[en] Nonlinear interactions of tenuous electron beam, background, unmagnetized plasma, and self-consistently generated Langmuir and ion-sound waves are analyzed in the framework of plasma weak turbulence kinetic theory. Full numerical solutions of the complete weak turbulence equations are obtained for the first time, which show the familiar plateau formation in the electron beam distribution and concomitant quasi-saturation of primary Langmuir waves, followed by fully nonlinear processes which include three-wave decay and induced-scattering processes. A detailed analysis reveals that the scattering off ions is an important nonlinear process which leads to prominent backscattered and long-wavelength Langmuir wave components. However, it is found that the decay process is also important, and that the nonlinear development of weak Langmuir turbulence critically depends on the initial conditions. Special attention is paid to the electron-to-ion temperature ratio, T_e/T_i, and the initial perturbation level. It is found that higher values of T_e/T_i promote the generation of backscattered Langmuir wave component, and that a higher initial wave intensity suppresses the backscattered component while significantly enhancing the long-wavelength Langmuir wave component

[en] An explicit expression for the effective dielectric tensor is derived to be utilized in the dispersion relation for a magnetized plasma with weak magnetic field gradients perpendicular to the ambient magnetic field. The components of this tensor incorporate the relevant contributions due to the inhomogeneity and are shown to satisfy the required symmetry conditions. The case of perpendicularly propagating ordinary mode waves is presented as example, and it is shown that significant differences may appear between the absorption coefficient resulting from the present formulation and results from other approaches from the literature which do not exhibit correct symmetry, including the prediction of an inhomogeneity driven instability near the electron cyclotron frequency. (author). 14 refs, 2 figs

[en] The authors investigate amplification of the auroral kilometric radiation over the geomagnetic poles. The physical parameters needed for the calculation are obtained from a particular model that approximately reproduces the conditions in the auroral zone, taking into account density gradients perpendicular to the geomagnetic field and also the parallel magnetic field gradient. The components of the dielectric tensor are calculated in the locally homogeneous plasma approximation, and the dispersion relation is exactly solved with all harmonics and powers of the Larmor radius needed for the convergency of the solution. The authors also make a ray tracing study in the geometrical optics approximation, using the method of Poeverlein. The ray tracing study shows that the spatial scale of inhomogeneity, perpendicular to the magnetic field, is a very important factor in the amplification and that the distance to obtain a given amplification can be substantially reduced when the density gradient is increased

[en] The study of wave propagation and absorption inhomogeneous plasmas can be made by using a formulation in which the dielectric properties of the plasma are described by an effective dielectric tensor which incorporates inhomogeneity effects, inserted into a dispersion relation which is formally the same as that of an homogeneous plasma. We have recently utilized this formalism in the study of electron cyclotron absorption in inhomogeneous media, both in the case of homogeneous magnetic field and in the case of inhomogeneous magnetic field. In the present paper we resume the study of the case with inhomogeneous magnetic field, in order to introduce a generalized dispersion function useful for the case of a Maxwellian plasma, and discuss some of its properties. (author). 10 refs

[en] The present paper intends to contribute with arguments to the discussion, demonstrating the consistency between the concept of effective dielectric tensor, derived according to the BGI (Beskin, Gurevich and Istomin) prescription, and a general formalism for the geometric optics in nonuniform plasmas, derived from an eikonal approximation. (author). 13 refs

[en] Expressions for an effective dielectric tensor for weakly relativistic magnetoactive plasmas with magnetic field inhomogeneity in the perpendicular direction where obtained dielectric tensor ε^eff_ij satisfies the required symmetry conditions and describes correctly the energy exchange between wave and particles in a stationary, non-homogeneous plasma, when utilized in a dispersion relation which is formally equal to the homogeneous one. Some numerical examples for electron-cyclotron absorption are presented. (author)

[en] We consider a plasma with electrons and ions described by different combinations of different forms of Kappa distributions, and also by bi-Maxwellian distributions, for investigation of the ion firehose instability. The investigation considers Kappa distributions with small value of the kappa index, which enhance the differences between Kappa distributions and bi-Maxwellian distributions. The results obtained show that different forms of anisotropic Kappa distributions for the ions can have significantly different effect on the growth rates of the instability. The results obtained also show significant effect of the shape of the electron distribution, as well as effect of the anisotropy of electron temperatures, on the growth rates and on the unstable spectral range of the ion firehose instability.

[en] The dispersion relation for electromagnetic waves in a magnetized plasma with weakly inhomogeneous magnetic field is investigated within the framework of a WKB approximation. A dispersion function useful for the case of plasma particles described by a generalized loss-cone distribution is introduced, valid for waves propagating in weakly relativistic plasmas, for any direction relative to the ambient magnetic field and to the inhomogeneity. This dispersion function is in some particular cases related to other plasma dispersion functions well known from the study of homogeneous plasmas. An application is made for the case of ordinary mode waves propagating perpendicularly to the magnetic field in inhomogeneous loss-cone plasmas. copyright 1997 The American Physical Society

[en] We investigate the dispersion relation for a magnetized plasma with weak magnetic field gradients perpendicular to the ambient magnetic field. An explicit expression for the effective dielectric tensor is derived, incorporating the relevant contributions due to the inhomogeneity, which include corrections to all orders in the small parameter ε, where ε=[(1/B₀)(dB₀/dx)]. It is shown that this effective dielectric tensor satisfies the required symmetry conditions and is the tensor which should be utilized in the dispersion relation, in order to describe correctly wave-particle interactions in media with inhomogeneous magnetic field. The case of high frequency oscillations propagating perpendicularly to the magnetic field in a Maxwellian plasma is considered as an example and the effect of inhomogeneities in the magnetic field upon the absorption coefficient and the optical depth of ordinary mode waves is discussed. A region of negative absorption coefficient is predicted near the electron cyclotron frequency for sufficiently high inhomogeneity. Moreoever, it is shown that significant differences may exist between the absorption coefficient evaluated with the present formulation and results from other approaches found in the literature which do not exhibit correct symmetry properties

[en] Published in summary form only