bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of a Normal Ionizing Shock Wave in Argon
Authors: Perona G. E. , Axford W. I.
Published: February 2004

The structure of normal ionizing shock waves is studied. Following a discussion of some of the work done in this field, the shock equations are integrated for a simple model. The main assumptions are that the effects of viscosity and thermal conductivity are confined to a very narrow region (thermal shock) across which there is no change in ionization, and that the post-shock gas is only slightly ionized. As an example, the equations governing the structure of a shock in argon have been integrated. The results of these calculations justify the use of the assumptions made in deriving the equations.
Equilibrium Correlation Functions for a Two-Component Plasma
Authors: Matsuda Kyoko
Published: February 2004

The equilibrium correlation functions have been calculated for a high-temperature plasma with enough accuracy to yield the thermodynamic functions to second order in terms of the plasma parameter. First, the classical solutions have been obtained for a two-component plasma and a many-component plasma and compared with the results for an electron gas in a uniform positive background. Second, the convergent solutions have been obtained starting with the quantum Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy. In the calculation, exchange effects as well as the Heisenberg effect have been taken into account. Also some corrections of the quantum BBGKY hierarchy concerning the symmetry properties have been given.
Turbulent Diffusion Experiments in a Thermal Plasma
Authors: Porkoláb M. , Kino G. S.
Published: February 2004

Results of a detailed experimental study of turbulent diffusion are presented. The turbulent state is produced in a thermal potassium plasma by (i) injected coherent signals and (ii) injected broad-band noise. Diffusion is found to be directly proportional to the rms amplitude of oscillations, and inversely proportional to the magnetic field intensity. The effect of the oscillation spectrum upon diffusion is also studied. Finally, using the relation eVrms = kT in a Bohm-type diffusion coefficient, numerical estimates are made with the Bohm diffusion coefficient.
Equilibria and Stability of Collisionless Plasmas in Cylindrical Geometry
Authors: Marx K. D.
Published: February 2004

The general equilibrium and neighboring-equilibrium (tearing mode) problems for cylindrical plasma configurations roughly corresponding to the Astron E layer are solved relativistically for a Gaussian velocity distribution function. A family of equilibrium solutions and stability domains is computed for arbitrary E-layer thickness and degree of field-reversal. The solutions have the peculiarity that the equilibrium density is finite (exponentially decaying) at large radii; whereas the tearing mode is always unstable unless a conducting wall is placed at a finite radius. This inconsistency in the analysis is resolved by treating a sharp-edged plasma with a monoenergetic, single-canonical-momentum distribution function.
Nonlocal Reflection in Inhomogeneous Media
Authors: Berk H. L. , Horton C. W. , Rosenbluth M. N. , Baldwin D. E. , Sudan R. N.
Published: February 2004

The physical principle underlying nonlocal wave reflection in a slowly varying spatially inhomogeneous plasma is discussed. In an electrostatically confined system important reflection will arise if there exists points where [∂τ(E, x)/∂E] = 0, where τ(E, x) is the time it takes a resonant particle of energy E at position x to return to the same position. In a mirror field this reflection mechanism can supply sufficiently strong feedback to cause the convectively unstable Post-Rosenbluth loss-cone instability to grow locally in space.
Cyclotron Instability in a Hot Electron Plasma with a Double-Humped Velocity Distribution
Authors: Perkins W. A. , Barr W. L.
Published: February 2004

A high-frequency instability occurring in a “hot electron” plasma (Te ∼ 25 keV; Ne ∼1011 cm−3) contained in a quadrupole-mirror machine (i. e., “minimum-B” field) has been studied experimentally and correlated with theory. The effects observed in the presence of instability bursts are: (1) Intense radiation is emitted at the electron-cyclotron frequency; (2) a short pulse of electrons escapes along the field lines; and (3) the double-humped energy distribution (characteristic of the electrons just before the instability) changes so that the distribution of the hot electron component becomes more nearly Maxwellian simultaneous with a marked increase in the 200-eV component. The experimental observations are compared with the theoretical calculations of Hall, Heckrotte, and Kammash as modified to apply to the measured experimental distributions. In agreement with the observations, these calculations predict the occurrence of an instability at low plasma density, such that ωpe2/ωcp2 ∼ 0.01. In addition, the required presence of a cold electron component, the predicted growth rate of 2 × 107/sec, and the prediction of instability frequencies at ωce are all in agreement with the observations. The present picture is, therefore, that the instability derives from the “loss-cone” nature of the distribution functions of the hot electrons (arising from the fact that they are contained in an open-ended system where scattering into the loss cone is the main loss mechanism), coupled with the presence of a cold electron component.
Plasma Losses in a Toroidal Magnetic Field
Authors: Mah S. Q. , Skarsgard H. M.
Published: February 2004

Plasma losses in a toroidal low-pressure rf discharge have been studied by comparing measured electron temperatures with those predicted by the plasma balance equation. The losses can be attributed to the drift of the partially ionized plasma across the inhomogeneous magnetic field.
Transition Solution for Magnetohydrodynamic Shocks in Arbitrary Fluids
Authors: Lynn Y. M.
Published: February 2004

Parametric representations of transition solution for magnetohydrodynamic shocks in arbitrary fluids are given. Relations governing any downstream parameter and any prescribed shock-strength parameter can be obtained from them after straightforward calculations.
Magnetohydrodynamic Wave Modes behind Normal Ionizing Shock Waves
Authors: Cross R. C. , Gross R. A. , James B. W. , Watson-Munro C. N.
Published: February 2004

The distribution of current loops that develop behind strong ionizing shock waves in a coxial electromagnetic tube has been studied experimentally and found to be similar to modes excited by two dimensional magnetohydrodynamic waves.
Collisionless Plasma Sheath with Transverse Flow
Authors: Hu Pung Nien , Ziering Sigi
Published: February 2004

The previously developed sheath model by the authors is herein extended, so as to include the effect on the sheath structure resulting from a transverse bulk flow in the plasma outside the sheath region.
Effect of the Finite Ion Larmor Radius on the Kelvin-Helmholtz Instability
Authors: Melchior Henning , Popovich M.
Published: February 2004

The Kelvin-Helmholtz instability is described with the effects of the finite ion Larmor radius included. The growth rate is computed for several values of the velocity shear and different density profiles.
Plane Poiseuille Flow of a Rarefied Gas
Authors: Liu C. Y.
Published: February 2004

An analytical solution to the problem of rarefied gas flow in a channel is obtained by the moment method. The expected minimum in volume flow rate is found; the flow rate exhibits an algebraic instead of a logarithmic singularity at low pressures. Present results are compared with the results from other theories and with measurements.
Heat-Transfer and Density-Distribution Measurements between Parallel Plates in the Transition Regime
Authors: Teagan William P. , Springer George S.
Published: February 2004

The heat conduction and density distributions were experimentally determined for rarefied gases at rest contained between two unequally heated parallel plates. Both argon and nitrogen were used as test gases. Particular attention was focused on obtaining measurements in the transition regime where the ratio of plate spacing to mean free path was between 1 and 20. The gas density distribution was measured by observing the luminescence produced by a high-energy electron beam traversed between the plates. The experimental results for argon were compared with the analytical results of Wang Chang and Uhlenbeck, Gross and Ziering, and Lees. In computing these results the thermal accommodation coefficient measured in the free-molecule regime was used with the assumption that its value remained constant over the entire pressure range. The average agreement between the heat conduction data and the results of the four-moment methods of Lees and Gross-Ziering was about 2%, while the measured density profiles agreed with the results of these analyses within 3%. Both the heat conduction and density distribution data differ by ∼10-20% from the results of Gross-Ziering's eight-moment method.
Exact and Asymptotic Master Equations
Authors: Pytte Agnar
Published: February 2004

The exact master equation of Prigogine and Résibois is derived for inhomogeneous as well as homogeneous systems. The asymptotic master equation is obtained from the following postulate: The singularities of the analytically continued Liouville resolvent nearest the real axis are isolated simple poles arising from “irreducible vacuum-to-vacuum” transitions. The asymptotic distribution function found in this way differs from the one obtained previously. If the asymptotic distribution function at time t1, fa(t1) is taken as a new initial value in the exact master equation, and the subsequent asymptotic solution is calculated for a time t2 later, the result is fa(t1 + t2).
Oblique Incidence of an Electromagnetic Wave on a Plasma Layer
Authors: Bowman J. J. , Weston V. H.
Published: February 2004

A plane electromagnetic wave is obliquely incident upon a plasma layer of finite thickness, where the equilibrium plasma is taken to be homogeneous and isotropic. The electric vector of the wave is assumed polarized in the plane of incidence. The specular boundary condition for the distribution function is employed and an exact solution of the coupled Maxwell-Vlasov equations is derived as an expansion in normal modes, yielding coupled tranverse and longitudinal waves in the plasma region. Temperature effects on the reflection coefficient are investigated.
Theory for Cyclotron Harmonic Radiation from Plasmas
Authors: Persson Karl-Birger , Johnson E. G. , Uhlenbrock D. A.
Published: February 2004

A highly simplified hydrodynamic model for the cause of cyclotron harmonics radiation in a magnetized, abnormal-glow, helium plasma is proposed. The high-velocity electrons are treated as sources for the charge density waves in the plasma. Electromagnetic radiation results from interaction of these wake waves with the statistical fluctuations (the granular structure in the ion density). This radiation contains the cyclotron harmonics. Some numerical curves of the radiation spectra are shown for a number of plasma parameters.
Cyclotron Harmonic Emission along the Field from a Plasma
Authors: Wassink Harry W.
Published: February 2004

Electron cyclotron harmonic radiation from an abnormal negative glow plasma in helium has been measured along the magnetic field with the following results: Single peaks of radiation were observed at the harmonic frequencies which slowly decreased in amplitude with increasing harmonic number; these peaks were almost completely circularly polarized with a polarization opposite to that of the emission by an electron; a large peak was observed near the fundamental in the electron polarization only, harmonic emission appeared only in the presence of the hot electrons produced by electrons beam; the difference in the emissions of the two polarizations indicated that most of radiation in the electron polarization came from the end of the plasma and had a large absorption in the interior of the plasma while most of the opposite polarization containing the electron cyclotron harmonic emission came from the interior of the plasma and had a much smaller absorption through the plasma. A theory proposed by Persson, Johnson, and Uhlenbrock showed detailed agreement with these measurements.
Numerical Evaluation of the Tietjens Function
Authors: Huppert Herbert E.
Published: February 2004

The Tietjens function is expressed in terms of two power series, which are much simpler and take significantly less time to calculate than those recently proposed by Chen, Joseph, and Sparrow.
Singularities of the Fluid Equations and Their Relation to Anomalous Diffusion
Authors: Friedman Herbert W. , Levi Enrico
Published: February 2004

The nonlinear equations governing the diffusion of magnetized plasmas do not admit steady-state solutions when the magnetic field intensity exceeds a critical value. This may explain the onset of instabilities leading to anomalous diffusion.
Motion of Charged Particles in Growing or Decaying Circularly Polarized Waves
Authors: Sonnerup B. U. Ö.
Published: February 2004

A constant of motion is derived for a charged particle in the magnetic and electric fields of a circularly polarized wave with time-variable amplitude. The wave is assumed to propagate along a uniform external magnetic field.
Ion Density and Electric-Field Perturbations Caused by an Acoustic-Wave Pulse in a Weakly Ionized Gas
Authors: Ingard Uno , Schulz Michael
Published: February 2004

A weak shock wave in a weakly ionized gas is shown to produce ion density and electric-field perturbations with shock “widths” approximately equal to (Te/Tn)l, where l is the mean free path in the neutral gas and (Te/Tn) is the electron-to-neutral-gas temperature ratio.
Intense Explosions at the Ocean Surface
Authors: Collins Richard , Holt Maurice
Published: February 2004

An approximate solution to the problem of an intense point-source explosion at the interface separating two different fluids is described; in particular, it is applied to a nuclear explosion initiated on the surface of the ocean. Of special interest is the position of the deformed ocean surface as a function of time during the initial phase of the explosion. The equations of motion for an inviscid fluid with no heat conductivity are written in terms of the verticle angle and a similarity variable. The solution is valid for the early phase of the explosion, during which the counterpressure remains insignificant. It is found that the influence of the free surface on the vacuum interface propagated in the water is confined to a 45° sector adjacent to the original free surface. Below this, the vacuum surface retains very nearly its spherical form. This picture of the flow-field form is seen to be in good qualitative agreement with the type of flow fields calculated by Brode and Bjork for a megaton burst on the surface of the earth.
Vapor Condensation in a Shock Tube—Electrostatic Effects
Authors: Grosse Fred A. , Smith Wesley R.
Published: February 2004

Shock waves propagating through sec-butyl alcohol and carbon tetrachloride vapor produce condensation of the vapor molecules on the shock-tube walls in the form of a thin liquid film. Electrostatic voltage changes in the potential of narrow metal foils wrapped around the outside of a glass shock-tube section are associated with the passage of the shock wave through the vapor. The electrostatic signals have been attributed to the shear at, or in the liquid film, due to the presence of the laminar vapor boundary layer established by the shock. The observed signals are consistent with a cylindrical sheet of positive charge which originates at the shock and extends behind the shock for a length equal to that of the laminar boundary layer.
Establishment of Steady Hydromagnetic Flow past Slender Bodies
Authors: Fan D. N. , Ludford G. S. S.
Published: February 2004

Fan's treatment [Phys. Fluids 10, 1756 (1967)] of the plane flow of a moderately good conductor is here extended to the more realistic axially symmetric case, for two reasons: to substantiate the algebraic decay of the transient motion; and to clear up an apparent contradiction which would have invalidated the perturbation analysis used in both. The magnetic field diffuses in from a solenoid wound round the circular tunnel in which potential flow past the slender body has been set up. The ultimate flow is found to be essentially Lary's steady motion when the tunnel is very wide, thus substantiating the practical relevance of his work.
Influence of Secondary Electrons on an Electron-Beam Probe
Authors: Harbour P. J. , Bienkowski G. K. , Smith R. B.
Published: February 2004

The flow of secondary electrons, produced by ionization when an electron beam traverses a gas, is retarded by electrostatic fields and their density is higher than has previously been assumed. An experiment indicates that low energy electrons could have important effects on an electron-beam density and temperature probe and that further research is needed.
Subcritical Instability and Exchange of Stability in a Horizontal Fluid Layer
Authors: Joseph D. D. , Goldstein R. J. , Graham D. J.
Published: February 2004

Rayleigh numbers calculated from linear and energy theories do not coincide when internal heat sources are present. For free boundaries exchange of stability applies, but energy theory nonetheless deems possible the existence of subcritical instabilities.
Impossibility of Steady Dynamos with Certain Symmetries
Authors: Lortz D.
Published: February 2004

It is shown that two-dimensional or axisymmetric steady electromagnetic fields cannot be generated by a continuous velocity field of any kind, even if the electric conductivity is a function of position.
Radial Profile of the Perturbation Density for the Helical Instability in a Positive Column
Authors: Reynolds J. F. , Jennings W. C. , Gunshor R. L.
Published: February 2004

An experimental investigation is made of the perturbation density at the onset of the helical instability in a positive column. Close agreement is found with the theoretical form assumed by Kadomtsev and Nedospasov.
Microwave Burst at Triggered Instability in a Hot Electron Plasma
Authors: Ikegami H. , Ikezi H. , Hosokawa M. , Takayama K. , Tanaka S.
Published: February 2004

A hot electron plasma is produced in a magnetic-mirror field by high-power microwave discharges. When an instability is triggered in a hot electron plasma, it is observed that the instability is accompanied by a burst of energetic electrons escaping from the magnetic mirror, a fast rising x-ray signal, a sudden increase of light intensity, and an intense burst of microwaves composed of harmonics of 2.1 GHz. This frequency cannot be explained in terms of the electron cyclotron frequencies associated with the magnetic field intensity within the plasma chamber.
Absorption in a Hot Plasma near the Second Harmonic of the Electron Cyclotron Frequency
Authors: Arunasalam V. , Meservey E. B. , Gurnee M. N. , Davidson R. C.
Published: February 2004

Analysis is presented of 4-mm microwave propagation in the extraordinary mode (for propagation angles of 76°, 90°, and 104° to the external magnetic field), near the second harmonic of the electron cyclotron frequency, across reasonably uniform, highly ionized cylindrical plasma columns (approximately 3, 4, and 5 in. in diameter) confined in a homogeneous (0.05%) magnetic field in the Model C stellarator. Reasonably good agreement with the general predictions of the conventional collisionless hot-plasma theory is obtained. In particular, the measured values of the width, the depth, and the strength of the experimentally detected absorption resonances fall within ±50% of the corresponding theoretically expected values. For these experiments the electron densities are typically in the range of 1011 to 1013 per cm3; the electron temperatures are in the range of 5-35 eV; and the electron collision frequencies ν are such that ν/ω ≲ 5 × 10−5, where ω is the angular frequency of the incident microwave beam.
Shock-Wave Structure in the Weakly Ionized Plasma
Authors: Muraoka Katsunori , Ikui Takefumi
Published: February 2004

The problem of the shock-wave structure in weakly ionized plasma is treated from the viewpoint of Mott-Smith approach, the result being compared with the previously obtained experimental data and with the solution using Navier-Stokes equation.
Spectrum of Density Fluctuations in Gases
Authors: Sugawara Akira , Yip Sidney , Sirovich Lawrence
Published: February 2004

The spectrum of density fluctuations in a simple gas is calculated by solving the linearized Boltzmann equation as an initial-value problem. The analysis is based on the method of polynomial expansion and on the use of generalized kinetic models. The numerical convergence of both types of solutions is studied, and it is shown that the method of kinetic models is capable of giving very accurate solutions to the Boltzmann equation at any wavelength to mean-free-path ratio. Explicit results are obtained for two repulsive interactions, the rigid-sphere potential and the Maxwell molecule potential. It is found that density fluctuations are not very sensitive to the details of the repulsive part of the intermolecular interaction.
Small-Scale Structure of a Scalar Field Convected by Turbulence
Authors: Kraichnan Robert H.
Published: February 2004

Batchelor's theory of the turbulent straining of small-spatial-scale amplitude variations of a convected scalar field is re-examined to see the effects of fluctuation of the rates of strain in space and time. The k−1 viscous-convective-range spectrum is unaltered, except for the constant of proportionality, but spectrum level in the viscous-diffusive range displays a sensitivity to fluctuations which increases with wavenumber. The Gaussian cutoff found by Batchelor is replaced by more gently decreasing dependences of spectrum level on wavenumber. The scalar spectrum is also treated by the Lagrangian-history direct-interaction approximation. The k−5/3 inertial-convective range of Obukhov and Corrsin, the k−1 viscous-convective range, and the k−17/3 inertial-diffusive range of Batchelor, Howells, and Townsend all are recovered. For a given rate of spectral transport of scalar variance, the predicted spectrum levels in the k−5/3 and k−1 ranges are too small, in comparison with experiment, by numerical factors in the neighborhood of one to three. The largest error is for the k−1 range at large Reynolds number.
High-Temperature Thermal Conductivity of Argon
Authors: Fay James A. , Arnoldi Douglas
Published: February 2004

Measurement of shock-tube end-wall heat transfer shows a secular change at long time which is ascribed to variation of gauge thermal conductivity with depth.
Current Sheet Dynamics in an Inverse Pinch Shock Tube
Authors: Sorrell F. Y.
Published: February 2004

Experiments were performed in argon, helium, and hydrogen in an inverse pinch electromagnetic shock tube. The current sheet and shock wave trajectories were measured by using magnetic pickup coils and piezoelectric pressure probes, respectively, and the electron number density was determined from electrostatic probes and by using the Stark broadening effect on spectral lines. The experimental parameters vary from conditions where the dominant heating mechanism in Ohmic dissipation to those where shock heating is greater. Snowplow speed for the current sheet is measured in all cases and low levels of ionization within the sheet were observed for the conditions where Ohmic dissipation was the only heating mechanism. A description of how a current sheet with a low degree of ionization can sweep up the gas it encounters (snowplow) is given.
Numerical Solution of Plasma Wave Equation for a Linear Confining Potential
Authors: Horton C. W.
Published: February 2004

The linearized Vlasov and Poisson equations governing electron plasma oscillations are solved numerically for the case of a Maxwellian electron gas confined by a linear potential. An iterative method of solving the wave equation is developed using a local Fourier transform to demonstrate convergence of the method. The numerical solution verifies and extends the results obtained analytically with the WKB theory by Berk, Horton, Rosenbluth, and Sudan. The reflection coefficient obtained from the numerical solution is compared with the first-order WKB reflection coefficient. The numerical calculation demonstrates that the higher-order reflection processes are smaller than the first-order process.
Scattering of Supraluminous Plasma Waves by Inhomogeneities
Authors: Lerche I.
Published: February 2004

The far-field electromagnetic radiation produced when a field of supraluminous longitudinal plasma oscillations is incident on a localized inhomogeneity in the thermal plasma density is calculated. The plasma is assumed collisionless and is composed of stationary ions and thermal electrons. The calculation makes use of the thermal equilibrium spectrum of supraluminous waves (with phase velocities greater than the speed of light), which do not Landau damp. The generation and maintenance of this supraluminous spectrum is discussed elsewhere. Upon inserting numerical values for typical laboratory plasmas and also for a typical astrophysical radio source, such as the Crab nebula, it is demonstrated that the phenomenon is completely negligible in the laboratory but can be important in astrophysical systems.
Spherical-Harmonic and Power-Series Expansion of the Boltzmann Equation
Authors: Morrone Terry
Published: February 2004

The spherical-harmonic expansion of the Boltzmann equation is expanded in a power series in a small parameter, the average fraction of energy an electron loses per collision. The power-series expansion permits an ordering in magnitude of the expansion coefficients of the distribution function, and thus indicates that many terms in the equations relating to the coefficients may be neglected.
Numerical Experiments on a Model System for Magnetohydrodynamic Turbulence
Authors: Thomas John H.
Published: February 2004

A one-dimensional system of equations modeling the incompressible magnetohydrodynamic equations is proposed. Numerical experiments corresponding to the “turbulent dynamo” problem, in the form of a statistical initial-value problem for the model system, are performed. Correlations, energy spectra, and other properties are examined at various times. The advantage of the model system is that no approximation need be made for the nonlinear “transfer” terms whose balance controls the outcome. The results of the experiments are that, for Reynolds number R in the range 4-20, dynamo action occurs in the model system whenever the magnetic Reynolds number Rm is greater than or equal to R. Dynamo action also occurs in the case R = 20, Rm = 4, but fails to occur for R = 20, Rm = 0.2. In all cases where dynamo action occurs, the magnetic energy approaches the equipartition level, sometimes after first overshooting this level by a considerable amount.
Structure of Turbulence in a Curved Mixing Layer
Authors: Wyngaard J. C. , Tennekes H. , Lumley J. L. , Margolis D. P.
Published: February 2004

Earlier conclusions about the nature of the turbulent energy budgets, the value of the inertial subrange spectral constant α, and the turbulence Reynolds number Rλ in a curved mixing layer are revised in view of the results of a recent investigation.
Onset of Convection in a Layer of Water Formed by Melting Ice from Below
Authors: Yen Yin-Chao
Published: February 2004

The onset of convection, or the critical Rayleigh number in a layer of water formed continuously by melting ice from below, has been determined experimentally. Homogeneous, bubble-free ice was prepared, and used in all the experiments. The critical Rayleigh number Rac for a fluid undergoing phase change and density inversion is not a single value but may be correlated empirically as a function of warm plate temperature T8 by Rac = 14 200 exp (−6.64 × 10−2T8). This relation is valid for T8 varying from 6.72-25.50°C. The initial ice sample temperature T0 was varied from −4.8 to −22.00°C. The effect of T0 was found to be insignificant.
Boundary-Layer Flow on a Vertical Plate
Authors: Ackerberg Robert C.
Published: February 2004

The motion of a film of viscous incompressible fluid running down a semi-infinite vertical plate under the influence of gravity is considered. The problem is to determine how the final asymptotic shear flow is achieved when the fluid is introduced at the leading edge with uniform velocity. The Reynolds number Re and the Froude number Fr, based on the initial film thickness and velocity, characterize the flow and are assumed large compared to unity. For these cases the motion is determined uniformly to first order by solutions of the boundary-layer equations in terms of a single parameter ε = (Fr/Re)12 which is assumed small. Numerical solutions of the boundary-layer equations are obtained using Mises variables for 0 ≤ ε ≤ 0.5. The results indicate that all solutions, for sufficiently small ε, become indistinguishable (in terms of scaled variables) from the solution obtained for ε ≡ 0 after a short distance downstream, and this occurs before the potential flow has been absorbed by the boundary layer. This “forgetfulness” of the initial conditions is found to be associated with a nonuniform limit at the leading edge when ε → 0.
Rarefied-Gas Flow in the Knudsen Layer
Authors: Reddy K. C.
Published: February 2004

Discrete ordinate method has been applied to the Bhatnagar-Gross-Krook model to analyze the velocity field in the Knudsen layer. An exact relation between the macroscopic velocity at the plate and the shear stress has been obtained. The method also provides accurate numerical results for quantities of interest such as slip coefficient. Another method of solution using a transform technique is also indicated.
Thermal Escape Problem. II. Transition Domain in Spherical Geometry
Authors: Ziering Sigi , Hu Pung Nien , Sheinblatt Marshall
Published: February 2004

Previous analysis of the problem of thermal escape from planetary atmospheres by kinetic theory techniques is extended. The two restrictions previously used of (a) plane layer approximation, and (b) constant gravitational field within a scale height, are removed in order to make the problem physically more meaningful. The distribution functions, chosen for the transition domain, are consistent with the continuum type of distribution expected to dominate at the lower boundary. At the same time a discontinuity (at the escape speed) is built into the distribution functions, to allow for a microscopic incorporation of the boundary conditions at the upper boundary where the transition zone merges with the free flow domain. A simplified collision term of the BGK type is used, and the constant collision term in the model is adjusted so as to yield the exact diffusive flow in the collision dominated regime, which is the expected driving mechanism for thermal escape. A two-component solution yielding analytic results is obtained by only allowing a spatial variation of the respective densities. The full four-component solution can be shown to be reducible to two coupled first-order differential equations with variable coefficients, and an expansion method of solution has been established else-where. The well-known barometric decay constant found in elementary solutions is shown to be a partial solution present in both the two-component and the four-component approximations.
Lateral Instability of a Stream of Charged Droplets
Authors: Crowley Joseph M.
Published: February 2004

Transverse displacements of a stream of charged droplets are unstable due to electrostatic repulsion. The instability is most pronounced at the shortest wavelength physically possible on the stream.
Comparison of a Two-Dimensional Snowplough Model with Experiment
Authors: Basque G. , Jolas A. , Watteau J. P.
Published: February 2004

The current sheath dynamics deduced from a two-dimensional axisymmetric snowplough model fits well with what is photographically observed on a noncylindrical Z-pinch experiment. Relative agreement is found between computed and measured electrical quantities.
Flow of a Rarefied Gas past an Axisymmetric Body. I. General Remarks
Authors: Cercignani C. , Pagani C. D.
Published: February 2004

A general variational principle used to solve various problems in kinetic theory, is now applied to the problem of the flow past an axisymmetric body. It is shown that the drag exerted by the flow on the body is closely related to the stationary value of a given functional.
Stability of Pipe Poiseuille Flow
Authors: Lessen Martin , Sadler Stanley G. , Liu Ting-Yung
Published: February 2004

The stability of pipe Poiseuille flow with respect to linear azimuthally periodic disturbances is investigated. It is found that many radial modes of disturbance exist for each azimuthal periodicity. No linear instability is found for the mode sets with azimuthal periodicity of one.
Oscillating Convection in an Elasticoviscous Liquid
Authors: Green Theodore
Published: February 2004

In the presence of a large restoring force, an oscillating convective motion is possible in a thin layer of an elasticoviscous liquid.
Upstream Influence in Viscous Interaction Problems
Authors: Garvine Richard W.
Published: February 2004

A study of hypersonic viscous interaction on a flat plate is presented. It is shown that the numerical solutions develop singular behavior with respect to the initial data employed. Nonsingular solutions are possible only when a parameter in the initial data is fixed at some specific value which is not known a priori. The origin of this singular dependence is then investigated. It is found that the problem is improperly set as an initial value problem because the interaction dynamics contain upstream influence. If the problem is attacked as an initial value problem, then a constraint must be placed on the initial flow profiles if a bounded solution is to result. Finally, an approximate numerical method is presented to develop this nonsingular solution for the original system of coupled nonlinear equations.
Analysis of Confined Magnetohydrodynamic Vortex Flows
Authors: Loper David E. , Ostrach Simon
Published: February 2004

The vortex flow of a viscous, incompressible, and electrically conducting fluid confined between two finite flat plates (with a net radial mass flow) in the presence of an applied axial magnetic field is considered. The details of the velocity field including boundary-layer thickness and redistribution of radial mass flow are of primary concern. The analysis is limited to the case of the separation distance between the two end plates being small compared with the radius of the plates; this allows the momentum equations to be uncoupled from the electromagnetic equations. The momentum equations are linearized and solved for the velocities and the pressure as Fourier series. It is found that magnetic effects tend to decrease the boundary-layer thickness by a small percentage and tend to decrease substantially the mass flow drawn into the boundary layers.
Validity of the Classical Detonation Wave Structure for Condensed Explosives
Authors: Petrone Francis J.
Published: February 2004

A series of numerical computations has been carried out to obtain an accurate solution to the flow resulting from a detonating charge in contact with metal plates of various thicknesses in order to (i) determine the validity of the classical model for the detonation structure of condensed phase explosives, (ii) determine any effect of the complex wave interactions of the reflected waves within the reaction zone on the measured free-surface velocities of the shocked metal, and (iii) remove the anomaly of the previously observed “decay” zone. The present investigation leads to a new interpretation of free-surface velocity measurements for thin plates, which supports the classical theory of the detonation wave structure for condensed media and results in experimental values of the Chapman-Jouguet parameters which are in consistent agreement with both the “theoretically” predicted Chapman-Jouguet values and the directly measured (by the electromagnetic method) Chapman-Jouguet values.
Theory and Measurements for Ion Collection by a Spherical Probe in a Collisional Plasma
Authors: Self S. A. , Shih C. H.
Published: February 2004

Following a discussion of existing probe theories for a collisional plasma, a new theory is given for ion collection by a spherical probe in a collisional plasma which goes over to the collisionless theory of Allen et al. at low pressures and the continuum theory of Su and Lam at high pressures. Numerical results are given in a form suitable for interpretation of experimental data. Experimental probe studies in the positive column (1 cm diameter) of a He discharge in the pressure range 0.05-0.4 Torr are described and the use of the electron and ion saturation methods for determining plasma concentration compared with one another and with a microwave cavity perturbation method. The limitations of the theories and experimental methods are discussed.
Magnetic Shielding of Current Feeds in Plasma Containment Systems
Authors: Burkhardt L. C. , DiMarco J. N. , Hammel J. E. , Henson R. M. , Karr H. J.
Published: February 2004

Experimental tests of the effectiveness of the magnetic shielding of current leads or supports in the form of linear dipoles are described. Results show that this technique may be useful in experimental plasma confinement devices.
Measurement of Electron Temperature Using Relative Line Intensities of Argon ii
Authors: Kribel R. E.
Published: February 2004

The electron temperature in an argon magnetoplasmadynamic arc has been measured at 1.1 ± 0.3 eV. The magnitude of the transition probability for the 4847.9 ÅA line of A ii is much closer to the theoretical value than reported in earlier measurements.
Production and Propagation of Plasmoids in a Nonlinear Alfvén Wave
Authors: Wells Daniel R. , Norwood Joseph
Published: February 2004

A variational theory of hydromagnetic dynamic equilibria is applied to plasmoids produced in a conical theta pinch immersed in a magnetic guide field. The solutions correspond to nonlinear Alfvén waves which trap and transport plasma.
Stability of Rotating Couette Flow. II. Comparison with Numerical Results
Authors: Snyder H. A.
Published: February 2004

Measurements have been made of the onset of instability in rotating Couette flow in order to check some recent numerical results. The case of a very wide gap, a medium gap, and a very narrow clearance ratio have been studied. The accuracy of the results is about ± 2%. The present data and other values available in the literature are compared with the computations of different investigators. With a few exceptions the agreement is found to be excellent. End effects are described and their relative importance is discussed. Methods of scaling the results are evaluated. A simple formula is presented for calculating the onset value when only the inner cylinder rotates.
Diffusion Approximation for Turbulent Scalar Fields
Authors: Leith C. E.
Published: February 2004

A diffusion approximation is derived for the transfer of spectral components of mean-square fluctuations of a passive scalar quantity advected by an isotropic turbulent flow. This approximation, expected to be most useful for very large Reynolds numbers, preserves nonnegative spectral components and chaotic equilibrium solutions, as well as producing −53 power advection range spectra in appropriate circumstances. A comparison is made with some observations of Gibson and Schwarz at a Prandtl number of 7. Cutoff difficulties at large wavenumber make the approximation questionable for Prandtl numbers much greater than 7.
Stagnation Point Flow with Complex Composition
Authors: Libby Paul A. , Sepri Paavo
Published: February 2004

A previous study of the laminar boundary layer involving four inert species with widely different molecular weights but with a uniform external stream has been extended to describe such a boundary layer at an axisymmetric stagnation point. The transport properties of the gas mixture are described with reasonable accuracy so as to permit assessment of the importance thereof on the predictions of the boundary-layer behavior. Comparison of the exact calculations is made with the predictions based on the “cold wall” approximation and on a model based on the inner-layer solutions for “massive blowing.”
Self-Gravitational Instability of a Fluid Layer with Finite Resistivity
Authors: Sundaram A. K.
Published: February 2004

A study of the stability of a self-gravitating fluid of variable density with finite resistivity is described. A variational technique is established, and it is proved that the system cannot be overstable. It is also shown that the system is unstable for all wavenumbers and finite resistivity.
Second-Order Contributions to Transport Processes in a Plasma
Authors: Luks K. D. , Davis H. Ted
Published: February 2004

The second-order pressure tensor and heat-flux vector are obtained for a one-component plasma by applying the Chapman-Enskog method of solution to the Balescu-Guernsey-Lenard kinetic equation. To illustrate the temperatures and densities at which second-order effects may be important in plasmas, the hydrodynamic problem of Couette flow between flat plates is analyzed.
Nonlinear Effects of Large-Amplitude Plasma Waves
Authors: Wharton C. B. , Malmberg J. H. , O'Neil T. M.
Published: February 2004

The oscillations of resonant electrons in the potential of a large-amplitude, spatially propagating plasma wave result in: (1) periodic maxima in space of wave amplitude, (2) growth of sidebands on the transmitted frequency, and (3) periodic enhancement of the energy of the trapped electrons. Measurement of these effects is reported.
Effect of Incomplete Accommodation on Transition Regime Heat Transfer and Shear
Authors: Lord R. G.
Published: February 2004

A method is described of extending theories of heat transfer and shear between coaxial cylinders and concentric spheres to the case of arbitrary accommodation coefficients at both inner and other surfaces. Correction formulas for these problems are derived.
Radiative Energy Addition behind a Shock Wave
Authors: Rehm Ronald G.
Published: February 2004

Monochromatic radiation propagating in a direction opposite to that of a uniform, one-dimensional shock wave is absorbed throughout the region behind the shock front. Euler's equations for unsteady flow with energy addition and the macroscopic equation for radiative transfer neglecting emission are used to describe the motion. Behind the shock front it is assumed that the energy added to a fluid element during heating is small compared with its initial internal energy. Then, the mathematical method of strained coordinates (Poincaré-Lighthill-Kuo technique) can be applied, and it is found that the radiation is exponentially attenuated behind the shock wave. The absorbed radiation accelerates the shock wave and generates a secondary shock front. The time at which the secondary shock wave appears is inversely proportional to both the intensity of the radiation and the absorption coefficient. The asymptotic constant velocity of the secondary shock wave is found to equal the speed of a rearward propagating acoustic wave plus a correction proportional to the radiation intensity.
Polar Fluids
Authors: Cowin S. C.
Published: February 2004

It is noted that a number of theories proposed recently by various authors are actually identical with the theory of polar fluids suggested by Grad in 1952. The relatively close relationship of the recently presented theory of dipolar fluids to polar fluid theory is established. The thermodynamics of polar fluids with heat conduction is sketched. The solved boundary-value problems of polar fluid theory are summarized and the essential features of these solutions establish a pattern that gives insight into the behavior of polar fluids as well as indicating where the theory might be of practical significance.
Kinetic Theory of Sound for a Polyatomic Gas
Authors: Ninham B. W. , Wood W. P.
Published: February 2004

The initial-value problem is studied for an unbounded gas whose molecules possess internal energy states. A relaxation model is used to approximate the Wang Chang-Uhlenbeck generalization of the Boltzmann collision integral for a polyatomic gas. The model depends on two adjustable parameters, the elastic and inelastic relaxation times. The problem gives some insight into the behavior of the collective modes of motion of the gas. For linear molecules permitted rotational but not vibrational degrees of freedom the model predicts corrections to the adiabatic sound velocity of (7kT/5m)12 in the near continuum limit. The absorption as well as purely dissipative modes are obtained as functions of the elastic and inelastic relaxation times.
Turbulent Diffusion, Particle Orbits, and Field Fluctuations in a Plasma in a Magnetic Field
Authors: Weinstock Jerome
Published: February 2004

A universal relationship is deduced between diffusion coefficients, electric field spectra, and averaged Liouville orbit functions for a turbulent plasma in a magnetic field. This relation is a generalization of a similar relation previously derived by Dupree from completely different considerations. In particular, the solution of the Vlasov equation is avoided. Aside from generality and rigor, the present result differs from Dupree's in that the latter involves Vlasov orbit functions whereas the former involves Liouville orbit functions. The Liouville orbit function is easily evaluated by expanding in terms of the cumulants (semi-invariants) of the moments of the exact particle orbits. Dupree's results are thus produced without having to solve the nonlinear Vlasov equation. The present results can be viewed as an extension of Spitzer's diffusion formula to strong plasma turbulence. Conditions for the validity of the diffusion expression are determined, and corrections are made for mode frequencies in excess of gyro-frequencies.
Numerical Experiment on Ion Cyclotron Heating
Authors: Hasegawa Akira , Kamimura Tetsuo
Published: February 2004

A numerical experiment with a sheet current model is performed to study nonlinear phenomena related to ion cyclotron heating. The model has successfully reproduced damping of ion cyclotron waves at the magnetic beach and consequent heating of ions. Results of the experiment show that the plasma particles are scattered at the beach in the process of the heating. It is also seen that the perpendicular ion temperature increases first and the parallel ion temperture increases some time later.
Unstable, Transverse-Displacement Mode of a Bumpy Plasma Column and Its Possible Stabilization
Authors: Ribe F. L. , Riesenfeld W. B.
Published: February 2004

Extension of considerations of high-β toroidal equilibria allows calculation of the destabilizing m = 1 force on a straight axisymmetric, bumpy plasma column. The modification of the bumpy equilibrium by a weak longitudinal current is determined. The m = 1 mode becomes helical and can be stabilized when the current is oscillated.
Nonlinear Effects of Propagating Extraordinary Waves in a Cold Plasma
Authors: Das K. P.
Published: February 2004

The perturbation method of Bogoliubov, Krylov, and Mitropolsky is applied to the study of nonlinear effects of propagating waves of extraordinary mode in a cold plasma. Amplitude-dependent wavelength and frequency shifts including relativistic corrections are obtained.
Electromechanical Stream-Structure Instabilities
Authors: Ketterer Frederick D. , Melcher James R.
Published: February 2004

The dynamics of a highly conducting fluid stream coupled by means of a transverse electric or parallel magnetic field to a conducting elastic medium is examined in detail. From the dispersion relation and the Bers-Briggs criterion, the stability of the infinite length system is described. Eigen-frequencies and eigenfunctions are computed for the finite length system and good agreement is obtained with an electrohydrodynamic experiment. A physical explanation is given for the overstabilities observed. The close analogy between a limiting case of the field-coupled system and an electron beam coupled to a traveling wave structure is discussed.