The equivalent charge of photons in dense unmagnetized and magnetized Fermi plasmas is determined through the plasma physics method. This charge is associated with the polarization of the medium caused by the ponderomotive force of the electromagnetic waves. Relations for the coupling between the electron plasma density perturbation and the radiation fields are derived for unmagnetized and magnetized plasmas, taking into account the quantum force associated with the quantum Bohm potential in dense Fermi plasmas. The effective photon charge is then determined. The effects of the ion motion are also included in the investigation.

A diagnostic neutral beam (DNB) is applied to measure the plasma ion temperature and rotation speed in the HT-7 tokamak. Also, a heating neutral beam (HNB) is suggested as an effective method of heating a plasma for the EAST tokamak. As a necessary step to evaluate the required beam power in both applications, the attenuation of the injected neutral beam has been numerically calculated and analyzed considering the effect of various plasma parameters, such as electron temperature, electron density, impurity concentration, and so on. Three basic atomic processes are considered here. It is shown that at the same electron density neutral beam particles can penetrate deeper at higher injection energies and a DNB with the same full energy can attenuate faster at higher electron densities. The impurity effect on the attenuation of a DNB is discussed, and the attenuation of a HNB on the EAST tokamak is also considered.

The nonlinear dynamics of magnetic electron drift mode turbulence are outlined and the generation of large-scale magnetic structures in a non-uniform magnetized plasma by turbulent Reynolds stress is demonstrated. The loop-back of large-scale flows on the microturbulence is elucidated and the modulation of the electron drift mode turbulence spectrum in a medium with slowly varying parameters is presented. The wave kinetic equation in the presence of large-scale flows is derived and it can be seen that the small-scale turbulence and the large-scale structures form a self-regulating system. Finally, it is shown by the use of quasilinear theory that the shearing of microturbulence by the flows can be described by a diffusion equation in k-space and the corresponding diffusion coefficients are calculated.

By calculating the dielectric permittivity of a magnetoactive plasma discharge in the presence of an external electric field, low-frequency instabilities resulting from the dependency of the electron-neutral collision frequency, electron-ion recombination coefficient and ionization frequency on the electron temperature are investigated. Furthermore, it is shown that some of these instabilities depend on the sign change of the derivative of the kinetic coefficients with respect to the electron temperature. Finally, it is shown how frequency spectra and the development of instabilities are changed by increasing the strength of the external magnetic field.

By means of kinetic fluctuation theory, the relaxation process between the electron and ion temperatures in a magnetized homogeneous plasma is considered. The cases when the external upper-hybrid pump wave excites modified convective cells and ion-acoustic waves are analysed. The inverse relaxation time in the regime where the turbulent fluctuations are developed is calculated for these cases and its dependence on the pump wave and plasma parameters is deduced.

We present results from a particle–fluid simulation of auroral electrons and discuss the distribution of parallel electric fields along auroral field lines and the processes occurring during the build up of these electric fields. Neglecting field-aligned ion dynamics, the main potential drop has a width of about 5000, km and is centered at an altitude of roughly 5000, km. We find that the gradient in the potential becomes steeper and the build up of the potential drop becomes faster if the temperature of the magnetospheric electrons is lower.

In this communication the interaction between two Gaussian electromagnetic beams in an ionic collision dominated plasma has been investigated, when the axes of the two beams are initially (z = 0) parallel along the z-axis in the xz plane; the beams are initially propagating in the z-direction. Taking into account the loss of electron energy by collisions and by thermal conduction, the energy balance equation for electrons has been solved to obtain the space dependence of the electron temperature and the dielectric function has been expressed as a function of the electron temperature; this expression for the dielectric function has been substituted in the wave equation and a solution of the resulting nonlinear equation obtained in the paraxial approximation. Second-order coupled ordinary differential equations have been obtained for the distance between the centers of the beams and the beam widths in the x- and y-directions as a function of the distance of propagation along the z-axis. The equations have been solved numerically for a range of parameters and a discussion of the results is presented for the case when the two beams have the same axial irradiance, frequency and width. From simple considerations it is seen that the beams attract each other when 2xo < wro and in this situation beams are close enough for the paraxial approximation to be valid.

Assuming a non-relativistic three species electron–positron–ion plasma, the counterstreaming instability is investigated for waves propagating parallel and perpendicular to a homogeneous background magnetic field. From the exact linear dispersion relations, it is shown analytically how the growth rates change with increasing baryon loading, revealing new characteristics that cannot be found either for an unmagnetized plasma involving three particle species or for a plasma with only two particle species.

The dispersion relation for a quantum pair plasma is derived, by using a wave kinetic description. A general form of the kinetic dispersion relation for electrostatic waves in a two-component quantum plasma is established. The particular case of an electron–positron pair plasma is considered in detail. Exact expressions for Landau damping are derived, and the quasi-classical limit is discussed.

We present a new efficient wave decay channel involving nonlinear interactions between a compressional Alfvén wave, a kinetic Alfvén wave, and a modified ion sound wave in a magnetized plasma. It is found that the wave coupling strength of the ideal magnetohydrodynamic (MHD) theory is much increased when the effects due to the Hall current are included in a Hall–MHD description of wave–wave interactions. In particular, with a compressional Alfvén pump wave well described by the ideal MHD theory, we find that the growth rate is very high when the decay products have wavelengths of the order of the ion thermal gyroradius or shorter, in which case they must be described by the Hall–MHD equations. The significance of our results to the heating of space and laboratory plasmas as well as for the Solar corona and interstellar media are highlighted.

The linear dispersion relation for compressional magnetoacoustic waves in a quantum magnetoplasma is derived, taking into account the quantum Bohm potential and the magnetization of electrons due to the electron-1/2 spin effect. It is found that the quantum forces produce the wave dispersion at quantum scales, which depend on the external magnetic field strength.

The acceleration of ions by multiple laser pulses and their spontaneously generated electric and magnetic fields is investigated by using an analytical model for the latter. The relativistic equations of motion of test charged particles are solved numerically. It is found that the self-generated axial electric field plays an important role in the acceleration, and the energy of heavy test ions can reach several gigaelectronvolts.

We study the stability of circularly polarized Alfvén waves (pump waves) in Hall plasmas. First we re-derive the dispersion equation governing the pump wave stability without making an ad hoc assumption about the dependences of perturbations on time and the spatial variable. Then we study the stability of pump waves with small non-dimensional amplitude a (a ≪ 1) analytically, restricting our analysis to b < 1, where b is the ratio of the sound and Alfvén speed. Our main results are the following. The stability properties of right-hand polarized waves are qualitatively the same as in ideal MHD. For any values of b and the dispersion parameter τ they are subject to decay instability that occurs for wave numbers from a band with width of order a. The instability increment is also of order a. The left-hand polarized waves can be subject, in general, to three different types of instabilities. The first type is the modulational instability. It only occurs when b is smaller than a limiting value that depends on τ. Only perturbations with wave numbers smaller than a limiting value of order a are unstable. The instability increment is proportional to a2. The second type is the decay instability. It has the same properties as in the case of right-hand polarized waves; however, it occurs only when b < 1 τ. The third type is the beat instability. It occurs for any values of b and τ, and only perturbations with the wave numbers from a narrow band with the width of order a2 are unstable. The increment of this instability is proportional to a2, except for τ close to τc when it is proportional to a, where τc is a function of b.