We examine the charging of dielectric dust grains embedded in a plasma. Our work is a continuation and refinement of our previous research into grain charging problems. In 1993, we discussed preliminary simulation results regarding the charging and intergrain forces between two dielectric dust particles [J. W. Manweiler et al., Adv. Space Res. 13, 10175 (1993)]. Then, in 1996, we discussed preliminary results with respect to dust grain charging within asymmetric plasma conditions and how these affect grain–grain collisional cross-sections [J. W. Manweiler et al., In: The Physics of Dusty Plasmas (ed. P. K. Shukla et al.), p. 22. World Scientific, Singapore (1996)]. This work was extended to evaluate how asymmetric charging affects coagulation rates for dielectric dust grains [J. W. Manweiler et al., In: Physics of Dusty Plasmas, 7th Workshop (ed. M. Horanyi et al.), p. 12. AIP Conf. Proc. 446 (1998)]. Here we report on the results of a significant refinement to our work to study the behaviour of a dielectric dust grain in a plasma with a bulk flow. Since charge transport is inhibited on our dielectric grains, we can examine how asymmetric plasma distributions affect the symmetry of the charge distributions that develop on the surfaces of the grains. A dielectric dust grain in a flowing plasma develops a negative total charge and a dipole moment in its charge distribution that points upstream. We also use this model to study how the presence of a nearby dust grain affects the development of a grain's charge distribution. We demonstrate that a smaller grain–grain separation results in a reduced net charge on each grain. For grains in a flowing plasma, dipole moments are unaffected by close approach except when one grain is directly in the ‘wake’ of the other grain. The studies here show that monopole and dipole electrostatic forces are present when dust is bathed in flowing plasma. Recent infrared studies suggest that a large fraction of young stars have dusty envelopes [G. Schilling, Science286, 66 (1999)]. In the formation of accretion discs around young stars, dust–plasma interactions are probably important. Full details on the calculations of the results discussed in this paper are summarized from a more complete treatment of the subject by Manweiler [PhD Dissertation, University of Kansas (1997)].

Relaxation phenomena in two-dimensional (2D) plasma crystals have been investigated, including both the self-consistent electric charge of dust particles and the electron and ion velocity distribution functions, by means of a modified 2D particle-in-cell (PIC) method. The results obtained show that the mutual interaction of dust particles in such crystals leads to special properties of the background electrons and ions due to their selective collection by dust particles during the relaxation. These electrons and ions can behave as non-ideal components of dusty plasmas in plasma crystals even in cases where their numbers in the Debye cube are large. This effect is caused by their intensive charge exchange with dust particles, which provides dusty plasmas with the status of open statistical systems. The selective collection of electrons and ions by dust particles also causes their deviation from the initial equilibrium as well as the non-equilibrium evolution of the self-consistent electric charge of the dust particles. Relaxation phenomena in plasma crystals have to be taken into account in all cases of strong changes of plasma parameters, for example due to strong oscillations and waves in these crystals.

Properties of global drift waves in a cylindrical weakly ionized magnetized plasma are studied analytically, and are compared with experimental observations.

The structure of a collisionless scrape-off-layer (SOL) plasma in tokamak reactors is studied in order to define the electron distribution function and the corresponding sheath potential between the divertor plate and the edge plasma. The collisionless model is shown to be valid during the thermal phase of plasma disruption, as well as during the newly desired low-recycling normal phase of operation with low-density, high-temperature, edge plasma conditions. An analytical solution is developed by solving the Fokker–Planck equation for electron distribution and balance in the SOL. The solution is in good agreement with numerical studies using Monte Carlo methods. The analytical solutions provide insight into the role of different physical and geometrical processes in a collisionless SOL during disruptions and during the enhanced phase of normal operation over a wide range of parameters.

The energy of a Landau-damped electrostatic wave is a long-standing problem. Calculations based on a spatially infinite wave are deficient. In this paper, a wave packet is analysed. The energy density depends on second-order initial conditions that are independent of the first-order wave. Pictures of energy and momentum transfer to resonant electrons are presented. On physical grounds, suitable second-order initial conditions are proposed. The resulting wave energy agrees with fluid theory. The ratio between energy and momentum is not the phase velocity up, as predicted by fluid theory, but ½up, in agreement with Landau-damping physics.

Effects of dust grain charge fluctuation, obliqueness and external magnetic field on a finite-amplitude dust acoustic solitary potential in a magnetized dusty plasma, consisting of electrons, ions and charge-fluctuating dust grains, are investigated using the reductive perturbation method. It is shown that such a magnetized dusty plasma system may support a dust acoustic solitary potential on a very slow time scale involving the motion of dust grains, whose charge is self- consistently determined by local electron and ion currents. The effects of dust grain charge fluctuation, external magnetic field and obliqueness are found to modify the properties of this dust acoustic solitary potential significantly. The implications of these results for some space and astrophysical dusty plasma systems, especially planetary ring systems and cometary tails, are briefly mentioned.

Transition radiation from the zone of injection of a modulated electron beam spiralling into a magnetoplasma has been identified as whistler waves propagating quasiparallel to the external magnetic field. The characteristics of the radiation are similar to the emission by localized sources, such as loop antennas and electric dipoles: resonance-cone structures at low plasma densities and energy flow along the external magnetic field at higher densities, with a diverging radiation pattern and with whistler phase velocities inversely proportional to the plasma frequency. These studies should contribute to a wider understanding of the physical processes connected with the injection of charges in a magnetoplasma – either from a gun on board a spacecraft or in a plasma chamber – and thus allow the determination of appropriate radiator characteristics in order to control, to some extent, plasma perturbations and wave emission in the region of the injector.