Charge transfer and diffusion cross-sections of low-lying excited states are calculated using ab initio quantum-mechanical potential-energy curves. These data are used to calculate the reactive thermal conductivity λR of an atmospheric nitrogen plasma. Differences of up to 20 % are found between the present values of λR and the corresponding values obtained by increasing the cross-sections of excited states by a factor of 2. These differences propagate, to a minor extent (10 %), in the total thermal conductivity.

In this paper, we derive a kinetic equation and discuss its validity for a stationary turbulent plasma. We use, for this purpose, the Dupree— Weinstock model in the weak-coupling approximation, and take into account ballistic streams. Frictional effects appear, in addition to the velocity diffusion. The diffusion causes a resonance broadening, the friction causes a frequency shift. Our model is a generalization of the dressed test particle model, and leads to a kinetic equation formally similar to Balescu— Lenard' s. A comparison between our model and the Dupree ‘clump’ theory is developed. Physical quantities are conserved, the H theorem is satisfied; but the asymptotic solution is not necessarily a Maxwellian distribution function.

‘On effects of neutral gas friction and ion viscosity on the Rayleigh-Taylor instability of a stratified plasma in the presence of Hall currents’

By P. K. Bhatia,

J. Plasma Phys. vol. 11, 1974, pp. 1–10

Bhatia (1974) investigated the effects of neutral gas friction and ion viscosity on the dynamical stability of a composite plasma of variable density in the presence of the effects of Hall currents.

An attempt is made to trace the physical origin of the complex roots of the dispersion relation for a Maxwellian, non-relativistic, homogeneous, magnetized Vlasov plasma. For simplicity, the identification process is performed for the case of propagation perpendicular to the magnetic field. For a given real ω, there are infinitely many complex roots, in addition to a finite number of propagating solutions. The propagating waves correspond (in addition to the cold-plasma waves) to either the extraordinary Gross— Bernstein mode propagating just above the harmonics, or the pair of Dnestrovskij— Kostomarov modes (one ordinary and the other extraordinary) propagating just below the harmonics. The hot-plasma solutions asymptotically approach the harmonic frequencies as k‖→∞, and analytically continue across the harmonics as complex waves. These complex waves, originating in groups of three from each cyclotron harmonic, apparently remain distinct, giving rise to an infinity of complex roots for a given frequency (since there are an infinite number of cyclotron harmonics). Detailed analysis reveals that, for the ordinary and the extraordinary Dnestrovskij-Kostomarov modes, electric displacement and magnetic induction, respectively, are the dominant field components.

The exact surface-wave dispersion relation is expressed in terms of elementary functions for a plasma characterized by a ‘resonance’ velocity distribution function. An approximate form of the relation is derived for the case when the thermal velocity spread is much less than c. The pure surface wave obtained by dropping the term responsible for Landau damping is compared with that predicted on the basis of a fluid model of the plasma. The effect of Landau damping is then investigated, both by analytic approximations and by computation. Two branches of the solution to the dispersion relation are found; and it is shown that the surface wave suffers increasingly severe damping as the frequency grows beyond 1/ √ 2 times the plasma frequency. It is argued that qualitatively similar damping would be present were the plasma to have a Maxwellian equilibrium distribution function.

Index to Volume13, 1975

It is regretted that the following was omitted:

Landatj, R. W. New, almost electrostatic, anisotropy instability, 377