Three-component Plasma Research Articles

Plasma boundary layer in the presence of fast primary electrons

The fluid equations are solved for a three-component plasma in contact with a plane object whose surface is negatively biased or electrically floating. The plasma is assumed to consist of cold ions, fast monoenergetic primary electrons with isotropic velocities, and secondary electrons with a Maxwellian distribution. The rate of ionization is assumed to be proportional to the density of the primary electrons. For a certain range of plasma parameters multiple double layers are formed whose positions are quasiperiodic.

Scattering of electromagnetic waves by electron acoustic waves

It is shown that a large amplitude electromagnetic wave can parametrically excite low-frequency electrostatic modified electron acoustic waves which are unique to three-component plasmas ions, hot electrons and a group of cold electrons. The growth rates and thresholds of the decay instabilities are obtained. Application of our results in the auroral region of the ionosphere is illustrated.

Vortices in three-component plasmas.

Vortex structures in a hot plasma with cold impurity ions are investigated. It is shown that a new scalar nonlinearity resembling the well-known temperature gradient nonlinearity can appear.

Nonlinear propagation of Alfv�n waves in cometary plasmas

Large-amplitude Alfven waves propagating along the guide magnetic field in a three-component plasma are shown to be spatially localized due to their nonlinear interaction with nonresonant electrostatic density fluctuations. A new class of subsonic Alfven soliton solutions are found to exist in the three-component plasma. The Alfven solitons can be relevant in explaining the properties of hydromagnetic turbulence near the comets.

Kinetic theory of the thermal conductivity of a strongly coupled semiclassical hydrogen plasma.

A kinetic theory is presented for the thermal conductivity of a strongly coupled, fully ionized hydrogen plasma of typical temperature and density 10T104 eV, 1020n1027 cm-3. This theory gives results in good agreement with molecular dynamics and recovers weak-coupling-theory values at high temperature. The theory has then been generalized to a three-component hydrogen plasma made up of protons and electrons of spin up and spin down. It is found that the ionic part of the thermal conductivity cannot be neglected in the high-temperature high-density domain of the parameters. © 1986 The American Physical Society.

Ambipolar diffusion coefficients for discharges in attaching gases

A general expression is given for the ambipolar diffusion coefficients in a gas discharge plasma containing an arbitrary mixture of electrons and positive and negative ions. Specific examples of coefficients for three-component active discharges and afterglows (electrons, one type of singly charged negative ion, one type of singly charged positive ion) are presented. The general expression is also used to clarify the limitations associated with the coefficients for a three-component plasma published by Thompson (1959). The limitations are significant.

Experiments on ion-acoustic rarefactive solitons in a multi-component plasma with negative ions

Ion-acoustic solitons in a three-component plasma which consists of electrons and positive and negative ions have been investigated experimentally. When the concentration of negative ions is smaller than a certain value, positive or compressive solitons are observed. At the critical concentration, a broad pulse of small but finite amplitude propagates without changing its shape. When the concentration is larger than this value, negative or rarefactive solitons are excited. The velocity and the width of these solitons are measured and compared with predictions of the Korteweg-de Vries equation which takes the negative ions and the ion temperature into consideration. Head-on and overtaking collisions of the rarefactive solitons have been observed to show that the solitons are not affected by these collisions.

Temperature effects on low-frequency electric microfields in multicomponent plasmas.

A generalization of the Baranger-Mozer formalism is presented for a low-frequency thermal electric-microfield distribution. Correlation, proportion, temperature, and charge effects are included in this model for a three-component plasma (one electronic and two ionic). Results are presented for various ion mixtures in a range of temperature ratios encountered in dense and hot plasmas of inertial-confinement fusion produced by laser.

Instability of ionization equilibrium of a weakly ionized three-component plasma

The general stability conditions of a three-component plasma lead, in addition to the usual critical phenomena, to the appearance of a chemical instability, connected with the multiple solution of the law of mass action. As a result of a first-order transition the system will separate into two phases with different degrees of ionization. As the fraction of highly ionized phase increases, the conductivity of the system becomes metallic. Such a phenomenon can explain the metal-dielectric transition and its connection with such critical phenomena in different systems as weak electrolytes, molten salts, metal-ammonia solutions, and solid-state plasmas.

Diffusion and heat flow equations with allowance for large temperature differences between interacting species

For application to planetary ionospheres we have derived diffusion and heat flow equations for a fully ionized three‐component plasma and for a partially ionized three‐component plasma using a formulation that is valid for arbitrarily large temperature differences between the interacting species. These equations can be applied to ionospheric situations where steady state, collision‐dominated conditions prevail and where the species drift velocities are much less than the species thermal speeds (low Mach numbers). The application of the diffusion and heat flow equations to the F region and topside terrestrial ionosphere indicates that the various transport coefficients can exhibit significant variation with the different species temperature ratios.

Theory of cooled electric probes in a dense plasma. Influence of thermal diffusion

The problem of an electric probe in the shape of a sphere in a weakly ionized three-component plasma at rest is studied. It is assumed that the probe diameter is appreciably larger than the mean free path of the charged particles and that the temperature of the probe surface differs from the temperature of the undisturbed plasma. The contribution of thermal-diffusion mass transport is taken into account in the expressions for the densities of the electric currents of the components. A new numerical method is developed to obtain a solution of the problem in a wide range of the determining parameters. The current-voltage characteristics are constructed. The influence of the probe temperature, the transport coefficients, and other parameters on the current-voltage characteristics is analyzed.

Temperature effects in non-symmetric three-component counter-streaming electron plasmas: theory and computer simulation experiments

Temperature effects on the electrostatic instability of non-symmetric electron plasma systems consisting of two warm counter-streaming beams and of warm background particles are investigated linearly (analytically and numerically) and nonlinearly (by computer simulation experiments) for the case of Heaviside and moderately warm Maxwellian particle distribution functions. The non-symmetry is due to unequal temperatures, streaming velocities and particle densities in the beams. Other variable parameters investigated are the relative thermal velocities of the beams and background as well as the relative background particle concentration. When the beam temperatures are unequal, unstable waves with Re ω > 0 and propagating in the direction of the beam with lower temperature occur; this is in contrast to the equal temperature symmetric two-stream case, in which the unstable waves have Re ω = 0 (standing waves) and the temperature effect is only to decrease the growth rate. When three warm components are present in the system, the following results hold: (i) the beam temperatures have the effect of decreasing the importance of the unstable standing waves with Re ω > 0 (and growth rate yB) relative to the waves with Re w = 0 (growth rate yA) which occur in cold three-component symmetric systems; in addition to this, both γA, max and γB, max decrease with increasing temperature; (ii) the background temperature has the general effect of reducing the absolute maximum growth rate. For relative background temperatures above a certain critical value, a separation (in k and ω spaces) of regions B and A occurs; γA, max increases and γB, max decreases with increasing relative background temperature.

Three component non-symmetric counter-streaming instabilities: longitudinal electron plasma modes

The counter-streaming instabilities arising in three-component electron plasmas are investigated analytically and numerically in the general non-symmetric case, i.e. whenHere n1n2and narepresent the electron particle density in the first and second beams and in the background (ambient) stationary plasma, respectively; U1and U2represent the streaming velocities of the two counter-streaming electron beams. No magnetic or temperature effects are considered; consequently the three components interact only through the electric collective fields and only longitudinal modes are present. The positive ions here represent a stationary neutralizing background. Combined analytical and numerical solutions of the dispersion equation indicate that the basic properties of the unstable plasma modes may change significantly, depending on the values of the dimensionless parameters e, a and g. Thus, the standing wave spectrum (Re ω = 0) which occurs in the symmetric case (ε = a = 1) without background (gr = 0) may be replaced by a mixed travellingstanding wave spectrum having a rather complex structure; the maximum growth rate could be also strongly affected. The transformation of the instability from ‘absolute’ into mixed ‘convective and absolute’ may have significant physical implications, especially for finite size plasma systems or finite length unstable interaction regions. The results are relevant for laboratory and (especially) astrophysical situations in which counter-streaming electron beams having unequal streaming velocities (and particle densities) penetrate plasma regions with significant relative particle concentration.

Jovian sodium plasma

The nature of the sodium plasma created by ionization of the sodium emitted into the environment of Jupiter by Io is discussed. It is shown that the ions form a three-component plasma: cold, thermal, and energetic. Observational evidence for the effect of the plasma on the neutral sodium cloud is presented. The energetic component is predicted to generate ion cyclotron turbulence near the sodium gyrofrequency.

Motion of a nonequilibrium nonisothermal plasma in an electro-magnetic field

In calculating the flow of gases accompanied by large temperature changes it is often necessary to consider chemical reactions occuring in the flow. Until recently, beacuse of the complexity of an adequately strict description of chemical processes, studies have been limited to relatively simple cases, where the kinetics were described approximately [1–4] or more or less simple gasdynamic flows were considered [5–9]. In particular, in a magnetohydrodynamic accelerator, until the present the dynamics of a plasma, components with consideration of kinetic processes have remained practically unstudied, while information about these processes is highly necessary for a proper understanding of the functioning of such devices. In the literature there are a number of studies which perform numerical integration of the equations of plasma motion in accelerations with coaxial geometry. In these studies the plasma was assumed to be completely ionized, and the dependence σ (T) was approximated by some function. References to the literature and an overview of results on this question are presented in [10]. This present study will present the results of numerical integration of the equations describing the unidimensional flow of a three-component two-temperature plasma in a constant electromagnetic field with consideration of ionization and recombination reactions and compare the computed results with experimental data.

Influence of contaminants on the CO<inf>2</inf>electric-discharge laser

In CO 2 -N 2 -He electric-discharge lasers, small concentrations of impurities may be present in the original gases, or new species may be generated by the discharge. In order to determine the effects of such impurities, controlled amounts of possible contaminants were introduced into the amplifier of a CO 2 probe-amplifier system. Small-signal gain was reduced in all cases when CO, O 2 , NO, N 2 O, or NO 2 molecules were added. It was found that less than 0.1 percent of NO 2 or N 2 O markedly reduces the laser gain and alters the discharge impedance. A discharge model which describes a three-component positive-column plasma (electrons, positive ions, and negative ions) yields results consistent with the observations. The influence of attachment and detachment rates on molecular gas discharge characteristics and stability are studied.

Some processes in the magnetosphere

This paper is a continuation of the review (Shabansky, 1968), which is quoted here as I. This paper considers the problems related to the processes of the interaction of charged particles with the geomagnetic field, and also contains the original results obtained by the author (1, 2.1; 2.2; 2.3.4; 2.4; 3.1; 3.2; 3.3; 3.4.3). The problems under discussion in the Sections 1; 2.1; 2.2 were partly dealt with in the end of paper I. However, the equations of motion for the two-and three-component plasma shortly represented in 1.1, 1.2, take into account the inertial terms in distinction to paper I. The ionospheric current induction (1.4), the transition layer (2.1) and the magnetotail rotation (2.2) are considered in more detail than in I.

Transport coefficients for a partially ionized two-temperature plasma with ions and neutral particles having different masses

The viscosity, heat-conduction, and diffusion coefficients are calculated for a two-temperature three-component plasma composed of ions, neutral particles and electrons when the masses of the ions mi and neutral particles ma are different. Similar transport coefficients for mi=ma were calculated in [1–3]. The numerical values obtained for the transport coefficients are compared with the values calculated from the formulas of [1–3]. Numerical calculations are carried out for helium with a cesium additive (mi>ma) and for krypton with a lithium additive (mi<ma).

Instabilities Due to Interaction between a Slow Electron Beam and a Plasma

A mercury plasma is perturbed experimentally by a slow electron beam whose velocity is of the order of a thermal velocity of medium electrons. A special but a simple gun is used to drive the slow electron beam into a plasma region. The beam is therefore considered to be of the drifted Maxwellian distribution. Instabilities are classified into the two types; one of them is a wave of beam-electron coupling and the other is a wave of beam-ion coupling. Unstable regions are shown as a function of the frequency and the electron beam velocity, and explained on the basis of the theory of drift instability in three-component plasma system.

Production and Study of an Alkali Plasma with Negative Ions

The method of contact ionization is used to produce a three-component plasma (Cs+, Cl−, e−) in the Q-device BARBARA using a beam of Cesium chloride. The end-plate temperature controls the concentration of Cl−, which can be varied in a wide range. The density of negative ions is obtained from the difference between the positive ion density given by a Langmuir probe and the electron density given by a microwave resonator. A high concentration of negative ions is achieved.