Electrical conductivity and conductive opacity of a relativistic electron gas
Electrical conductivity and conductive opacity for relativistic electron gas in presence of ions taking into account ion-ion interaction
Canuto, V.↗
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Perturbation theory of structure in classical liquid mixtures: Application to metallic systems near phase separation
The partial structure factors of classical simple liquid mixtures near phase separation are dicussed. The theory is developed for particles interacting through pair potentials, and is thus appropriate both to insulating fluids, and also to metallic systems if these may be described by an effective ion-ion pair interaction. The motivation arose from consideration of metallic liquid mixtures, in which resistive anomalies have been observed near phase separation. A mean field theory correction appropriate to 3 pair potential for the effects of correlated motions in the reference fluid is studied. The work is cast in terms of functions which are closely related to the direct correlation functions of Ornstein and Zernike. The results are qualitatively in accord with physical expectations. Quantitative agreement with experiment seems to turn on the selection of the hard core reference potential in terms of the metallic effective pair potential. It is suggested that the present effective pair potentials are perhaps not properly used to calculate the metallic structure factors at long wavelength.
Henderson, R. L.↗
The mobility and diffusion of ions in gases
Experimental and theoretical aspects of the mobility and diffusion of ions in gases are studied in detail. Some of the subjects discussed include ion-ion interaction, boundary condition and ion and electron behavior. Also discussed in separate chapters are the problems of the diffusion coefficients and the afterglow techniques. Finally, a special chapter studies the kinetic theory of diffusion and mobility, stressing the low-, medium- and high-field theory.
Mcdaniel, E. W.↗
Adhesion of a bimetallic interface
The Hohenberg-Kohn and Kohn-Sham formalisms are used to examine binding (binding energy as a function of separation) for combinations of the simple metals Al(111), Zn(0001), Mg(0001), and Na(110) in contact. Similar metal contacts between Al, Zn, Mg, and Na are examined self-consistently in an ab initio calculation using the Kohn-Sham formalism. Crystallinity is included using the Aschroft pseudopotential via first order perturbation theory for the electron-ion interaction; and the ion-ion interaction is included exactly via a lattice sum. Binding energy was determined both in the local-density approximation and including gradient corrections to the exchange and correlation energy. Binding was found in all cases. In dissimilar metal contacts, interfacial bonding was greater than that in the weaker material predicting the possibility of metallic transfer. The nonzero position of the energy minimum in like metal contacts is explained in terms of consistency between the Ashcroft pseudopotential and the bulk charge density. Good agreement with experimental surface energies is obtained in the self-consistent calculation when nonlocal terms are included.
Ferrante, J.↗
Microscale instabilities in stream interaction regions
The microstructure of solar wind stream interaction regions is considered theoretically with emphasis on the role of several electrostatic kinetic instabilities which may be important within the stream interface and the compression region. Inside of 1 AU, the interface is likely to be stable against the electrostatic streaming instabilities considered. Between 1 and 2 AU, the interface will excite the magnetized ion-ion instability. The compression region is also found to be unstable beyond 1 AU where the modified two-stream instability, beam-cyclotron instability, and ion-acoustic instability are important in determining the structure of the compressive pulses as they evolve into forward and reverse shocks. It is concluded that the modified two-stream instability and beam-cyclotron instability predominately play a role in heating the electrons to the threshold for the ion-acoustic instability. Various electrostatic plasma waves, ranging in frequency from the lower-hybrid to harmonics of the electron cyclotron frequency, would be produced by these instabilities. Their signature should also be seen by high time resolution measurements of the temperature of the various plasma species.
Eviatar, A.↗
Microscale instabilities in stream interaction regions
A theoretical investigation of the microstructure of solar wind stream interaction regions is presented. The role of several electrostatic kinetic instabilities is discussed which may be important within the stream interface and the compression region. Inside of 1 AU the interface is likely to be stable against the electrostatic streaming instabilities considered. Between 1 and 2 AU it is argued that the interface will excite the magnetized ion-ion instability. The compression region is also found to be unstable beyond 1 AU, where the modified two-stream instability, beam-cyclotron instability, and ion-acoustic instability will be important in determining the structure of the compressive pulses as they evolve into forward and reverse shocks. It is concluded that the modified two-stream instability and beam-cyclotron instability predominately play a role in heating the electrons to the threshold for the ion-acoustic instability.
Eviatar, A.↗
An analysis of the shocklike electrostatic noise observed during AMPTE solar wind ion releases
Electrostatic waves produced by the interaction of the ion cloud with the solar wind are analyzed in order to explain the shocklike noise detected by the Ion Release Module instruments during the Active Magnetospheric Particle Tracer Explorers solar wind ion releases. The results indicate that the shocklike noise can be generated by two instabilities, an ion-electron instability that occurs for waves propagating parallel to the solar wind velocity and an ion-ion instability that occurs for waves propagating at a large angle to the solar wind direction. Both instabilities give high growth rates for both the lithium and barium releases. The calculated results agree with the observed ones in all main features. In the earlier stage of the ion cloud expansion, both instabilities are likely to occur, while in the later stage the ion-ion instability is more likely to occur.
Ma, T. Z.↗
Transverse ion heating in multicomponent plasmas
A new mechanism is proposed for plasma modes which can occur only in a multicomponent plasma and not in pure electron-ion plasma. The addition of ions creates a new instability near the ion-ion hybrid mode whose frequency is adequate for the wave to interact with oxygen ions. To study heating of ions (such as ionospheric oxygen ions) in presence of auroral electrons, several numerical simulations were carried out using a one-dimensional electrostatic code in a magnetic field. It was found that in the presence of electrons drifting along auroral field lines into the ionosphere, the ion-ion hybrid mode can be driven unstable when the electron drift speed is too small to excite the lower hybrid instability. Since the ion-ion mode has a smaller frequency than that of the lower hybrid waves, it can couple to the heavy ions, resulting in a substantial heating of heavy ions; on the other hand, because of their frequencies, the lower hybrid waves can accelerate only light ion species.
Ashour-Abdalla, M.↗
Plasma instability in the presence of negative ions
Ion density fluctuations are studied in a diffusion-controlled argon plasma containing, as a dilutant, two electron-attaching species, carbon dioxide and sulfur hexafluoride. It is found that the system becomes increasingly unstable as the concentration of the electron-attaching species is increased. Nonlinear mode-mode couplings have been identified and the coupling coefficients for these interactions have been computed. Turbulent fluctuations are observed to have pronounced three-dimensionality with distinct axial and azimuthal behaviors. The power spectra of these fluctuations are composed of many discrete modes. The importance of changes in the total discharge pressure is dependent on the electron-attachment cross section of the dilutant species. From these results it is shown that the ionization instability is probably responsible for the observed phenomenon.
Johnson, J. A., III↗
Linear instabilities in multicomponent plasmas and their consequences for the auroral zone
Ion conics are commonly observed along auroral-zone field lines and involve all major terrestrial ion species, including H, He, and O. It is believed that low-frequency plasma waves, driven unstable by field-aligned currents, transversely heat the ion distributions via wave-particles interactions, creating the ion conics. Considered here are low-frequency oblique electrostatic instabilities found in a mixed plasma that includes an electron beam streaming through a background of electrons, H and O. The addition of O not only modifies the lower hybird frequency, but allows the existence of an ion-ion (Buchsbaum) hybrid mode with a frequency between the H and O gyrofrequencies. Because of its low frequency, the ion-ion hybrid instability can be effective in transversely heating heavy ions. When the electron beam drift speed is greater than 3 times the background electron thermal velocity and the electron gyrofrequency to plasma frequency ratio is less than 10, the lower hybrid instability dominates. However, for ratios greater than 20, which is a condition commonly found in the auroral-zone nightside region, the ion-ion instability has the largest growth rates; in these regions, heavy ion transverse heating can occur. When the ratio is between 10 and 20, the H to O density ratio determines which instability dominates.
Schriver, David↗
Simulation and non-linear stage of the electrostatic waves observed during the AMPTE lithium release in the solar wind
During the AMPTE lithium releases in the solar wind intense electrostatic waves with frequencies between a few tens of Hz to several kHz were observed outside the diamagnetic cavity. The results of linear Vlasov theory have suggested that these waves may be generated through two types of instabilities. One is the ion-ion instability associated with the relative drift between the lithium ions and the solar wind protons, and the other is the ion-acoustic instability due to the relative drift between the electrons and the ions. In order to look at the non-linear behavior of the wave-particle interactions, and discern the effect of waves on the particles, full particle electrostatic simulations have been performed, and the results are presented here. It is shown that the ion-ion instability whose phase velocity is oblique to the solar wind velocity can cause considerable anisotropic 'heating' of both the lithium ions and the solar wind protons.
Omidi, N.↗
Simulations of active ion injection experiments on ARCS 3
The ARCS 3 sounding rocket experiment used two argon guns oriented parallel and perpendicular to the geomagnetic field. The parameters of this experiment have been used in a series of particle simulations in order to interpret ion beam interaction with the multispecies ionospheric plasma. Along with the lower hybrid mode between the electron and the hydrogen gyrofrequencies, ion-ion hybrid modes between the hydrogen and helium gyrofrequencies and between the helium and oxygen gyrofrequencies are identified in the simulations. Besides these cold plasma modes, warm Bernstein modes of the respective ion species are identified. The parallel argon beam injections excite lower hybrid waves perpendicular to the magnetic field because of the finite thermal spread of the parallel beam. Perpendicular ion heating of background hydrogen, helium, and oxygen is comparable in the simulations. Comparisons are made with the wave and particle data from the ARCS 3 rocket experiment.
Hudson, M. K.↗
Broadband electrostatic waves as a consequence of magnetotail reconnection
One and two-dimensional particle stimulations are used to study ion beam driven instabilities within the plasma sheet boundary layer (PSBL) and the consequences these instabilities have in terms of plasma heating. It shown that when cold lobe plasma convects into the PSBL and interacts with the ion beams, two wave modes can be driven unstable, the electron acoustic and ion-ion two stream instabilities; these waves heat the cold electrons and cold ions close to plasma sheet temperatures.
Ashour-Abdalla, Maha↗
A theoretical interpretation of upstreaming electrons and elevated conics on auroral field lines
Recent VIKING satellite observations in the auroral zone have shown the association of elevated ion conics (conics with a low energy cutoff above zero) with upward streaming electrons in the presence of low frequency electric field fluctuations. A self-consistent particle simulation was developed which assumed the presence of a steady state electric field on auroral zone field lines capable of accelerating ions up the magnetic field lines. Results from this study show that a low frequency ion-ion two stream instability can be excited. This low frequency instability creates a fluctuating electric field which heats the ions oblique to the magnetic field forming distributions similar to the elevated ion conics. The ion-ion waves also interact resonantly with electrons and accelerates them in the direction of the ion beam.
Ashour-Abdalla, Maha↗
Acceleration of thermal plasma in the magnetosphere
Analytic theory and numerical simulations are used here to investigate the physics of two types of mixed plasmas. The transverse acceleration of ions on auroral field lines is considered in order to determine the effects of multiion species. In the auroral zone the components of a multiion plasma, including hydrogen and oxygen, interact with each other as well as with a two-component electron plasma composed of both a magnetospheric beam and background ionospheric components. This interaction occurs as a mixed ion-ion hybrid mode. How an electron plasma, with both hot and cold components as well as ion beams, affects the plasma sheet boundary layer is examined. It is found that in the presence of this mixed electron plasma, warm ion beams can drive the electron acoustic instability; this phenomenon may be responsible for broadband electrostatic noise in the boundary layer.
Ashour-Abdalla, Maha↗
Properties of large scale plasma flow during the early stage of the plasmaspheric refilling
The objective is to better characterize the macroscopic properties of the interhemisphere plasma flow by solving a more complete set of hydrodynamic equations than that solved previously. Specifically, the ion continuity, momentum and energy equations were solved for the plasma flow along the closed magnetic field lines. During the initial stage of the supersonic outflow in the equatorial region, the ions cool substantially. Using the hydrodynamic model for the large-scale plasma flow, the dynamics of shocks was examined which form in the geomagnetic flux tubes during the early stages of refilling. These shocks are more like those forming in neutral gases than the electrostatic shocks driven by microinstabilities involving ion-ion interaction. Therefore, the shocks seen in the hydrodynamic model are termed as hydrodynamic shocks. Such shocks are generally unsteady and therefore the usual shock jump conditions given by Rankine-Hugoniot relations are not strictly applicable to them. The density, flow velocity and temperature structures associated with the shocks are examined for both asymmetrical and symmetrical flows. In the asymmetrical flow the outflow from one of two conjugate ionospheres is dominant. On the other hand, in the symmetrical case outflows from the two ionospheric sources are identical. Both cases are treated by a two-stream model. In the late type of flow, the early-time refilling shows a relaxation type of oscillation, which is driven by the large-scale interactions between the two identical streams. After this early stage, the resulting temperature structure shows some interesting features. In the equatorial region the streams are isothermal, but in the off-equatorial regions the streams have quite different temperatures, and also densities and flow velocities. The dense and slow stream is found to be warmer than the low-density fast stream. In the late stage of refilling, the temperature is found to steadily increase from the conjugate ionospheres towards the equator; the equatorial temperature is found to be as high as about 8000 K compared to the ionospheric temperature of 3600 K.
Singh, Nagendra↗
H(+) - O(+) two-stream interaction on auroral field lines
Upflowing beams of hydrogen, oxygen, and minor ion species, and downward accelerated electrons have been observed above several thousand kilometers altitude on evening auroral field lines. The mechanism for electron and ion acceleration is generally accepted to be the presence of a quasi-static electric field with a component parallel to the earth's magnetic field. The thermal energy of the observed beams is much larger than ionospheric ion temperatures indicating that the beams have been heated as they are accelerated upward. This heating is probably due to a two-stream interaction between beams of different mass ions. The beams gain equal energy in the potential drop and so have different average velocities. Their relative streaming initiates an ion-ion two-stream interaction which then mediates a transfer of energy and momentum between the beams and causes thermalization of each beam. The qualitative evidence that supports this scenario is reviewed. Properties of the two-stream instability are presented in order to demonstrate that a calculation of the evolution of ion beams requires a model that includes field-aligned spatial structure.
Bergmann, Rachelle↗
Thermophysical properties of simple liquid metals: A brief review of theory
In this paper, we review the current theory of the thermophysical properties of simple liquid metals. The emphasis is on thermodynamic properties, but we also briefly discuss the nonequilibrium properties of liquid metals. We begin by defining a 'simple liquid metal' as one in which the valence electrons interact only weakly with the ionic cores, so that the interaction can be treated by perturbation theory. We then write down the equilibrium Hamiltonian of a liquid metal as a sum of five terms: the bare ion-ion interaction, the electron-electron interaction, the bare electron-ion interaction, and the kinetic energies of electrons and ions. Since the electron-ion interaction can be treated by perturbation, the electronic part contributes in two ways to the Helmholtz free energy: it gives a density-dependent term which is independent of the arrangement of ions, and it acts to screen the ion-ion interaction, giving rise to effective ion-ion pair potentials which are density-dependent, in general. After sketching the form of a typical pair potential, we briefly enumerate some methods for calculating the ionic distribution function and hence the Helmholtz free energy of the liquid: monte Carlo simulations, molecular dynamics simulations, and thermodynamic perturbation theory. The final result is a general expression for the Helmholtz free energy of the liquid metal. It can be used to calculate a wide range of thermodynamic properties of simple metal liquids, which we enumerate. They include not only a range of thermodynamic coefficients of both metals and alloys, but also many aspects of the phase diagram, including freezing curves of pure elements and phase diagrams of liquid alloys (including liquidus and solidus curves). We briefly mention some key discoveries resulting from previous applications of this method, and point out that the same methods work for other materials not normally considered to be liquid metals (such as colloidal suspensions, in which the suspended microspheres behave like ions screened by the salt solution in which they are suspended). We conclude with a brief discussion of some non-equilibrium (i.e., transport) properties which can be treated by an extension of these methods. These include electrical resistivity, thermal conductivity, viscosity, atomic self-diffusion coefficients, concentration diffusion coefficients in alloys, surface tension and thermal emissivity. Finally, we briefly mention two methods by which the theory might be extended to non-simple liquid metals: these are empirical techniques (i.e., empirical two- and three-body potentials), and numerical many-body approaches. Both may be potentially applicable to extremely complex systems, such as nonstoichiometric liquid semiconductor alloys.
Stroud, David↗