Exact nonlinear (arbitrary amplitude) wave-like solutions of an incompressible, magnetized, non-dissipative two-fluid system are found. It is shown that, in 1-D propagation, these fully nonlinear solutions display a rare property; they can be linearly superposed.

We investigate the drift dissipative instability in a non-uniform magnetized plasma composed of electrons, positive ions, negative ions and negatively charged dust particles. We use a multi-fluid plasma model and derive a dispersion relation for the electrostatic drift waves with frequencies much smaller than the ion gyrofrequencies and wavelengths longer than the ion gyroradii. The presence of the negatively charged, massive dust grains affects the drift wave frequency and the growth rate of the drift dissipative instability. The present results may be relevant to space and laboratory magnetoplasmas containing negative ions and charged dust grains.

Electron and proton acceleration by a drifted super-Dreicer electric field is investigated in a strongly compressed non-neutral reconnecting current sheet (NRCS). The guiding field is assumed to be constant within a reconnecting current sheet (RCS) and parallel to the direction of the drifted electric field. The other two magnetic field components, transverse and tangential, are considered to vary exponentially and linearly with distances from the X-nullpoint. The proton and electron energy spectra are calculated numerically in a model RCS with different magnetic field topologies by solving an equation of motion in the test-particle approach with some test with a particle-in-cell (PIC) approach. Three kinds electric field generated inside a RCS are considered: a drifted electric field caused by the plasma inflows formed during a magnetic reconnection process; a polarization electric field induced by the accelerated protons and electrons; and a turbulent electric field induced by instabilities generated by accelerated particles. Electron and proton densities, and energy spectra inside a RCS and at ejection are found to be strongly affected by the magnetic field topology: for stronger magnetic fields the spectra are softer having a small higher-energy cutoff while for weaker magnetic fields the spectra are harder with much larger upper cutoff energies. Depending on the magnetic component ratios and drifted electric field magnitude, particles are found to be ejected either as quasi-thermal flows with very high temperatures or as focused power-law beams. A polarization field is found to reduce the acceleration time inside a RCS and to increase the energy gained by particles at acceleration by a pure drifted electric field by a few orders of magnitude. The turbulent electric field induced by the two beam instabilities of the same kind of particles leads to a significant increase in the number of particles with higher energies resulting in a flattening of their energy spectra.

The random walk of magnetic field lines in the presence of magnetic turbulence in plasmas is investigated from first principles. An isotropic model is employed for the magnetic turbulence spectrum. An analytical investigation of the asymptotic behavior of the field-line mean-square displacement 〈(Δx)2〉 is carried out, in terms of the position variable z. It is shown that 〈(Δx)2〉 varies as ~z ln z for large distance z. This result corresponds to a superdiffusive behavior of field line wandering. This investigation complements previous work, which relied on a two-component model for the turbulence spectrum. Contrary to that model, quasilinear theory appears to provide an adequate description of the field-line random walk for isotropic turbulence.

A new set of equations describing the coupling of high-frequency electrostatic waves with ion fluctuations is obtained taking into account a non-thermal electron distribution. It is shown that there exist stationary envelope solitons which have qualitatively different structures from the solutions reported earlier. In particular, the Langmuir field envelopes are found with similar width and strong field intensities in comparison to the isothermal case. It is also shown that the presence of the fast or non-thermal electrons significantly modifies the nature of Langmuir solitons in the transition from a single-hump solution to a double-hump solution as the Mach number increases to unity. The low-frequency electrostatic potential associated with the high-frequency Langmuir field has the usual single-dip symmetric structure whose amplitude increases with increasing Mach number. Furthermore, the dip at the center of the double-hump Langmuir soliton is found to become smaller as the proportion of non-thermal electrons increases.

A perturbative three-dimensional analysis is presented of Alfvén waves in a magnetic X-point configuration with a strong longitudinal guide field. The waves are assumed to propagate in the direction of the X-line, and both the plasma beta and equilibrium plasma current are taken to be zero. This provides a simple model of Alfvén wave propagation in the divertor region of tokamak plasmas. It is shown that the presence of the X-point places constraints on the structure of the leading-order (shear Alfvén) eigenfunctions. These eigenfunctions, and fast wave corrections to them, are determined explicitly for two cases. In the first of these the stream function for the shear Alfvén flow is azimuthally symmetric in the X-point plane and singular at the X-line; in the second case the stream function is largely confined to two quadrants in the X-point plane and is non-singular. For the latter scenario it is shown that coupling of the shear and fast waves is strongly localized to the vicinity of the separatrix.

Linear and nonlinear properties of the two-dimensional obliquely propagating dust magnetosonic wave are studied in a three-component dusty plasma. The dispersion relations in the linear and Kadomstev–Petviashvili (KP) equation in the nonlinear regime are derived for small-amplitude perturbations. It is shown that the linear dispersion properties of the low-frequency dust magnetosonic wave depend on the angle θ that the magnetic field makes with the x-axis, the ratio of ion to electron concentration, and the plasma beta. It is found that retaining the electron pressure term gives rise to novel features in the dust magnetosonic wave. The slow magnetosonic wave is found to be the damped mode and, therefore, the only propagating mode in our system is the fast magnetosonic mode. It is found that the KP equation admits compressive solitary structures. Finally, it is found that the amplitude of the soliton increases as the ratio of electron to ion concentration, p, angle θ, and the plasma beta, β, is increased.

It is shown that the energy of protons accelerated in laser–matter interaction experiments may be significantly increased through the process of splitting the incoming laser pulse into multiple interaction stages of equal intensity. From a thermodynamic point of view, the splitting procedure can be viewed as an effective way of increasing the efficiency of energy transfer from the laser light to protons, which peaks for processes having the least amount of entropy gain. It is predicted that it should be possible to achieve at least a 100% increase in the energy efficiency in a six-stage laser proton accelerator compared with a single laser–target interaction scheme.

We present an investigation for the generation of intense magnetic fields in dense plasmas with an anisotropic electron Fermi–Dirac distribution. For this purpose, we use a new linear dispersion relation for transverse waves in the Wigner–Maxwell dense quantum plasma system. Numerical analysis of the dispersion relation reveals the scaling of the growth rate as a function of the Fermi energy and the temperature anisotropy. The nonlinear saturation level of the magnetic fields is found through fully kinetic simulations, which indicates that the final amplitudes of the magnetic fields are proportional to the linear growth rate of the instability. The present results are important for understanding the origin of intense magnetic fields in dense Fermionic plasmas, such as those in the next-generation intense laser–solid density plasma experiments.

The recent analysis of large-amplitude solitary potentials in a charge varying dusty plasma with trapped dust particles (Tribeche, M. 2005 Phys. Plasmas12, 072304) is extended to include the electron trapping self-consistently. The non-isothermal trapped electron charging is investigated based on the orbit motion limited approach. It is found that the nonlinear localized potential structure enlarges when the electrons deviate from isothermality. The effect of this deviation is more significant under certain conditions. The dust particles are locally expelled and pushed out of the region of soliton localization as the electrons evolve far away from their thermodynamic equilibrium.

The usual theory of plasma relaxation, based on the selective decay of magnetic energy over the (global) magnetic helicity, predicts a force-free state for a plasma. Such a force-free state is inadequate to describe most realistic plasma systems occurring in laboratory and space plasmas as it produces a zero pressure gradient and cannot couple magnetic fields with flow. A different theory of relaxation has been proposed by many authors, based on a well-known principle of irreversible thermodynamics, the principle of minimum entropy production rate which is equivalent to the minimum dissipation rate of energy. We demonstrate the applicability of minimum dissipative relaxed states to various self-organized systems of magnetically confined plasma in the laboratory and in the astrophysical context. Such relaxed states are shown to produce a number of basic characteristics of laboratory plasma confinement systems and solar arcade structure.