Search

A summary of earlier results partaining to the calculation of the Fokker-Planck coefficients in a plasma are given. The contribution due to electrostatic interaction is explicitly evaluated. Then the distribution of the stochastic magnetic field is considered. A technique is developed to calculate the distribution of the field due to particles revolving in the combined externally imposed and stochastic field. (Author)

The collective motion of a plasma due to the static magnetic interaction between the particles was studied with the aid of the Random Phase Approximation. A close analogy with plasma oscillations is demonstrated. An equation of motion is established. The motion may assume oscillatory or unstable character, depending on the unisotropy of the velocity-distribution. No collective motion is excited in thermal equilibrium. Then the effect of a more sophisticated model where both external magnetic field and the coupling of the two component species are taken into account, is considered. The stabilizing effect of the magnetic field, and new modes, such as magnetohydrodynamic waves, cyclotron waves, a peculiar two-component instability, are derived. Next, a general dispersion-relation is considered. The motion is decomposed into individual and collective contributions and selfconsistency requirement establishes the dispersion-relation. For large wave numbers the oscillatory motion suffers a Landau-damping, while in the case of increasing modes there is a maximum wave number that limits the spectrum of instabilities. Finally a beams treatment supplements the analysis. (Author)

Questions connected with the statistics of field quantities are considered. The model is a system of uncorrelated random sources: the field quantities being linear and instantaneous functions of the source coordinates. General properties of the C function, non-uniform particle density, the evaluation of the C function for binary field correlations are studied. Polynomial expansion in terms of the Fourier-component of the non-uniformity and the distance and inverse distance between the correlation points are given. (Author)

A perturbation analysis of the energy loss suffered by a test particle travelling through a plasma is considered. The action of the system on the particle is described as a combined result due to the polarization of the medium and to the correlated fluctuations of the electric microfield. The calculation is extended up to order e6. Higher order effects appear through binary, ternary etc. time correlations of the electric field and its derivatives related to a single point, to the points of a triangle, etc. of the unperturbed system. The possibility of a systematic extension to higher orders is indicated. (Author)

The polarization of the plasma particles in the neighborhood of a moving ion depends on the ion velocity. This affects the distribution of the stochastic field acting upon the ion. Correction to the Holtsmark distribution due to the complete test particle - field particle correlation including this dynamic effect is calculated up to the order e to the second power. The result is: (1) shift toward smaller fields, (2) anisotropy and (3) velocity dependence, which is not equal to the zero velocity effect even on the average. (Author)

Papers presented at seminar, 1963.