Parts I and II of this paper present a comprehensive picture of longitudinal wave propagation in a warm homogeneous magnetoplasma. Part I discusses computed dispersion characteristics for propagation perpendicular to the static magnetic field. For a ring electron velocity distribution it is found that mode coupling and absolute instability can occur. Similar effects are predicted for a spherical shell distribution. The Maxwellian distribution gives rise to stable propagation of undamped waves, and attenuating standing waves. A mixture of ring and Maxwellian distributions can give absolute instability with stronger growth and lower instability thresholds than for the ring distribution alone. Propagation oblique to the static magnetic field will be dealt with in Part II.

Plasma waves in a bounded anisotropic plasma: Influence of the electron density inhomogeneity

It has been predicted theoretically that cyclotron harmonic waves should propagate in warm plasma confined by a magnetic field, and show cutoff and reso nance behavior associated with ha rmon ics of the cyclotron frequency and the upper hybrid resonance frequency. In thi s paper, a s implifi ed analy· sis based on the quas i·static approximation is presented and used to establi sh th e relevant di s pe rsion relations. Computer so lutions of th ese are presented s howing th e influ e nce of the magn e ti c field a nd discharge paramete rs on the propagation. A numbe r of rece nt ex pe rime ntal results ca n be ex pl ain ed in terms of this type of wave motion and se rve to establi s h its validity. This work is disc ussed bri efly. The paper disc usses so me of the implications of this mode in laboratory and ionos phe ri c plasma physics.

The plasma resonance probe was first studied by Takayama and his co-workers in 1960. Since that time several attempts have been made to determine precisely the experimental and theoretical behavior of the resonance. This paper reviews the various contributions made so far, and develops further the explanation advanced in 1963 by Harp. Detailed experiments have been carried out to confirm the predictions: (i) that the resonance frequency lies below the local electron plasma frequency, (ii) that it is dependent on probe potential and probe size and, (iii) that the resonance should be highly damped when probe dimensions are smaller than a few electronic Debye lengths. If the resonance probe is to be of great practical importance, a simplified theoretical model describing its behavior is desirable. The theory of such a model is presented and compared to experimental results. The paper concludes with a discussion of improved methods of applying the resonance probe, and suggests a ringing technique which provides electron density measurements in laboratory discharges in times of the order of a few cycles at the electron plasma frequency.

This paper describes the space-charge double-layer that forms between two plasmas with different densities and thermal energies. Three progressively more realistic models are treated by fluid theory, taking into account four species of particles: electrons and ions reflected by the double-layer, and electrons and ions transmitted through it. First, the two plasmas are assumed to be cold, and the self-consistent potential, electric field and space-charge distributions within the double-layer are determined. Second, the effects of thermal velocities are taken into account for the reflected particles, and the modifications to the cold plasma solutions are established. Third, the further modifications due to thermal velocities of the transmitted particles are examined. The applicability of a one-dimensional fluid description, rather than plasma kinetic theory, is discussed. One valuable product of this description is the potential difference across the double- layer in terms of the parameters of the two plasmas which it separates. A useful length parameter is defined characterizing the distance over which most of this potential is dropped. Comparisons are then made between theoretical predictions, and double-layer potentials and lengths deduced from laboratory and space plasma experiments.