We estimate the total cross sections for field-stimulated photoemissions and photoabsorptions by quasi-free electrons within a non-equilibrium plasma evolving from the strong coupling to the weak coupling regime. Such a transition may occur within laser-created plasmas, when the initially created plasma is cold but the heating of the plasma by the laser field is efficient. In particular, such a transition may occur within plasmas created by intense vacuum ultraviolet (VUV) radiation from a free-electron laser (FEL) as indicated by the results of the first experiments performed by Wabnitz at the FLASH facility at DESY. In order to estimate the inverse bremsstrahlung cross sections, we use point-like and effective atomic potentials. For ions modelled as point-like charges, the total cross sections are strongly affected by the changing plasma environment. The maximal change of the cross sections may be of the order of 75 at the change of the plasma parameters: inverse Debye length, κ, in the range κ = 0 − 3 Å−1 and the electron density, ρe, in the range ρe = 0.01 − 1 Å−3. These ranges correspond to the physical conditions within the plasmas created during the first cluster experiments performed at the FLASH facility at DESY. In contrast, for the effective atomic potentials the total cross sections for photoemission and photoabsorption change only by a factor of seven at most in the same plasma parameter range. Our results show that the inverse bremsstrahlung cross section estimated with the effective atomic potentials is not affected much by the plasma environment. This observation validates the estimations of the enhanced heating effect obtained by Walters, Santra and Greene. This is important as this effect may be responsible for the high-energy absorption within clusters irradiated with VUV radiation.

The question of magnetic field structure in the vicinity of the separatrix in divertor tokamaks is studied. The authors have investigated this problem earlier in a series of papers, using various mathematical techniques. In the present paper, the two-wire model (TWM) [Reiman, A. 1996 Phys. Plasmas3, 906] is considered. It is noted that, in the TWM, it is useful to consider an extra equation expressing magnetic flux conservation. This equation does not add any more information to the TWM, since the equation is derived from the TWM. This equation is useful for controlling the step size in the numerical integration of the TWM equations. The TWM with the extra equation is called the flux-preserving TWM. Nevertheless, the technique is apparently still plagued by numerical inaccuracies when the perturbation level is low, resulting in an incorrect scaling of the stochastic layer width. The stochastic broadening of the separatrix in the flux-preserving TWM is compared with that in the low mn (poloidal mode number m and toroidal mode number n) map (LMN) [Ali, H., Punjabi, A., Boozer, A. and Evans, T. 2004 Phys. Plasmas11, 1908]. The flux-preserving TWM and LMN both give Boozer–Rechester 0.5 power scaling of the stochastic layer width with the amplitude of magnetic perturbation when the perturbation is sufficiently large [Boozer, A. and Rechester, A. 1978, Phys. Fluids21, 682]. The flux-preserving TWM gives a larger stochastic layer width when the perturbation is low, while the LMN gives correct scaling in the low perturbation region. Area-preserving maps such as the LMN respect the Hamiltonian structure of field line trajectories, and have the added advantage of computational efficiency. Also, for a degree of freedom Hamiltonian system such as field lines, maps do not give Arnold diffusion.

Nonlinear resonant interaction between energetic particles and quasi-electrostatic wave propagating perpendicularly to the ambient magnetic field in a homogeneous plasma is studied in detail, with the main focus on the wave amplification or attenuation caused by resonant interaction. As for k∥ → 0, resonance velocity determined from linear resonance conditions tends to infinity, the interaction under discussion is a completely nonlinear phenomenon. While the wave amplitude may increase or decrease depending on the wave parameters and integral characteristics of the energetic particle distribution function, an essential wave amplification may occur when the wave frequency is close to a multiple of cyclotron harmonic, and when the transversal energy of resonant particles is large enough.

The Experimental Advanced Superconducting Tokamak (EAST) has a major radius of R0 = 1.75 m and a midplane halfwidth of 0.5 m. It has been operated with a toroidal magnetic field B0 = 2 T and Ip ≤ 500 kA. The evolution of the plasma equilibrium is analysed between discharges by Equilibrium Fitting Code (EFIT). Limiter, single-null and double-null diverted configurations have been produced. A plasma elongation in the range 1.3 ≤ κ ≤ 1.9 and a triangularity in the range 0.1 ≤ δ ≤ 0.55 have been sustained. The operation space of elongated discharges is also presented based on the EAST database.

The influence of non-monochromaticity on low-frequency, large-scale zonal-flow nonlinear generation by small-scale magnetized Rossby (MR) waves in the Earth's ionospheric E-layer is considered. The modified parametric approach is used with an arbitrary spectrum of primary modes. It is shown that the broadening of the wave packet spectrum of pump MR waves leads to a resonant interaction with a growth rate of the order of the monochromatic case. In the case when zonal-flow generation by MR modes is prohibited by the Lighthill stability criterion, the so-called two-stream-like mechanism for the generation of sheared zonal flows by finite-amplitude MR waves in the ionospheric E-layer is possible. The growth rates of zonal-flow instabilities and the conditions for driving them are determined. The present theory can be used for the interpretation of the observations of Rossby-type waves in the Earth's ionosphere and in laboratory experiments.

The model of two-fluid, axisymmetric, ambipolar magnetized plasma detachment from thruster guide fields is extended to include plasmas with non-zero injection angular velocity profiles. Certain plasma injection angular velocity profiles are shown to narrow the plasma plume, thereby increasing exhaust efficiency. As an example, we consider a magnetic guide field arising from a simple current ring and demonstrate plasma injection schemes that more than double the fraction of useful exhaust aperture area, more than halve the exhaust plume angle, and enhance magnetized plasma detachment.

Imploding z-pinch shells with total currents that are proportional to some power of time are investigated. Time-space separable self-similar solutions with cylindrical symmetry are explicitly obtained. The problem is treated asymptotically in high thermal conductivity within the model of magnetized resistive plasmas, while the ionization and radiation processes are ignored.

A dusty plasma consisting of cold and hot electrons, cold ions, and charge fluctuating isolated cold dust has been considered. It has been shown by a normal mode analysis that in such a dusty plasma there exists a new type of electrostatic perturbation mode due to the charge fluctuation of the isolated dust. The basic features of this new electrostatic perturbation mode, which are different from those of the electron-acoustic waves, have also been analytically identified. The implications of these results in both the space and laboratory dusty plasma conditions are briefly discussed.

In a suitable experimental device, laboratory plasma is produced with conditions and parameters analogous to magnetospheric plasma; we light a rare plasma in a semi-machine using rf-frequency discharge. Three ranges of low-frequency instabilities appear, one of which is identified as drift, caused by electron–neutral collisions. A full theoretical elaboration adapted to production conditions and geometrical symmetry is carried out; one solution of the dispersion relation is sufficient justification for the existence of the instability. The mathematical analysis also has the ambition to give interpretation for other low-frequency waves. Here we make a sound identification of the instability type as drift resistive due to electron–neutral collisions by an investigation of the growth rate. An agreement between experimental results and the theoretical model is obtained. As in the magnetosphere, an external magnetic field restrains the plasma.

A system of equations for modulational interaction of the electromagnetic branch of drift waves with magnetic cells is constructed. The solution of these equations describes formation of a set of magnetic cells with oppositely directed magnetic fields at their boundaries.

We consider an adiabatic dusty plasma containing adiabatic inertialess electrons, adiabatic ions, and adiabatic negatively charged dust. The basic features of the dust–ion-acoustic (DIA) as well as the dust-acoustic (DA) solitary waves (SWs) in such an adiabatic dusty plasma are investigated using the reductive perturbation method, which is valid for small amplitude SWs, and by the pseudo-potential approach which is valid for arbitrary amplitude SWs. The combined effects of the adiabaticity of electrons/ions and negatively charged static/mobile dust on the basic features (polarity, speed, amplitude and width) of small as well as arbitrary amplitude DIA and DA SWs are examined explicitly. It is found that the combined effects of the adiabaticity of electrons/ions and negatively charged static/mobile dust significantly modify the basic features (polarity, speed, amplitude and width) of the DIA and DA SWs. The implications of our results in space and laboratory dusty plasmas are discussed briefly.