Two-component Plasma Research Articles

Heat Transfer In Magnetohydrodynamic (Mhd) Couette Flow Of A Two-Component Plasma With Variable Wall Temperature

In this paper we study the field structure and the heat transfer at the walls of two-component plasma. The flow is induced by two horizontal walls moving relative to each other along their common axis in the presence of a uniformly applied transverse magnetic field and the analysis made under the following assumptions: (i) The flow is viscous and incompressible. (ii) The flow is fully developed. (iii) The temperature varies linearly along the wall. (iv) The temperature difference between the walls is not large enough to cause free convection current to flow. Exact solutions for the velocities and temperatures for the ionized and neutral particles and the induced magnetic field are derived. These together with the heat transfer are discussed quantitatively. Keywords: Couette flow, two-component plasma, field structure, heat transfer, Hartmann number, Magneto hydrodynamic, Nusselt number Global Journal or Pure and Applied Sciences Vol. 14 (4) 2008: pp. 439-449

Collisional energy transfer in two-component plasmas

The friction in plasmas consisting of two species with different temperatures is discussed together with the consequent energy transfer. It is shown that the friction between the two species has no effect on the ion acoustic mode in a quasineutral plasma. Using the Poisson equation instead of the quasineutrality reveals the possibility for an instability driven by the collisional energy transfer. However, the different starting temperatures of the two species imply an evolving background. It is shown that the relaxation time of the background electron-ion plasma is, in fact, always shorter than the growth rate time. Therefore the instability is unlikely to develop. The results obtained here should contribute to the definite clarification of some contradictory results obtained in the past.

Radiation transport of heliospheric Lyman-α from combined Cassini and Voyager data sets

Heliospheric neutral hydrogen scatters solar Lyman-alpha radiation from the Sun with '27-day' intensity modulations observed near Earth due to the Sun's rotation combined with Earth's orbital motion. These modulations are increasingly damped in amplitude at larger distances from the Sun due to multiple scattering in the heliosphere, providing a diagnostic of the interplanetary neutral hydrogen density independent of instrument calibration. This paper presents Cassini data from 2003-2004 obtained downwind near Saturn at approximately 10 AU that at times show undamped '27-day' waves in good agreement with the single-scattering models of Pryor et al., 1992. Simultaneous Voyager 1 data from 2003- 2004 obtained upwind at a distance of 88.8-92.6 AU from the Sun show waves damped by a factor of -0.21. The observed degree of damping is interpreted in terms of Monte Carlo multiple-scattering calculations (e.g., Keller et al., 1981) applied to two heliospheric hydrogen two-shock density distributions (discussed in Gangopadhyay et al., 2006) calculated in the frame of the Baranov-Malama model of the solar wind interaction with the two-component (neutral hydrogen and plasma) interstellar wind (Baranov and Malama 1993, Izmodenov et al., 2001, Baranov and Izmodenov, 2006). We conclude that multiple scattering is definitely occurring in the outer heliosphere. Both models compare favorably to the data, using heliospheric neutral H densities at the termination shock of 0.085 cm(exp -3) and 0.095 cm(exp -3). This work generally agrees with earlier discussions of Voyager data in Quemerais et al., 1996 showing the importance of multiple scattering but is based on Voyager data obtained at larger distances from the Sun (with larger damping) simultaneously with Cassini data obtained closer to the Sun.

Renormalized cluster expansion of the microfield distribution in strongly coupled two-component plasmas

The electric microfield distribution (MFD) at a neutral point is studied for two-component (TCP) electron-ion plasmas using molecular-dynamics simulation and theoretical models. The particles are treated within classical statistical mechanics using an electron-ion Coulomb potential regularized at distances less than the de Broglie length to take into account quantum-diffraction effects. Corrections to the potential-of-mean-force exponential (PMFEX) approximation recently proposed for the MFD at an impurity ion in a strongly coupled TCP [Nersisyan, Phys. Rev. E 72, 036403 (2005)] are obtained and discussed. This has been done by a generalization of the standard Baranger-Mozer and renormalized cluster expansion techniques originally developed for the one-component plasmas to the TCPs. The results from this theoretical model are compared with those from molecular-dynamics simulations. In particular, for a strongly coupled TCP with an ionic charge Z>5 the agreement with numerical simulations is excellent. For still increasing coupling we furthermore found that the PMFEX scheme becomes insufficient to predict the MFD at a neutral point, while its improved version quite well agrees with the simulations.

Potential distributions in dense plasmas composed of degenerate electrons and positive nanoparticles

The test charge potential involving the electron dust acoustic oscillations is computed in a two-component plasma whose constituents are hot electrons and positive nanoparticles. The hot degenerate inertialess electrons are assumed to follow the Thomas–Fermi distribution, while positive nanoparticles are inertial. The expressions for the Debye–Hückel and wake potentials due to a moving test charge are obtained. Furthermore, the effects of the Fermi energy, the number density of the hot degenerate electrons, and the test charge speed on the potential profiles are numerically examined.

Structural features of two-component dusty plasma Coulomb balls

A binary mixture of dust particles in plasma occurring in an external electrostatic spherical confinement field has been numerically simulated. Calculations have been performed within the framework of the molecular dynamics method, with the interparticle forces described in terms of an isotropic Yukawa pair potential. It is shown that the particles form a shell structure, each particular shell consisting of particles of the same kind. The structural properties of such a binary mixture of particles and the specific features of their segregation under the conditions of recent experiments on the formation of Coulomb balls have been studied.

Influence of the radial profile of the electric potential on the confinement of a high-β two-component plasma in a gas-dynamic trap

One of the most important problems to be studied in the gas-dynamic trap (GDT) facility is the investigation of MHD stability and cross-field transport in a plasma with a relatively high value of β = πp/B2. Recent experiments demonstrated that the radial electric field produced in the plasma by using radial limiters and coaxial end plasma collectors improves plasma stability in axisymmetric magnetic mirror systems without applying special MHD stabilizers. The experimental data presented in this work show that stable plasma confinement can be achieved by producing a radial potential drop across a narrow region near the plasma boundary. Creating radial electric fields of strength 15–40 V/cm causes a shear plasma flow, thereby substantially increasing the plasma confinement time. When all the radial electrodes were grounded, the confinement was unstable and the plasma confinement time was much shorter than the characteristic time of plasma outflow through the magnetic mirrors. Measurements of cross-field plasma fluxes with the use of a specially designed combined probe show that, in confinement modes with differential plasma rotation, transverse particle losses are negligibly small as compared to longitudinal ones and thus can be ignored. It is also shown that, when the GDT plasma is in electric contact with the radial limiters and end collectors, the growth rate of interchange instability decreases considerably; such a contact, however, does not ensure complete MHD stability when the electrodes are at the same potential.

Guest Charge and Potential Fluctuations in Two-Dimensional Classical Coulomb Systems

A known generalization of the Stillinger-Lovett sum rule for a guest charge immersed in a two-dimensional one-component plasma (the second moment of the screening cloud around this guest charge) is more simply retrieved, just by using the BGY hierarchy for a mixture of several species; the zeroth moment of the excess density around a guest charge immersed in a two-component plasma is also obtained. The moments of the electric potential are related to the excess chemical potential of a guest charge; explicit results are obtained in several special cases.

Classical and quantum Coulomb crystals

Strong correlation effects in classical and quantum plasmas are discussed. In particular, Coulomb (Wigner) crystallization phenomena are reviewed focusing on one-component non-neutral plasmas in traps and on macroscopic two-component neutral plasmas. The conditions for crystal formation in terms of critical values of the coupling parameters and the distance fluctuations and the phase diagram of Coulomb crystals are discussed.

Ion-acoustic solitary waves in fully relativistic electron-ion plasmas

The possibility of ion-acoustic solitary waves in a fully relativistic plasma comprised of electrons and ions is investigated by the pseudopotential method. Applying the gas-dynamic approach developed by McKenzie [Phys. Plasmas 9, 800 (2002)] to the energy conservation laws, it is shown that, as in nonrelativistic plasmas, only compressive ion-acoustic solitary waves are possible in two-component relativistic plasmas in the case where the ions are supersonic and electrons are subsonic. It is also shown that, by introducing the relativistic ion-acoustic velocity, various existence conditions for the solitary waves in relativistic two-fluid plasmas can be cast into forms that are identical to the nonrelativistic counterparts found by the gas-dynamic approach. It can be suggested that the method presented in this study can be extended for the investigation of other kinds of electrostatic solitary waves in relativistic multicomponent plasmas.

Wave kinetic description of quantum pair plasmas

AbstractThe dispersion relation for a quantum pair plasma is derived, by using a wave kinetic description. A general form of the kinetic dispersion relation for electrostatic waves in a two-component quantum plasma is established. The particular case of an electron–positron pair plasma is considered in detail. Exact expressions for Landau damping are derived, and the quasi-classical limit is discussed.

Timelike boundary sine-Gordon theory and two-component plasma

It has long been known that there is a relation between boundary sine-Gordon theory and thermodynamics of charge neutral two-component Coulomb plasma on a unit circle. On the other hand, recently it was found that open string world sheet description of brane decay can be related to a sequence of points of thermodynamic equilibrium of one-component plasma. Here we consider a different decay process which is specifically described by the timelike boundary sine-Gordon theory. We find time evolution to be mapped to a one-dimensional curve in the space of points of thermal equilibrium of a non-neutral two-component Coulomb plasma. We compute the free energy of the system and find that along the curve it is monotonically decreasing, defining a thermodynamic arrow of time.

Parallel TREE code for two-component ultracold plasma analysis

The TREE method has been widely used for long-range interaction N-body problems. We have developed a parallel TREE code for two-component classical plasmas with open boundary conditions and highly non-uniform charge distributions. The program efficiently handles millions of particles evolved over long relaxation times requiring millions of time steps. Appropriate domain decomposition and dynamic data management were employed, and large-scale parallel processing was achieved using an intermediate level of granularity of domain decomposition and ghost TREE communication. Even though the computational load is not fully distributed in fine grains, high parallel efficiency was achieved for ultracold plasma systems of charged particles. As an application, we performed simulations of an ultracold neutral plasma with a half million particles and a half million time steps. For the long temporal trajectories of relaxation between heavy ions and light electrons, large configurations of ultracold plasmas can now be investigated, which was not possible in past studies.

Two-Dimensional Two-Component Plasma with Adsorbing Impurities

We study the behavior of the two-dimensional two-component plasma in the presence of some adsorbing impurities. Using a solvable model, we find analytic expressions for the thermodynamic properties of the plasma such as the $n$-body densities, the grand potential, and the pressure. We specialize in the case where there are one or two adsorbing point impurities in the plasma, and in the case where there are one or two parallel adsorbing lines. In the former case we study the effective interaction between the impurities, due to the charge redistribution around them. The latter case is a model for electrodes with adsorbing sticky sites on their surface.

Collective and static properties of model two-component plasmas

Classical MD data on the charge-charge dynamic structure factor of two-component plasmas (TCP) modeled in Phys. Rev. A 23, 2041 (1981) are analyzed using the sum rules and other exact relations. The convergent power moments of the imaginary part of the model system dielectric function are expressed in terms of its partial static structure factors, which are computed by the method of hypernetted chains using the Deutsch effective potential. High-frequency asymptotic behavior of the dielectric function is specified to include the effects of inverse bremsstrahlung. The agreement with the MD data is improved, and important statistical characteristics of the model TCP, such as the probability to find both electron and ion at one point, are determined.

Electrostatic electron cyclotron harmonic waves observed by the Akebono satellite near the equatorial region of the plasmasphere

Abstract Analysis of the plasma wave observation data provided by the plasma waves and sounder experiment (PWS) on board the Akebono satellite frequently reveals the presence of electrostatic electron cyclotron harmonic (ESCH) waves in the low-latitude region (MLAT < 45°) of the plasmasphere within an altitude range from about 3000 km to the apogee of the satellite (initial apogee was 10,500 km). Even at moderate or low geomagnetic activity, intense ESCH waves often appear near the equatorial region of the plasmasphere above the upper hybrid resonance (UHR) frequency at the lowest harmonic number branch of the f Qn ESCH waves. We identified these plasma waves as the equatorial plasmasphere f Qn waves (EP-f Qn). The spectra of the EP-f Qn waves are characterized by a narrow band structure and by a strong nature, with a wave intensity that ranges from 3.46 × 10-8 to 3.31 × 10-4 V/m. The maximum intensity is nearly coincident with the upper limit of the PWS receiver in the low-gain mode. Statistical analysis results reveal that the EP-f Qn waves are observable in all the local time sectors; however, the occurrence probability shows a clear enhancement in the early morning sector of 01–03 MLT in the plasmasphere. The EP-f Qn wave activities are suppressed within a period of strong magnetic disturbances as well as solar minimum phase. The linear dispersion relation analysis using a two-component plasma model reveals that supra-thermal plasma with the energy of about 750 eV and with a large temperature anisotropy (A = T-perp/T-parallel–1 > 40) must be present in order to realize an appearance of a positive growth rate at the observed frequency and propagation angle of the ESCH waves. Since the hot plasma with such a high anisotropy has not been detected, the validity of the present two-component plasma model remains an open question. The occurrence feature of the ESCH waves showed that there is a constant activation or a constant flow-in of free energy to generate the strong plasma instability of ESCH waves near the post-midnight sector of the plasmasphere. The existence of ESCH waves revealed that the nature of the plasmaspheric plasma is more turbulent and active than has been believed.

Generation of magnetic fields in a positive–negative dusty plasma

Abstract.It is shown that purely growing magnetic fields in a two-component dusty plasma can e generated due to the equilibrium drift of positive and negative dust grains. For this purpose, a linear dispersion relation has been derived by using the hydrodynamic equations for the charged dust fluids, the Maxwell equation and Faraday' law. The dispersion relation admits a purely growing instability, the growth rate of which is proportional to the equilibrium streaming speeds of positive and negative dust grains. A possible physical explanation for the instability is offered. Applications of our investigation to magnetic fields in the thin Martian environments, interplanetary spaces and dense molecular clouds are mentioned.

Effectivity of the modified two stream instability operating in the vicinity of Venus

This paper is devoted to the application of the modified two stream or cross current instability (MTSI) to the interaction of the solar wind and Venus. Two scenarios are presented providing favorable conditions for the excitation of the instability. For the first scenario, the free energy source of the MTSI is a significant gradient drift of the solar wind protons near the subsolar ionopause. The corresponding growth rates and frequencies of the MTSI are calculated within a full electromagnetic approach for a two-component plasma. The driving source of the second considered scenario consists in the relative drift velocity between solar wind and planetary particles. For modelling this situation, the dispersion equation for a four-component plasma is solved numerically.

Influence of Radial Electric Field on High-Beta Plasma Confinement in the Gas Dynamic Trap

One of the most important subjects of the GDT research program is MHD-stability and transversal transport of high pressure two-component plasma. Positive influence of radial electric field on the plasma confinement was demonstrated in previous experiments on the GDT in regimes without any special MHD stabilizers. In recent experiments it was observed that stable plasma confinement always corresponds to intermittent distribution of biasing potential on limiters and plasma dumps. It was shown that enhancement of plasma confinement time corresponds to the radial electric field in the range of 15-40 V/cm and one induces the sheared plasma rotation. Regime with grounding of all radial electrodes was typically unstable with plasma confinement time two times lower than gas dynamic flow time. Therefore sheared rotation can stabilize MHD modes of high β two-component plasma in the GDT experiment. It is also shown that contact between plasma and radial electrodes is essential but can not completely provide MHD stability in GDT.Measurements using special combined probe were carried out to study fluctuation induced transversal transport and allowed to conclude that cross field transport is negligible and does not play essential role in regimes with sheared plasma rotation.

Effects of charge and mass variations on the structure in 2D one-component and two-component dusty plasmas**Supported by the National Natural Science Foundation of China under Grant No. 10547121 and 10175036.

Using molecular dynamics simulation, we calculate the mean square displacement, the pair correlation function, the velocity autocorrelation function and the spectrum function of a two-dimensional (2D) charged dust system. Results show that the critical coupling constant Γ* for the phase transition from a liquid-like state to a solid-like state decreases with increasing charge and mass of particles in the one-component system. A scaling relation between Γ* and μ (Γ* ∝ μ−1.72±0.07) is given, where μ represents the quantities of charge and mass. In the system with two species of particles, the coagulation process is found to be delayed by the presence of one species, and Γ* is closer to that of the ‘smaller’ particles species, which has the smaller charge and mass.