Spontaneous generation of an axial magnetic field is predicted when the usually neglected centripetal acceleration term is properly taken into account in the two-fluid equations of motion for a cylindrically symmetric imploding plasma. An order-of-magnitude calculation is presented to illustrate spontaneous generation of a reversed-field configuration in a plasma imploded by a metallic liner.

The spectra and the instability criteria for the two electromagnetic wave modes previously found to exist in weakly ionized plasmas placed in an external d.c. electric field are analysed here for neon plasma for a wide range of the parameter Eo/nn. The presence of electron-atom inelastic collisions is taken into account, assuming that the electron temperature is in the range where these collisions dominantly result in atomic excitations. The linearized kinetic equations are used in combination with a previously evaluated non-Maxwellian electron steady-state distribution function appropriate for the situation in which collisional excitations are significant. For any given ratio of electron drift to thermal velocity, the wavelengths and the angles of propagation at which the instabilities are predicted to set in are determined.

This paper deals with degenerate Fermi–Dirac plasmas in which transport is by quasi-particles that form a dilute gas described by the Boltzmann equation. The off-equilibrium part of the distribution function of each species is estimated by expanding it in terms of the fluid velocity of the species, relative to the plasma, and its relative heat flux vector. Expressions for the frictional forces acting between the species, consisting of a relaxation-model force and a thermal force, are obtained. These are used in a plasma dissipation formalism, yielding, for ternary partially ionized plasmas, a generalized Ohm law and an ambipolar diffusion law. The results are applied to neutron star matter, consisting of thermally ultra-relativistic electrons and non-relativistic protons and neutrons, with the mass density dominated by the neutrons. The dissipation formalism is used to obtain an expression for the magnetic force on this material.

A dispersion relation for electrostatic waves in a current-carrying, resistive, magnetized, two-ion plasma has been solved numerically for a range of parameter values. The behaviour of the resistive ion-ion hybrid instability is described and in addition a two-stream ion-ion hybrid instability is identified.

The problem of controlling the position and cross-sectional shape of plasmas is addressed for circumstances relevant to large tokamaks. A principle for, as well as a practical method of analysis of, this control problem is presented. The relevant elements of the tokamak system included in the analysis are the plasma, a resistive wall (vacuum chamber wall) surrounding the plasma, toroidally wound coils which also surround the plasma, as well as their associated external circuitry and a number of monitors of properties of the magnetic field in the vicinity of the plasma; the signals obtained from these monitors are used for control of power supplies which are part of the external circuits.

A start-up method for producing a plasma in the bi-cusp field configuration of a toroidal magnetic cusp (TORMAC) is described. The method uses the radial injection and trapping of a toroidal gun plasma. Measurements of an injected plasma with a velocity of 17 μsec–1 and 4·5 × 1018 particles is presented. The plasma was observed to be stopped and trapped in an equilibrium position. A well-defined outer boundary remained stationary for 20 μsec. Particle flux distribution emanating from the cusp field lines defined a sheath having a width of 1–1·5 ion gyroradii in the poloidial field. This translates to a narrow outer boundary and a broad inner boundary based on the gradient of the poloidial field at the two radial positions. Measurements of Thomson scattering and interferometry give a Te of 15eV, a 15μsec density decay time, and a 5μsec energy decay time. These results show that this injection and trapping method is successful, and thus a higher gun plasma energy combined with a flux conserving barrier may lead to higher temperatures for testing containment in TORMAC.

The first critical fast Mach number is rigorously defined to be the one at which the downstream flow speed in the shock frame equals the ordinary downstream sound speed. Above the first critical Mach number, resistivity alone is unable to provide all the dissipation needed for the required Rankine-Hugoniot shock jump. A survey of the dependence of the first critical Mach number upon upstream plasma parameters is needed to guide studies of the structure of collisionless shocks in space. We vary the upstream plasma beta, the upstream shock normal angle, and the ratio of specific heats for the plasma. The first critical Mach number depends sensitively upon upstream plasma parameters, and is between 1 and 2 for typical solar wind parameters, rather than the often quoted value of 2·7, which is valid for perpendicular shocks propagating into a cold plasma. We introduce the suggestion that the flux of superthermal and energetic ions upstream at quasi-parallel shocks might increase suddenly at the first critical Mach number. Our parametric survey indicates that this hypothesis might be most conveniently tested using interplanetary shocks.

A phase integral (WKBJ) theory of damped modes in a resistive cylindrical plasma column is developed. The theory predicts several phenomena observed previously in numerical studies: (i) the complex frequency ω has a point spectrum lying on a locus which is approximately independent of the resistivity, and which intersects the ideal continuum only at its end points (at angles of 45° and 30°); (ii) the qualitative features are independent of current profile and m–number, provided |k.B| is monotonic and strictly positive; and (iii) the two branches of the spectral locus joining the two end points of the ideal continuum correspond to precisely defined ‘internal’ and ‘wall’ modes, and bifurcate from a ‘global’ mode at a certain complex frequency which can be predicted from the topological features of the Stokes diagram in the complex radial position plane. In order to derive consistent connexion formulae for reflexions from the wall, the magnetic axis, and from turning points, we reduce the resistive hydromagnetic equations to a scalar wave equation, uniformly valid over the entire plasma to two orders in an expansion in the square root of the resistivity. Good numerical agreement is found between eigenvalues from the full equations, the reduced equation, and from the WKBJ method.

An original method for calculating and representing the excitation coefficients of longitudinal electron waves is applied to the case of a hot, collisionless, homogeneous and isotropie plasma with a bi-Maxwellian velocity distribution function. Using a Van Kampen treatment we introduce a ‘wave density’ distribution which is represented graphically. When hot electrons are added to a plasma of cool electrons the Landau mode is distorted and its damping increases with the hot/cold temperature ratio θ. The Landau mode separates into two modes for θ ≥ θ0 where θ0 increases as the hot/cold density ratio α decreases. We show that no wave seems to be able to propagate at frequencies below the plasma frequency. Using an abrupt cut-off in the hot electron distribution function, we recover the results for a Maxwellian plus water-bag distribution.

Two continued fraction expansions for the plasma dispersion function are given. The first is a very simple expansion for which error estimates can be obtained and which provides better approximations as the modulus of the argument increases. The second, while not so simple, provides whole range approximations.

The nonlinear propagation of a circularly polarized, electromagnetic wave in a collisional, infinite, magnetized plasma is considered. The presence of collisions leads to spatial variation in the amplitude of the wave field which gives rise to a time-independent ponderomotive force. The ponderomotive potential for a left (right) circularly polarized wave attains a maximum at the ion (electron) cyclotron frequency. In the vicinity of the cyclotron frequency it is shown to be always positive. A decrease in both the particle density and the real and imaginary parts of the complex wavenumber is shown to result from the effect of the ponderomotive force.