bluuebunny/crossref_metadata_2025 huggingface dataset:
Low Mach Number Magnetic Compression Waves in a Collision-Free Plasma
Authors: Auer P. L. , Hurwitz H. , Kilb R. W.
Published: December 2004

The development of a strong hydromagnetic disturbance traveling perpendicular to an initially uniform magnetic field in a cold plasma is investigated by numerical integration of the equations of motion. The disturbance is driven by an electric field applied at a fixed plane surface which coincides with the initial boundary of the plasma. If the Mach number of the resulting disturbance is less than two, no crossing of particle orbits occurs. The disturbance then consists of a growing train of almost independent hydromagnetic pulses progressing into the undisturbed plasma at a speed somewhat in excess of the shock velocity which would be calculated from classical theory. The magnitudes of the vacuum magnetic field and the vacuum-plasma interface velocity are, however, almost identical to the predictions of classical theory. These results, as well as the observed pulse spacing, can be understood in terms of a two-region model of the disturbed portion of the plasma together with the assumption that the pulses are accelerated by mutual interaction until their spacing substantially exceeds their width.
Interaction of Low-Frequency Electromagnetic Waves with a Plasma
Authors: Turcotte Donald L. , Schubert Gerald
Published: December 2004

The interaction of a low-frequency electromagnetic wave with a semi-infinite plasma is considered. The single-fluid equations of magneto-gas dynamics are linearized in the presence of a strong, uniform, steady magnetic field. Solutions are obtained for both normal incidence and parallel propagation of the electromagnetic wave. In both cases the strong, steady magnetic field is parallel to the interface and the magnetic component of the incident wave has the same direction. In the examples con-considered, the parameter μ02σ0H02/ρ0ω determines the interaction between electromagnetic and acoustic modes. With normal incidence an acoustic mode is excited if this parameter is of order one. In the case of parallel propagation an appreciable parallel velocity component is excited when the governing parameter is quite small.
Molecular Beam for the Study of High-Temperature-Gas Collision Processes
Authors: Skinner George T.
Published: December 2004

A high-intensity molecular beam is described, in which a tailored-interface shock tube is used as the gas source. The purpose of the apparatus is to extend molecular beam techniques into the 1–10 ev per particle range, in order to study collision processes in high-temperature gases. The principles of the apparatus are discussed. Experimental intensity profiles agree with the predicted profiles. A 0.7-ev nitrogen beam was produced in experiments which were designed to determine whether high-intensity high-energy beams could be obtained when the stagnation temperature of the gas in an order of magnitude higher than the apparatus temperature.
Unified Rheological Relation of Non-Newtonian Fluids
Authors: Chang Chieh C. , Ramanaiah P.
Published: December 2004

A new phenomenological formulation of a unified rheological relation of non-Newtonian fluids is described. This relation checks very closely for many non-Newtonian fluids. As a first approximation, a power law of velocity gradient representing viscosity is also derived for the intermediate range between the upper and lower limits of viscosity.
On the Angular Distribution of Cyclotron Radiation from a Hot Plasma
Authors: Trubnikov B. A.
Published: December 2004

It is shown that the formula of Drummond and Rosenbluth for the angular dependence of the absorption coefficient of cyclotron radiation from a hot plasma is too crude, and hence the numerical estimates based on this formula for the total radiation from a plasma layer turn out to be less valid than the previous results obtained by the present author.
Thermalization of a Fast Ion in a Plasma
Authors: Kranzer Herbert C.
Published: December 2004

The question of the precise rate of thermalization of a fast ion in a plasma is of some interest in connection with several existing or proposed controlled thermonuclear devices. In this paper we follow a fast ion which is injected into a plasma in equilibrium. Specifically, we determine the time history of the probability distribution of this ion in velocity space. This is done by numerical integration of the linearized, space-independent Fokker-Planck equation with both the ion-ion and ion-electron interaction terms retained. The mean time of thermalization is calculated for several widely separated injection velocities. Some other properties of this single-ion probability distribution are analyzed.
Low-Density Shock Tube for Chemical Kinetics Studies
Authors: Lin Shao-Chi , Fyfe Walter I.
Published: December 2004

Some problems concerning the extension of high-temperature shock tube experiments to low gas densities are discussed. Specific examples are cited on the operation and actual performance of a 24-in. diam shock tube that has been constructed for chemical kinetics studies at gas densities in the neighborhood of 10−5 normal atmosphere (i.e., about 80 km simulated altitude). Some preliminary results on the dissociation and ionization rates, as well as the visible radiation profile, behind strong normal shocks in air (12 < Ms < 22) at these low densities are also presented.
Dissociated Laminar Boundary Layers with Heterogeneous Recombination
Authors: Fox Herbert , Libby Paul A.
Published: December 2004

A method of systematically treating a variety of laminar boundary layers with surface reaction is presented. With the assumption of simplified transport properties, the solution for the surface concentration in a reaction of any order and with any distribution of surface catalyticity is shown to be given by an integral equation which is amenable to numerical treatment by iteration techniques. The nonlinear boundary condition is shown to be readily handled by the iterative procedure. Certain special cases are discussed. In addition, it is shown how the first-order effects of deviations from simplified transport properties can be readily computed again in terms of integral equations. In the concluding section several illustrative applications of the analysis are presented.
Effect of Radiative Transfer on a Sound Wave Traveling in a Gas having γ near One
Authors: Moore F. K.
Published: December 2004

It is shown that the assumption of specific heat ratio near one simplifies the analysis of plane sound waves subject to energy addition dependent on temperature, and in the case of radiative energy exchange in a fairly transparent gas, a third-order differential equation is obtained. Analytical solutions for a hot and a cool gas are presented which give the complete history of velocity and temperature profiles when a wave is produced by an impulsively started piston, with either a black or reflecting face.

In a very hot gas, an optically thin wave which is thermally dominated by the piston face (or the undisturbed gas, if the face is perfectly reflecting) disperses as though by relaxation and is followed by an optically thick wave, which is thermally independent of the piston and disperses as though by conduction. Transition between thin and thick waves is accomplished in a temperature boundary layer. In a cool gas, dispersion occurs as though by simple radiative heat conduction.

Finally, it is remarked that dispersion in a transparent gas would be observed on the scale of a meter only if the gas is very hot.
Effect of Resonant Charge Exchange on Heat Conduction in Plasmas
Authors: Mason E. A. , Sherman Martin P.
Published: December 2004

Estimates are made of cross sections for symmetric resonant charge exchange between ions differing by one electronic charge. At thermal energies and electron densities of interest, these cross sections are negligible compared to the elastic screened Coulomb cross section for diffusion. It is concluded that resonant charge exchange between ions cannot affect heat conduction in plasmas by controlling the rate of diffusive transport of ionization energy, in contrast to ion-neutral exchange in partially ionized gases.
Curved-Field Plasma Transmission into a Mirror Machine
Authors: Oleson Norman L. , Steinhaus James F. , Barr William L.
Published: December 2004

Plasma from an occluded-gas hydrogenated titanium-washer source was transmitted into a mirror machine along the field lines of a magnetic cusp formed at one end of the system. The results are compared with those produced by an identical gun located at a mirror on the magnet coil axis. Measurements indicate that in low magnetic fields, heavy ions strike the walls, producing neutrals that are subsequently excited and ionized by the contained plasma. At high magnetic fields (∼6 kG at the mirrors), all ions appear to turn the corner but a radial profile of the ion density is asymmetric. A peak density of 1 × 1013 H ions/cm3 is indicated near the mirror axis, agreeing with the results found by other investigators with toroidal or double-bend magnetic field geometries.
Confinement of Plasma Heated by Ion Cyclotron Resonance in the C Stellarator
Authors: Pease R. S. , Yoshikawa S. , Eubank H. P.
Published: December 2004

Microwave interferometric measurements of electron density, measurements of the particle flux to the divertor and of electron and ion cooling rates, have been used to obtain confinement times τc of deuterium plasma (Te up to 80 eV, Ti up to 200 eV, and mean density 0.5 to 5 × 1012 cm−3) in the C stellarator. These times are consistent with a Bohm-type pumpout law, τc = 10−8 2πr02 B/Te sec, where B is in G, r0 (plasma radius) in cm, and Te in eV, and are found to be insensitive to shear, to Ti, and to longitudinal current density with associated drift velocity in the range 0.2 to 7 times the plasma acoustic velocity. The enhancement of plasma temperature produced by ion cyclotron heating is accompanied by enhanced fluctuations in the frequency range of 10 kc/sec to 1 Mc/sec. The particle loss calculated from the fluctuations seems consistent with the measured value of τc, although the measured τc may be determined by other effects, such as the scrape-off layer effect. No improvement in respect of confinement or of fluctuations was detected in a minimum-average-B geometry of 1% well depth. The plasma confinement may have been limited by the lack of detailed toroidal equilibrium. Theoretically, the plasma is unstable both to the universal and to the resistive and kinetic ballooning modes within the observed frequency range and with growth rates within the plasma duration.
Measurements of the Brownian Motion of a Particle in a Gas
Authors: Elrick R. M.
Published: December 2004

A method is outlined for photographing the microscopic fluctuations of submicron particles in a gas. These fluctuations, measured in two orthogonal directions, are shown to be essentially Brownian in character. However, an anisotropy of the motion was observed for smoke particles and an oil drop.
Harmonic Response due to Compressibility in Traveling Wave Plasma Devices Possessing Cylindrical Symmetry
Authors: Haldeman Charles W.
Published: December 2004

When the slip velocity between magnetic field and plasma in a traveling wave induction plasma accelerator exceeds the sonic speed, magneto-acoustic resonances are predicted by linear theory. These resonances are discussed in the case of cylindrical symmetry.
Alternative Method for Exciting Electron Plasma Oscillations with Transverse Electromagnetic Waves
Authors: Montgomery David , Alexeff Igor
Published: December 2004

A shock-like excitation of electron plasma oscillations is proposed which involves no mechanical contact with the plasma. It is achieved by the nonlinear (nonresonant) action of an electromagnetic wave.
Characteristics of a Rotating Plasma
Authors: Hassan H. A.
Published: December 2004

It is shown that a simple consideration of the conservation equations of the plasma constituents explains the characteristics of a rotating plasma observed by Alfvén and Fahleson.
Image Converter Observations of the Development of the Dense Plasma Focus Discharge
Authors: Mather J. W. , Williams A. H.
Published: December 2004

A multiplicity of radial striated light filaments is observed at the back plate of the dense plasma focus coaxial discharge during the early phases of breakdown and current sheath buildup. Later in time, the current sheath appears azimuthally symmetric.
Invariants in Turbulent Flow
Authors: Lumley J. L.
Published: December 2004

As suggested by Phillips, it is shown that in inhomogeneous turbulent flow certain integrals are invariant which are related to the Loitsianskii integral. Under appropriate circumstances, the Loitsianskii invariant is restored (when properly interpreted).
Moving Striations in the Argon Positive Column. II. Experiments
Authors: Gentle Kenneth W.
Published: December 2004

A dc argon discharge is operated with gas flowing opposite to the phase velocity of naturally occurring striations. For a range of gas flows, the striations appear stationary in the laboratory frame. Identifying gas velocity with phase velocity and measuring the wavelength determines the striation dispersion relation in the range of stationarity. Observations were made in a tube of 1-cm diameter, at 5–20 Torr pressures and 30–300 mA currents. The experimental results for a pressure of 10 Torr are compared with the theoretical calculations. Satisfactory agreement is found, especially considering that large-amplitude waves are compared with a linear model. Microwave measurements of the electron temperature and density variations in the striations are presented.
Electron and Ion Transport across a Magnetic Field in an Arc Diffusion Experiment
Authors: Schwirzke Fred
Published: December 2004

The effective ion-diffusion coefficient can be determined from the radial density profile, which in a plasma of finite length is given by the ion transport across and unhindered ion losses along the magnetic field to the conducting end walls. In addition, the electron-diffusion coefficient can be determined from the electron-temperature profile, which depends on the diffusion rate of electrons across the magnetic field, energy dissipation by collisions, and particle losses to the end walls. The measured electron-temperature profile is considerably flatter than expected from collisional diffusion and agrees with the one calculated for Bohm diffusion. The electron-temperature gradient causes a radial electric field which contributes to the ion transport across the field. Taking the ion mobility term into consideration, it is possible to explain the apparent large ion-diffusion coefficients in previous arc diffusion experiments, which were deduced by neglecting electron-temperature gradients and radial electric fields.
Interaction of Plasmons
Authors: Chang David B. , Drummond William E.
Published: December 2004

The nonlinear interaction between plasma oscillation normal modes is studied in a hydrodynamic approximation. A modified quasilinear treatment is used, in which the normal modes are taken to affect each other through the slow nonlinear temporal and spatial changes they induce in the (equilibrium) background quantities. Plasmons, i.e., wave packets of plasma oscillations, are found in this approximation to have an interaction similar in form to the electromagnetic interaction. The plasmon interaction is describable in terms of scalar and vector potentials which satisfy wave equations of the form satisfied by their electromagnetic counterparts. Here, quantities proportional to the slow changes induced in the background number and current densities play the roles of the scalar and vector potentials, with the thermal velocity corresponding to the speed of light. The source terms in the potential wave equations are quadratic in the normal mode density perturbation. The normal mode density perturbation in turn satisfies a Klein-Gordon-like equation, so that, normalized, it would appear to play a role similar to the quantum-mechanical probability wave function Ψ. The nonlinear interaction leads to an instability with a growth rate proportional to the square root of the ratio of the plasma oscillation energy to the background thermal energy.
Plasma Conductivity and Temperature in a Theta Pinch
Authors: Harris Robert W. , McClintock J. E.
Published: December 2004

Using a new balanced magnetic probe technique the plasma magnetic field in a theta pinch has been measured independently of the drive field. The measurements allow a determination of the total plasma current versus time and the plasma current radius versus time. The current radius determined in this manner agrees well with the visible sheath radius from streak photographs. The measurements also allow determination of the plasma conductivity in the sheath, as well as the leakage of trapped flux through the sheath. Temperatures have been calculated from the conductivity, using the ``weak field'' and ``strong field'' conductivity expressions. An independent spectroscopic temperature measurement for the same plasma is consistent with the ``weak field'' conductivity expression. Finally, it is shown that the apparent validity of the ``weak field'' expression is consistent with the average magnetic field strength within the sheath.
Closed Form for the Perturbation Terms of the Linear Boltzmann Equation
Authors: Kohlberg Ira , Siegel Armand
Published: December 2004

A method of solution for the linear Boltzmann equation is presented which expresses the propagator of the equation as a power series of the ``smallness parameter'' of the increments of the random variable, with each term of the series in closed form.
Transition in the Incompressible Wake of a Cone at Low Reynolds Numbers
Authors: Wehrmann O. H.
Published: December 2004

The incompressible wake behind a cone has been studied, and a different shedding frequency law as compared to that of Goldburg and Florsheim has been found.
Mass Spectrometric Observation of Ions Formed during Shock Wave Heating of Gaseous Krypton and Xenon
Authors: Creswell R. , Di Valentin M. A. , Dove J. E.
Published: December 2004

Mass spectrometric analysis of ions sampled directly from shock waves in krypton and xenon at 3600 to 7800°K shows that the principal ion is usually Kr+ or Xe+, but impurity ions are also prominent.
Linearized Initial Value Problem for a Gas
Authors: Buckner John K. , Ferziger Joel H.
Published: December 2004

A complete set of eigenfunctions of the linearized modeled kinetic theory Boltzmann equation appropriate to the initial value problem is constructed. These functions may be used to solve the initial value problem with arbitrary initial conditions and may find application in the construction of the correlation functions required for the analysis of slow-neutron scattering experiments.
Shock-Wave Structure in a Gas Containing Ablating Particles
Authors: Nayfeh Ali Hasan
Published: December 2004

The one-dimensional equations governing the structure of a shock wave in a mixture of a gas and an ablating dust using the transfer properties for free molecular flow are derived. The analysis takes into account the simultaneous effects of the solid particle drag, convective heat transfer, and ablation. These equations are programmed for numerical solution on an IBM 7094. The output of the program is flow properties as functions of the distance behind the shock. The results show that the relaxation distance decreases as the dust mass fraction increases. The pressure, velocity, and temperature in the equilibrium region (i.e., where the dust is completely vaporized, but not chemically reacted) are also obtained by globally conserving mass, momentum, and energy. These results are in reasonable agreement with those obtained from the numerical integration of the full equations. The equilibrium values are applied to the flow in a shock tube. The results show that the presence of the dust increases the driving pressure ratio needed in a shock tube to attain a given shock speed.
Pressure Wave Generation in a Fissioning Gas. IV. Analysis by the Method of Characteristics
Authors: Podney Walter N. , Smith Harold P. , Oppenheim A. K.
Published: December 2004

Nonsteady, one-dimensional, fissionable gas motion induced in a semi-infinite, cylindrical tube of constant cross section by a spatially uniform neutron pulse, irradiating an initial segment of the tube, is formulated in terms of the method of characteristics, and a numerical solution describing the motion, prior to development of strong shock discontinuities, is obtained by finite differences with the use of an IBM 7094 computer. Resulting pressure pulses are compared with those obtained from a ``bulk expansion'' model, which assumes spatial uniformity within the irradiated gas. Although physical validity of this model has been ascertained by a satisfactory agreement between the two, an improved version, in the form of a ``constant pressure gradient,'' model is proposed. Pressure pulses predicted by these models, which neglect wave interactions, are accurate for neutron pulse widths of the order of twice the irradiation length divided by the initial sound speed in the undisturbed gas.
Evaluation of Tietjens Function in Stability Calculations
Authors: Chen T. S. , Joseph D. D. , Sparrow E. M.
Published: December 2004

Tietjens function is re-expressed as a ratio of rapidly converging power series of its (complex) argument which may be utilized to replace tables or graphs in the calculation of critical Reynolds numbers from asymptotic theory.
Longitudinal Plasma Waves in the Low-Frequency Limit
Authors: Parker Lee W.
Published: December 2004

In a partially ionized gas, two longitudinal wave modes propagate at high frequencies, the ion-acoustic mode and the neutral-acoustic mode. At very low frequencies, there are also two roots of the dispersion relation, one representing a damped wave and one representing an undamped wave. If the roots are traced as a function of frequency from the high-frequency regime to the low frequencies, the identification of the roots depends on the ratio of concentrations of ionized and neutral particles. In the low-frequency limit, either the ion wave is damped or the neutral wave is damped, depending on the value of this ratio. The critical value is derived.
Steady-State Structure and Low-Frequency Oscillations of an Infinitely Long E Layer
Authors: Enoch Jacob
Published: December 2004

The time-independent self-consistent equilibrium structure of an infinitely long E layer of finite thickness is investigated by expanding the current density and the magnetic field in powers of the ratio of the layer thickness to its radius. Time-dependent perturbations of the equilibrium solution are studied via the linearized Vlasov equation and a dispersion relation for frequencies well below the cyclotron frequency of the electrons in the total magnetic field is obtained. For perturbations of the form ∼ei(θ−ωt), two roots of this dispersion relation exist. One of these is equal to the experimentally observed precession frequency of the E layer.
Electrical Precursors of Ionizing Shock Waves
Authors: Appleton J. P.
Published: December 2004

Electrical precursors in the immediate vicinity of ionizing shock waves in argon have been examined using a simplified model which describes the mechanism of electron diffusion through the shock. The solutions demonstrate the existence within the translational shock of a charged double layer where the electric field intensity may rise to peak values of several hundred volts per centimeter. The magnitude of the electron densities obtained at the shock front are not inconsistent with those required by Pipkins' analysis which predicts the main features of experimentally observed electron precursors at relatively large distances ahead of the shock. A dicussion of precursors produced by photoionization is included together with a simple demonstration which shows that an impurity such as oxygen, present in concentrations of only one part per million, could be photoionized and thus explain the electron and ion densities recently observed in the region ahead of moderately strong shocks in argon.
Comparison of Closure Approximation Theories in Turbulent Mixing
Authors: Lee Jon
Published: December 2004

Using various closure approximation theories, the evolution of scalar quantity spectrum in a statistically stationary isotropic turbulent velocity field is investigated to provide a unified comparison at Peclet number of 50. The phenomenological Heisenberg (eddy diffusivity) transfer function and the analytical approaches including the truncation, the quasi-normal, and the recent direct-interaction closure approximations are examined. As already known, the truncation and quasi-normal closures result in a negative-spectrum within short decay times. A modified quasi-normal closure formula is suggested as a means of approximating the simultaneous covariances, and the results thereof are comparable with the direct-interaction counterparts.
Brillouin Scattering by Gases as a Test of the Boltzmann Equation
Authors: Nelkin Mark , Yip Sidney
Published: December 2004

The frequency distribution of monochromatic light scattered by a gas is proposed as an experimental test of kinetic theory away from the hydrodynamic regime. The phenomenon is closely analogous to high-frequency sound propagation and is governed by the same linearized Boltzmann equation. The problem can be posed as an initial value problem in an infinite medium. The exact numerical solutions for Maxwell molecules of the preceding paper give an estimate of the results to be expected.
Desorption Rates of Two-Component Gas Mixtures from an Adsorbent Bed
Authors: Penner S. S. , Lauer J. L. , McElmury S. S.
Published: December 2004

Theoretical expressions for the discharge rates of multicomponent gas mixtures through a de Laval nozzle from a closed chamber containing an adsorbent bed are calculated by using an extension of earlier studies on one-component systems. Representative experimental measurements on two-component systems have been interpreted on the assumption that one of the constituents is not adsorbed appreciably. Proper utilization of the theoretical formulas requires simultaneous measurements of gas pressure and composition as a function of time.
Slip Flow of Linearized Couette Problem
Authors: Pao Young-ping
Published: December 2004

An asymptotic solution, valid throughout the physical space, is obtained for the linearized Couette problem at small Knudsen number. The error introduced by this solution is of the order of (1/α) exp [−(1/β)α2/3] where (1/α) is the Knudsen number and β is any real number greater than unity.
Nonuniform Hypersonic Flow past a Wedge
Authors: George A. R.
Published: December 2004

One effect of vorticity in hypersonic flow fields is examined. The problem treated is the inviscid hypersonic flow of a nonuniform incident stream over a wedge. The effects of small spanwise gradients in the incident parallel stream are obtained as a perturbation of ordinary hypersonic wedge flow. The problem is reduced to a rotational conical flow partly bounded by an unknown curved perturbed shock wave. A singular integral equation for the shock shape perturbation is derived and solved. The flow properties behind the shock and at the wedge surface are found and compared to the uniform flow over a variable thickness wedge and to a supersonic potential flow analysis of nonuniform flow. The contrasting results give some insight into the strong influence of the vorticity introduced by curved shocks in hypersonic flow fields.
Some Kinematical Models for Small-Scale Solar Magnetic Fields
Authors: Clark Alfred
Published: December 2004

Kinematical hydromagnetic theory is used to study the magnetic fields produced by the action of two prescribed, steady two-dimensional velocity fields on initially weak, large-scale magnetic fields. In both flows, the magnetic field becomes concentrated along certain vertical planes. In an effort to approximate one aspect of solar photospheric flows, it has been assumed that the fluid motions occupy only a lower half-space, so that a horizontal plane of zero mass flux separates a lower region in motion from an upper one at rest. The magnetic field lines cross this boundary, so that the concentration of the field by the flow is opposed by the tendency of the field above the flow to spread. The other factor opposing the field concentration is the diffusive effect of finite conductivity. Both the time-dependent and eventual steady state magnetic fields are considered for various (large) values of the magnetic Reynolds number.
Stability Criteria and the Initial Value Problem for Collisionless Guiding Center Plasma
Authors: Kadish Abraham
Published: December 2004

Necessary conditions for the stability of collisionless, guiding center plasma are derived. These are compared with those obtained by others using assumptions different than those employed here. The derived conditions are shown to be necessary and sufficient for the stability of equilibrium configurations whose distribution functions are bell shaped in the component of velocity parallel to the magnetic field.
Propagation in Plasmas along the Magnetic Field II. Linear Polarization
Authors: Bachynski M. P. , Gibbs B. W.
Published: December 2004

The propagation of incident linearly polarized plane elecromagnetic waves through a helium afterglow plasma along the direction of a static magnetic field has been experimentally investigated. Measurements of the phase and intensity of the components of the electric field transmitted through the plasma in the same orientation as the incident polarization and cross-polarized to the incident polarization have been made. Comparison with theory which includes the losses due to the plasma shows relatively good agreement.
Spatial Variations of Plasma Electron Temperature in a Standing Wave at Microwave Frequencies
Authors: Cronson H. M.
Published: December 2004

Spatial variations in electron temperature produced in a steady state, room temperature plasma by an electromagnetic standing wave are considered both theoretically and experimentally. The field amplitudes treated are strong enough to raise the electron temperature considerably, but are still too weak to cause inelastic collisions. The electron temperature balance equation for a steady state, spatially varying plasma is derived from a two-term expansion of Boltzmann's equation. In the weakly ionized case, the theoretical equations yield a temperature relaxation distance which determines the spatial dependence of the electron temperature in response to the standing wave. This spatial variation in electron temperature was then measured experimentally in an afterglow plasma, and the observed degree of variation agreed with theoretical predictions.
Nonlinear Sum and Difference Frequency Generation in an Inhomogeneous Plasma
Authors: Sodha Mahendra Singh , Kaw Predhiman Krishan
Published: December 2004

An analytical study is made of the nonlinear generation of the sum and difference frequency components in the current density in a plasma due to two alternating electric fields, an electron density gradient and a tempreature gradient. The results of this study have been used in investigating the nonlinear growth of sum and difference frequency waves in a plasma when two electromagnetic waves of different frequencies are propagating along the same direction in it and, also, the magnitude of these frequency components in the reflected wave from a plasma free space interface when the two electromagnetic waves are incident normally on the interface.
Nature of the Neutral State in Surface-Tension Driven Convection
Authors: Vidal A. , Acrivos Andreas
Published: December 2004

The nature of the neutral state in surface-tension driven convection is investigated by means of a classical linearized stability analysis. By solving the characteristic value problem numerically, it is shown that, as assumed before, the neutral state is indeed a stationary rather than an oscillatory one.
Extension of the Penrose Condition
Authors: Weitzner Harold
Published: December 2004

It is shown that the Penrose condition for the existence of plane wave modes that grow exponentially in time in a plasma described by the linearized Vlasov equation and Poisson's equation is necessary and sufficient for the existence of any modes that grow in time in such a plasma.
Experiments on the Plasma flow past Bodies in a Magnetic Field
Authors: Kawashima Nobuki , Mori Sigeru
Published: December 2004

Plasma flows past bodies in a magnetic field are investigated experimentally by the use of a plasma from a plasma gun. The downstream wake of an ordinary hydrodynamic shock wave is observed for a collision-dominant plasma flow. The structure of the shock is investigated in detail for a wedge-shaped conductor. The plasma flow is divided into four regions by three characteristic lines: (1) the shock front, (2) the expansion wave from the tail of the wedge, and (3) the magnetic line of force passing through the tail of the wedge. When a wake of the shock wave interacts with the other wake, they join into one along the magnetic lines of force. Plasma flows past a wave-shaped wall are also investigated. As the plasma flow becomes collision-free, this downstream wake gradually disappears and no collision-free shock wave is observable. When the plasma flow is sub-Alfvénic, a disturbance propagating upstream along the magnetic lines of force is observed.
High-Velocity Plasma Injection into a Cusped Magnetic Field
Authors: Karr H. J. , Osher J. E.
Published: December 2004

The injection and subsequent behavior of a dense (∼3 × 1013/cm3) fast (V̄ ∼ 108 cm/sec) deuterium plasma jet fired from a coaxial plasma gun into a simple biconical cusped magnetic field has been studied. The experiment shows that for sufficiently high cusp fields up to 90% the plasma jet penetrates the entrance cusp and is lost through the ring cusp without being trapped. In the process of injection a part of the ion energy in the plasma jet is found to be transferred to a group of electrons. X rays of up to 220-keV energy are observed from these energetic electrons with a characteristic decay time of up to 1 msec for cusp fields of 8.5 kG. These long duration energetic electrons are found to be accompanied by a variety of slow high momenta impurity ions (e.g., Fe, O, Si, etc.) in transit through the field and lower energy ions trapped for times in essential agreement with theoretical values for a low-β plasma in a simple cusped field. Observations on the plasma potential are also described.
Effects of a Velocity-Dependent Collision Frequency on Wave-Plasma Interactions
Authors: Whitmer R. F. , Herrmann G. F.
Published: December 2004

Two parameters, an effective collision frequency and an effective plasma frequency, are introduced to describe the effects of the velocity dependence of the collision frequency on wave-plasma interactions. Although mathematically related to other parameters previously used, this particular choice has the decided advantage of providing physical insight into the effect of the collision frequency variation. These parameters are calculated from actual cross section data for He, Ne, A, and N2. A discussion is also given of the effect of the velocity dependence of the collision frequency on the electron cyclotron line shape in magnetoplasmas. The introduction of these effective parameters provides a means for understanding the non-Lorentzian line shapes obtained from exact calculations of the absorption coefficients.
Recombination, Ionization, and Nonequilibrium Electrical Conductivity in Seeded Plasmas
Authors: Cool Terrill A. , Zukoski Edward E.
Published: December 2004

New data are presented which provide direct experimental confirmation of the validity of a physical model which has been widely employed to predict the electrical conductivity of dense, two-temperature, seeded plasmas. Experimental measurements of electron temperature, and ionization and recombination rates are presented for partially ionized plasmas of potassium-seeded argon. Experimental conditions were chosen to cover those ranges of interest in connection with proposed magnetohydrodynamic energy conversion devices for which nonequilibrium electrical conductivity measurements have been previously reported, e.g., translational atom temperatures of about 2000°K, total atom densities near 1018/cm3, potassium densities of about 1016/cm3, electron densities from 1013/cm3 to 1015/cm3, and electron temperatures from 2200 to 3500°K. Measured values of electron-electron-ion recombination coefficients for potassium show good agreement with theoretical values based upon the Gryzinski classical inelastic-collision cross-section expressions. Observed ionization rates and relaxation characteristics appear to be adequately explained by a similar formulation for the ionization process.
Finite Larmor Radius Equations for a Plasma
Authors: Ware A. A.
Published: December 2004

The approximate moment equations for a low β plasma obtained by Rosenbluth and Simon are shown to be special cases of the more general equations of Herdan and Liley. The pressure tensor modification is found to arise from an ion heat conduction contribution.
Electric Current Density in an Ionizing Layer
Authors: Rosciszewski Jan
Published: December 2004

The expression for current density was derived using multifluid equations of conservation of momentum and mass for the gas with the finite rate of ionization in a collision dominated regime (ωiτi < 1).
Birth and Decay of Vortices
Authors: Lugt Hans J. , Schwiderski Ernst W.
Published: December 2004

Complete sets of time-dependent solutions for Stokes' slow-motion equations are constructed by means of a generalized separation technique, which was recently introduced and applied by the authors to steady-state flows. Under certain boundary and regularity conditions, such integrals of slow motion can be used to derive solutions of the quasi-linear Navier-Stokes equations in an exact linear manner. The classes of separable solutions, which are presented in this paper, reveal significant mathematical properties of laminar motions concerning their uniqueness and regularity. From the physical point of view, they render valuable information on the mechanism of growing and dying vortices. For instance, it can be shown that a decaying discontinuity line is a process which involves the gradual obliteration of a discrete spectrum of vortices in such a way that little vortices with large damping coefficients dominate first, and that bigger vortices of fewer number replace them with advancing time. Furthermore, the development and decay of singular vortices are investigated.
Nonexistence of Looping Trajectories in Hydromagnetic Waves of Finite Amplitude
Authors: Yeh Tyan
Published: December 2004

It is shown that looping trajectories cannot exist in finite amplitude hydromagnetic waves propagating across a magnetic field in a quasi-neutral cold collision-free plasma.
Flow of a Rarefied Gas in a Tube of Annular Section
Authors: Bassanini Piero , Cercignani Carlo , Sernagiotto Franco
Published: December 2004

The Poiseuille flow of a rarefied gas in a tube of annular section is analyzed numerically for an inverse Knudsen number ranging from 0 to 10. The Bhatnagar-Gross-Krook model is used and the transport integro-differential equation is reduced to a purely integral one, which is solved numerically. The plot of the volume flow rate versus pressure is shown to have the expected minimum; it also fits rather well with experimental data.
Laminar Free Jet with Arbitrary Prandtl Number
Authors: Hug W. F. , Warder R. C.
Published: December 2004

Analytical similarity solutions are determined for the heated two-dimensional laminar free jet with arbitrary Prandtl number and nonlinear viscosity-temperature relationships.
Cartesian Tensor Form of the Magnetohydrodynamic Wave Equation
Authors: Kraut Edgar A.
Published: December 2004

The magnetohydrodynamic wave equation for a compressible infinitely conducting fluid is formulated in Cartesian tensor form. It is shown that the resulting fourth rank Cartesian tensor is singular and thus has no inverse.
Interferometric Measurement of the Nonequilibrium Flow Field around a Cone
Authors: Spurk J. H. , Bartos J. M.
Published: December 2004

Interferometric measurement of the density field around a cone in a stream of oxygen at approximately 10 000 ft/sec is reported. The test flow has been generated in an expansion tube, which utilizes an unsteady expansion for the purpose of total enthalpy multiplication. The experiment shows that vibrational equilibrium is achieved close behind the shock, while chemical relaxation occurs throughout the shock layer. The experimental density distribution and shock shape are compared with theoretical predictions, and good agreement is found.
Certain Periodic Flows of Anisotropic Fluids
Authors: Kaloni P. N.
Published: December 2004

Certain periodic flows of orientable fluids are studied which tend to be unoriented at rest. Consideration is given to the linearized equations only. It is found that linearized equations predict a typical phenomenon of resonance.
Order-Disorder Theory for Liquid He3−He4 Mixtures
Authors: Sreedhar A. K.
Published: December 2004

Assuming that the lambda transition in liquid He4 and in He3−He4 solutions can be described formally on the basis of an order-disorder theory, the thermodynamic behavior of He3−He4 solutions has been analyzed using Bragg-Williams approximation. It is found that the order-disorder formalism accounts for the observed behavior fairly well, especially at low He3 concentrations.
Microscopic Treatment of Classical Containment in the Stellarator
Authors: Bishop A. S. , Smith Craig G.
Published: December 2004

Single-particle containment is investigated for the stellarator by treating the guiding-center orbits of charged particles in the presence of a radial electric field. The domain in velocity space (analogous to the loss cone of mirror devices) for which the orbits lead out of the plasma column is identified. Particle confinement as a function of field strength is presented, and an approximation to the self-consistent, equilibrium field is calculated for a uniform density plasma. The velocity distribution, truncated by the escape of particles from the loss cone, is shown to produce an axial current, both in the presence and absence of the electric field; contours of constant current density are presented for both cases. A method for treating the general case of charged particles moving at all times under the influence of self-consistent electric fields is also presented.
Low-Frequency Waves and Gradient Instabilities in the Ionosphere
Authors: Liu C. H. , Yeh K. C.
Published: December 2004

Low-frequency incompressible waves in the inhomogeneous ionosphere are studied. It is proved that there exists a variational principle which allows the derivation of the dispersion relation by a simple trial solution technique. The dispersion relation shows that when the height gradient is positive and steep there may exist instabilities, and the growth rate is given approximately by gρ / ρν, where g is the gravity, ρ the plasma mass density, ρ′ its height gradient, and ν the ion-neutral collisional frequency. Experimental support of the gradient instability is given.
Mechanism of Radio-Frequency-Induced Plasma Shield Propagation
Authors: Bethke George W. , Ruess Allen D.
Published: December 2004

Microwave-induced ionization wave experiments are described, leading to suggested production and propagation mechanisms.
Ballooning Interchange Instabilities of Magnetized Plasmas under Gravitational Fields
Authors: Yoshikawa S.
Published: December 2004

The relation between the resistive ballooning mode and the ``universal'' type instability with gravitational field (simulating the magnetic field curvature) is discussed. It is shown that under appropriate assumptions, the instability of the ``universal'' type is an extension of the resistive ballooning mode if we replace the collision frequency in the resistive ballooning mode by the effective kinetic collision frequency kzve. The relative importance of these ballooning instabilities to toroidal plasmas is discussed.
Ion Oscillations in a Weakly Turbulent Plasma
Authors: Ichikawa Yoshi H.
Published: December 2004

Ion oscillations in a high-temperature electron-ion plasma with high-frequency turbulent fluctuations are investigated by generalizing the quasi-linear theory to a spatially inhomogeneous system. It is found that the feedback effect of the high-frequency fluctuation on the low-frequency oscillation in the system gives rise to a parametric growth of the ion acoustic mode even if the system has a stable velocity distribution with respect to the ion acoustic mode.
Observations of Instabilities in Electron-Cyclotron Plasmas
Authors: Ard W. B. , Dandl R. A. , Stetson R. F.
Published: December 2004

Two types of instabilities have been studied in an electron-cyclotron plasma confined by magnetic mirrors and heated by continuous wave microwave power at 10.6 Gc. One type of instability results in the loss of energetic electrons (Ee > 100 keV) across magnetic field lines, accompanied by oscillations in the 3–30 Mc range. Suppression of this instability is accomplished by increased background pressure. The second type is characterized by loss of fast electrons along field lines through the magnetic mirrors and accompanied by radio-frequency oscillations at 5.3 Gc (=½ωce). The loss is also characterized by a threshold in magnetic field corresponding to locating the heating zones in the mirror throats. The first type of instability appears to be flute-like and driven by ▿B drifts. The second type may be initiated by the mirror instability in the plasma.
Closure Approximations Applied to Stochastically Distributed Second-Order Reactants
Authors: O'Brien Edward E.
Published: December 2004

The nonlinear problem of the behavior of decaying, isothermal, second-order reactions is posed stochastically. The exact solution, using an initial multivariate normal probability distribution, is compared with various closure approximations that have been employed in the study of turbulence. Kraichnan's direct-interaction hypothesis provides a satisfactory discription of the behavior of single-point functions and of the covariance of the concentration field as does the joint normal distribution hypothesis. However, the former is slightly superior even in this problem in which the energetic difficulties of the latter are not apparent.
Plasma Turbulence and Quasi-Linear Approximation
Authors: Imamura Tsutomu , Taniuti Tosiya
Published: December 2004

A quasi-linear approximation for a turbulent plasma is obtained using the Wiener-Hermite functional expansion for an electric field and a distribution function. Gaussian distributions are obtained with such an approximation.
Energy Density in a Plasma Oscillation
Authors: Ingard Uno , Manheimer Wallace M.
Published: December 2004

The frequency dependence of the electrostatic energy density in an undamped (or weakly damped) longitudinal plasma oscillation and the explicit interrelationship between kinetic, electrostatic, and thermal (compressional) energy density are discussed.
Kinetic Theory of Diffusion in Rarefied Gases
Authors: Ziering S. , Sheinblatt M.
Published: December 2004

In order to investigate diffusion phenomena in rarefied gases, the Boltzmann equation is expanded in Sonine Legendre polynomials in velocity space. It is shown that the flow parameters and transport coefficients are not only functions of the mass and density ratios for a given intermolecular potential, but also depend on ratios of the various mean-free-path's describing the respective like and unlike collisions. The theoretical results are in strict conformity with the standard Chapman and Enskog treatment as a limiting solution in domains where the ratio of scale height to mean-free-path is large. The solution is furthermore analytic for the transition domain, as well as for situations where the two gases are in different flow domains, because of different densities. In addition to the general theory, specific details are worked out for two molecular potentials, namely, Maxwell molecules and rigid spheres.