experiments from Mordant et al. (2004 New J. Phys.6, 116) and Xu et al. (2006 Phys. Rev. Lett.96, 024503). They differ from the simulations of Biferale et al. (2004 Phys. Rev. Lett.93, 064502) due to differences of the ranges chosen for evaluating the structure functions. In Navier–Stokes turbulence intermittency is stronger than predicted by the multifractal approach of Biferale et al. (2004 Phys. Rev. Lett.93, 064502) whereas in MHD turbulence the predictions from the multifractal approach are more intermittent than observed in our simulations. In addition, our simulations reveal that Lagrangian Navier–Stokes turbulence is more intermittent than MHD turbulence, whereas the situation is reversed in the Eulerian case. Those findings can not consistently be described by the multifractal modeling. The crucial point is that the geometry of the dissipative structures have different implications for Lagrangian and Eulerian intermittency. Application of the multifractal approach for the modeling of the acceleration probability density functions works well for the Navier–Stokes case but in the MHD case just the tails are well described.

The effects of density and temperature on a surface electron-acoustic plasma wave are investigated in a semi-bounded dusty plasma of two-temperature electrons. The dispersion relation of the surface electron-acoustic plasma wave is obtained by the plasma dielectric function with the specular reflection boundary condition. The phase velocity is found to be decreased when increasing the ratio of the temperature of hot electrons to that of cold electrons for large wave numbers. It is also found that the phase velocity increases with an increase in the ratio of the density of hot electrons to that of cold electrons and that the phase velocity of the surface electron-acoustic wave increases with an increase in the density of the dust grains.

It is shown that equilibrium polaritonic flows can amplify magnetic fields in an ultra-cold quantum electron–positron/hole (polaritons) plasma. For this purpose, a linear dispersion relation has been derived by using the quantum generalized hydrodynamic equations for the polaritons, the Maxwell equation, and Faraday's law. The dispersion relation admits purely growing instabilities, the growth rates of which are proportional to the equilibrium streaming speeds of the polaritons. Possible applications of our work to the spontaneous excitation of magnetic fields and the associated cross-field transport of the polaritons in micromechanical systems, compact dense astrophysical objects (e.g. neutron stars), and intense laser–plasma interaction experiments are mentioned.

We consider a kinetic modulational instability of broadband (random phase) magnetic-field-aligned circularly polarized dispersive Alfvén waves in plasmas. By treating random phase Alfvén waves as quasi-particles, we consider their nonlinear interactions with ion quasi-modes within the framework of the wave-kinetic and Vlasov descriptions. A nonlinear dispersion relation governing such interactions is derived and analyzed. An explicit expression for the kinetic modulational instability growth rate is presented. Our results can be of relevance to the nonlinear propagation of incoherent Alfvén waves, which have been frequently observed in interstellar media, in the solar corona and in the solar wind, as well as in the foreshock regions of planetary bow-shocks and laboratory plasmas.

Stars are formed as a result of the gravitational (Jeans) collapse of dense clumps in interstellar clouds. These clouds are partially ionized by nearby ionizing sources. We investigate the gravitational instability in such molecular clouds considering the non-Boltzmannian distribution for electrons and ions, which is more realistic than the Boltzmannian distribution. Assuming the perturbation (fluctuation) response in a radial direction as a mathematical analogue of the x-direction in the plane geometry approximation in the form f ∼ exp(ikx–iωt), the equations of motion for different species of the multi-fluid plasma are linearized. Jeans' swindle is used as a local approximation for the equilibrium and the dispersion relation is derived by usual normal mode analysis. Then, an analytical solution to the dispersion equation with an explanation of the effects on star formation is given.

The influence of an ergodic magnetic limiter (EML) on plasma turbulence is investigated in the Tokamak Chauffage Alfvén Brésilien (TCABR), a tokamak with a peculiar natural superposition of the electrostatic and magnetic fluctuation power spectra. Experimental results show that the EML perturbation can reduce both the magnetic oscillation and the electrostatic plasma turbulence. Whenever this occurs, the turbulence-driven particle transport is also reduced. Moreover, a bispectral analysis shows that the nonlinear coupling between low- and high-frequency electrostatic fluctuations increases significantly with the EML application.

The reversed magnetic shear is the most important factor in the study of the plasmas of a tokamak. In this paper we focus our research, as a first stage, on the control of the improved confinement regimes by studying the influence of the reversed shear on its quality in the plasma of a tokamak and especially in reducing the anomalous transport in ITER. Then we study the influence of the perturbation modes on the particle diffusion. At the end, a comparison between simulation results obtained using ITER and TEXT parameters is carried out.

The resonant coupling between Alfvén waves is reconsidered. New results are found for cold magnetoplasmas where temperature effects are negligible.

We present a new formulation for the direct laser acceleration of electrons in vacuum based on the Hamiltonian theory. Two different regimes for the snow-plowed, accelerated electrons are identified and characterized, the first pertaining to high-intensity and the second to low-intensity pulses, both leading to efficient electron acceleration. Particle energy yields are shown to be independent of the exact shape of the laser pulse and energy gains are estimated.

Although the harmonics generated when intense laser light interacts with solid targets are broadly understood in terms of their dependence on the incident intensity, less attention has been paid to the ways in which their behaviour depends on plasma density. In this paper the conversion efficiencies of the odd harmonics generated when light is incident normally on the target surface are shown to be strongly resonant in character. The number of resonances is governed by harmonic order and their behaviour with density is further complicated by Langmuir wave emission at the corresponding plasma resonant densities for successive harmonic orders. Only at densities well above these resonances does the emission decay monotonically with density. The density dependence predicted by theory is confirmed by particle-in-cell simulations.

Magnetohydrodynamic wave interactions in a linear shear flow are investigated using the Lagrangian fluid displacement ξ and entropy perturbation Δ S, in which a spatial Fourier solution is obtained in the frame of the background shear flow (Kelvin's method). The equations reduce to three coupled oscillator equations, with time-dependent coefficients and with source terms proportional to the entropy perturbation. In the absence of entropy perturbations, the system admits a wave action conservation integral consisting of positive and negative energy waves. Variational and Hamiltonian forms of the equations are obtained. Examples of wave amplification phenomena and sharp resonant-type wave interactions are obtained. Implications for the interaction of magnetohydrodynamic waves in the shear flow between fast, polar coronal-hole solar wind and slow, streamer belt solar wind are discussed.