A previous analysis of anomalous width variation for a single-ion rarefactive solitary wave [S. S. Ghosh and A. N. Sekar Iyengar, Phys. Plasmas, 4, 3204 (1997)] has been extended to a multi-ion species, and shows that the corresponding width–amplitude characteristics depend crucially on the respective ion concentrations; for example, with increasing light-ion concentration, an ‘increasing- width’ rarefactive solitary wave transforms to a ‘decreasing-width’ one for a constant Mach number exhibiting an overall U-shaped variation profile. The influence of the second ion species generally decreases with increasing amplitude, being maximum for the single to multi-ion transition. However, in the neighbourhood of double-layer-like solutions, the influence again becomes prominent, which may be associated with the corresponding energy–amplitude relations for both the ions.

This note investigates an ion-dust streaming instability with frequency ω less than the dust collision frequency νd, in an unmagnetized collisional dusty plasma. Under certain conditions, a resistive instability can be excited by an ion drift on the order of the ion thermal speed, even when the dust acoustic wave is heavily damped. The effect of weak collisions on the usual dust acoustic instability in the regime ω > νd is also considered. Applications to experimental observations of low-frequency fluctuations in laboratory d.c. glow discharge dusty plasmas are discussed.

A theoretical analysis of spherical probes in plasmas is presented. It is assumed that the probe is at floating potential, that ion motion with respect to the probe is radial and that the electrons are Maxwellian. The analysis shows that as probe radius divided by Debye length tends to zero, the ratio of floating potential to electron temperature also goes to zero.

We consider a model of viscoresistive incompressible magnetohydrodynamics in a periodic cylinder, with boundary conditions meant to idealize in a tractable way those of a laboratory plasma. The resistivity is described by a tensor presenting a field-dependent anisotropic part suggested by kinetic theory, controlled by a certain anisotropy parameter. An explicit analytical description of the corresponding axisymmetric zero-flow equilibria is given, and it is shown how tokamak-like or paramagnetic-pinch-like field profiles are obtained as the anisotropy parameter is changed. The study of the stability properties of such equilibria is deferred to a later paper.

The one-dimensional oblique propagation of magnetohydrodynamic waves with arbitrary amplitudes in a Hall plasma with isotropic pressure is studied under assumption that the plasma β is large. It is shown that the wave evolution is described by the derivative nonlinear Schrödinger equation (DNLS).

The distribution of plasma and electric fields close to the far side of the Moon are discussed. The existence of a strong double layer behind the Moon is predicted and its parameters are investigated. Electric currents associated with this double layer and finite conductivity inside the Moon are estimated. The fluxes of suprathermal electrons behind the Moon in different energy ranges are calculated and compared with the experimental data. It is shown that the theoretical results are in qualitative agreement with the data obtained by Lunar Prospector and the Apollo 15 subsatellite.