Inhomogeneous Magnetized Plasma Research Articles

Propagation of Waves through Magnetoplasrna Slab Within a Parallel-Plate Guide

By applying the variational equation is established for handling wave reaction theory, a variational propagation in a parallel-plate guide within which a magnetized inhomogeneous lossy plasma slab is inserted. The equation is then solved by the finite-element method along with the frontal solution algorithm. With such an approach, the reflection coefficient and the field distribution in the slab are obtained. In this study, the factors which may influence the propagation characteristics of the guide are studied. These factors include the plasma electron density, the strength and the direction of the static magnetic field, the width and the thickness of the slab, and the electron collision Iosses. A special modal expansion solution is also incorporated to investigate an anomalous numerical instability associated with the present numerical algorithm.

DENSITY PROFILE STEEPENING DUE TO LASER RADIATION IN A MAGNETIZED INHOMOGENEOUS PLASMA

The effects of self-generated magnetic field on the density profile modification in laserplasma interactions are studied by calculating the field structure, assuming that plane electromagnetic waves propagate into an one-dimensional inhomogeneous magnetized plasma. The results obtained by computation are in agreement not only with the laser-target experiments using Nd-glass laser, but also with that using CO2 laser. In addition, calculations show naturally the density dip which has been observed in experiments.

The Field Structure and Absorption of Laser Radiation in a Magnetized Inhomogeneous Plasma

In this paper, the authors consider a more realistic case of linear density profile for laser-irradiated plasma, and obtain the field structure over the whole coronal region by directly solving the wave equation with numerical method. The dependence of the field structure on the wavelength of incident Laser light, the initial scale length of the density profile and the magnitude of the magnetic field is studied. In addition, the resonant absorption is also discussed for the above cases. The results are in good agreement with those obtained by computer simulations.

Field distributions of trapped electron Bernstein waves launched by a point source in an inhomogeneous magnetoplasma

In an inhomogeneous magnetized plasma, field distributions of trapped electrostatic cyclotron harmonic waves are investigated numerically when an external point source is located outside or inside the plasma. The trapped field amplitudes and wave patterns are obtained spatially in the inhomogeneous plasma.

Self-organization processes in continuous media

Abstract This review considers the dynamical behaviour of dissipative continuous media which can be described by nonlinear partial differential equations having more than two non-trivial conserved quantities in the absence of dissipation. Such a medium often exhibits a spectral condensation of a certain physical quantity to a specific wavenumber region resulting in the formation of an ordered structure, even when starting from an initially turbulent state or one driven by a stochastic field. Examples discussed here include two-dimensional incompressible fluids, two-and three-dimensional magnetohydrodynamic fluids, the atmospheres of rotating planets, the electrostatic potential in inhomogeneous magnetized plasmas, and the solition gas as described by the Korteweg-de Vries equation. The relationship between the onset of chaos and self-organization in a soliton system, as well as in some localized vortex solutions, is also discussed.

ON THE TWO DIMENSIONAL SOLITARY DRIFT WAVES IN THE INHOMOGENEOUS MAGNETIZED PLASMA

The paper presents a nonlinear MHD equation describing 2-D inhomogeneous magnetized plasma. Then a 2-D solitary vortex solution was given. Its structure is similar to the solution obtained in papers [2, 3], but it differs from the latter in several aspects. There is no restriction on the values of vortex speeds and the solitary waves can propagate in any direction in the plane with magnetic field B as its normal. The plasma is adhered to the vortex and moving along with it across B. This implies that the existence of solitary vortices is connected with anomalous transport of plasma.

Inverse resonance absorption in an inhomogeneous magnetized plasma

The linear mode conversion of a plasma wave to a light wave in a magnetized plasma has been examined theoretically and by computer simulation. This conversion is the inverse of resonance absorption exhibiting an identical dependence on magnetic field and density scale length with an optimum conversion efficiency of approximately 60%. Radiation from this source may contribute to the harmonic spectra observed from laser-irradiated plasmas.

Nonlinear generation of magnetostatic fluctuations by drift waves

It is shown that nonlinear-mode coupling of drift waves can generate magnetostatic fluctuations in an inhomogeneous magnetized plasma. The growth rate of the parametric instability is estimated for typical tokamak parameters.

Electron drift solitons in an inhomogeneous magnetized plasma

It is shown that electron drift solitons can exist in an inhomogeneous magnetized plasma. Two such types of solitons are discussed, one which is similar to the solitons described by the one-dimensional Korteweg-de Vries equation, and a second which is an analog of the two-dimensional Rossby solitons.

Raman Backscatter from an Inhomogeneous Magnetized Plasma

Raman backscatter of intense laser light from an inhomogeneous plasma in the presence of a self-generated magnetic field is studied by means of simulations with use of a 1\textonehalf{}-dimensional particle code. The magnetic field results in a significant blue shift in the frequency of the backscattered light. Emission levels show a dependence on magnetic field that is consistent with linear mode conversion of the scattered light wave.

Erratum: ‘‘Quasilinear theory of inhomogeneous magnetized plasmas’’ [Phys. Fluids 2 6, 468 (1983)

Erratum: ‘‘Quasilinear theory of inhomogeneous magnetized plasmas’’ [Phys. Fluids <b>2</b> <b>6</b>, 468 (1983)

Quasilinear theory of inhomogeneous magnetized plasmas

The quasilinear equations are derived for an inhomogeneous magnetized plasma without using the random phase approximation and the expansion in the ratio of the Larmor radius to the inhomogeneity scale. The equations take into account both resonant and nonresonant interactions, and possess the necessary conservation properties.

Spatial Investigations of Point-Radiated Fields above the Electron Cyclotron Frequency in an Inhomogeneous Magnetized Plasma

Spatial behaviors of mode-converted electron Bernstein waves at the upper hybrid layer in an inhomogeneous magnetized plasma are investigated experimentally and theoretically when the radiated source is located outside the upper hybrid layer. The theoretical spatial field patterns in two dimensions which include the mode-converted cyclotron harmonic wave radiated from a point source are found to be in near accord with the experimental results.

Spatial investigations of mode conversion between an electrostatic cyclotron harmonic wave and an electromagnetic ordinary wave

In an inhomogeneous magnetized plasma, mode conversions of an electrostatic cyclotron harmonic wave into an electromagnetic ordinary wave and vice versa are spatially investigated by a study of the ray trajectories and the wave fronts. Electrostatic cyclotron harmonic waves are found to be spatially trapped between the upper hybrid frequency layers.

Wave fronts of electromagnetic cyclotron harmonic waves

In an inhomogeneous high-density magnetized plasma, the spatial properties of the wave fronts and ray trajectories of electromagnetic ordinary and extraordinary cyclotron harmonic waves are investigated. Those waves which are radiated from a local source are found to have wave fronts which are almost parallel to the magnetic field. Also, the reflective properties of the electromagnetic cyclotron harmonic waves are confirmed.

Oblique Electron Thermal Waves in a Magnetized Plasma

Propagations of an oblique electron thermal mode under the electron plasma frequency without boundary effects are investigated experimentally and theoretically in a magnetized plasma. The phase, ray, and group velocity surfaces of the electron thermal mode are obtained in a polar coordinate. The experimental observation of the electron mode radiated from a point source is found to be in fair accord with the theoretical wave fronts which are obtained from the ray velocity surface. Wave fronts and ray trajectories of an oblique electron thermal mode radiated from a point source are numerically obtained in an inhomogeneous magnetized plasma with a use of an electrostatic kinetic theory. The spatial numerical results are indicated mainly below the electron plasma and cyclotron frequencies. Reflections of the mode in the plasma density lower than the electron plasma frequency are made clear numerically.

Parametrically induced low-frequency waves in weakly inhomogeneous magnetized plasmas

The linear dispersion relation governing the parametric interaction of a lower hybrid (or an electron plasma) pump wave with a weakly-inhomogeneous current carrying hot plasma confined by a helical magnetic field is derived and solved numerically. The stability boundaries are delineated over a wide range of the k-space. The frequency and growth rate of decay instabilities are calculated for plasma parameters relevant to lower hybrid plasma heating experiments. The parametric excitation of drift waves and ion cyclotron current instabilities is discussed. In the low-density plasma region low minimum thresholds and high growth rates are obtained for the pump decay into ion cyclotron and nonresonant quasimodes. The spatial amplification of hot ion Bernstein waves and nonresonant quasimodes dominate in the plasma core ( omega 0/ omega LH<2). The presented theoretical results are in qualitative agreement with current LH plasma heating experiments.

Nonlinear Magnetic Islands and Anomalous Electron Thermal Conductivity

It is found that nonlinear magnetic islands are formed, in an inhomogeneous magnetized plasma, in the presence of a longitudinal current. These magnetic islands may cause an enhanced electron thermal conductivity in a turbulent plasma state.

General Geometric Optics Formalism in Plasmas

This paper exploits a general approach to geometric optics in inhomogeneous plasmas based on the properties of the local dielectric tensor ?. We express ? in terms of its eigenvalues ?j and eigenvectors ?. Then to zeroth order in the geometric optics approximation the determinant D = ?1?2?3 vanishes and the elements ?j vanish separately in pairs or simultaneously. It is shown that this branching in the dispersion relation changes the formulation of the geometric optics equations. The ray tracing and the transport of the amplitude of the wave in both degenerate and nondegenerate cases is described. The general procedure for transition through a boundary between degenerate and nondegenerate regions, where the rays split into two parts each following a different branch of the dispersion relation is also presented in this paper. We demonstrate our general method in a case, where radiation from a vacuum region enters an inhomogeneous magnetized plasma layer.

Mode Coupling in the Solar Corona. VI. Direct Conversion of Langmuir Waves into o-mode Waves

Fundamental plasma radiation can result from direct coupling of Langmuir waves into o-mode waves in an inhomogeneous magnetized plasma. The coupling occurs for Langmuir waves propagating nearly along the direction of increasing plasma density, and the resulting o-mode waves propagate towards lower plasma densities. An analytic theory for the coupling (which is of z-mode waves into o-mode waves) is developed using approximate solutions of the Booker quartic equation. The results are shown to agree with the results of numerical calculations for the 'Ellis window' in 'the generation of the z trace in the terrestrial ionosphere. This 'direct conversion' of Langmuir waves into o-mode waves is an alternative mechanism for fundamental plasma emission, possibly replacing or supplementing the more familiar scattering from the charge clouds around thermal ions. Possible applications of 'direct conversion' to various solar radio bursts are explored, but for none is it found to be more favourable than alternative mechanisms.