bluuebunny/crossref_metadata_2025 huggingface dataset:
Faraday Rotation Measurements on the Scylla IV Theta Pinch
Authors: Gribble R. F. , Little E. M. , Morse R. L. , Quinn W. E.
Published: February 2004

Faraday rotation measurements have been combined with Mach-Zehnder interferometer measurements to yield the value of the internal magnetic field Bi in the Scylla IV plasma as a function of time and radius. Since the Faraday rotation is proportional to ∫ Bi(l)ne(l) dl and the Mach-Zehnder interferometer provides ∫ ne(l) dl, the data give the average value of the internal magnetic field Bi(r) which exists over the plasma length l at the radius r. The measurements of Bi(r) are combined with those of the external magnetic field Be to determine the average plasma β as a function of radius, β = 1 − Bi2(r)/Be2. The Faraday rotation measurement employs a 1.5-mm diam beam of visible radiation (6328 Å) from a He-Ne gas laser as a plasma magnetic-field probe and a calcite Wollaston prism as the polarization analyzer with silicon diode detectors. In the low-pressure plasma regime (10-25 mTorr) the β values in the central plasma-core (∼5-mm diameter) range in value between 0.9 and 1.0 with initial reversed bias magnetic fields and between 0.7 and 0.95 without bias fields. Radial profiles of β averaged over the plasma length have been obtained at various times during the discharge. A combination of β, n, and Te in the simple pressure balance yields ion temperatures in the 2- 6-keV region.
Acceleration of Plasma by a Propagating Current Sheet
Authors: Burton Rodney L. , Jahn Robert G.
Published: February 2004

The structure of a propagating current sheet in a linear pinch discharge in argon is examined with magnetic and electric probes, and interpreted from a magnetogasdynamic point of view. From an integration of the jzBθ distributions it is deduced that the bulk of the initial mass fill of the chamber is radially accelerated to the current sheet velocity. Acceleration of ions in the sheet is partially accomplished by a radial electric field, which imparts about half of the necessary energy. The remaining energy is acquired through a jz+Bθ force applied to the ions, which are deflected axially as they pass through the sheet, and, therefore, conduct a large fraction of the axial current.
Resistive Instabilities of a Viscous Fluid with Horizontal Boundary
Authors: Zadoff Leon N. , Begun Martin
Published: February 2004

The gravitational instabilities of a system consisting of two homogeneous fluids with horizontal interface, in the presence of a uniform horizontal magnetic field, are investigated. The fluids are incompressible and have finite electrical conductivity and viscosity. The dispersion relation, which is obtained for the general case, is then specialized for a lower fluid of vanishing density, viscosity, and conductivity. In the limit of infinite conductivity in the upper fluid, the resulting dispersion relation corresponds to that previously obtained for a conducting fluid supported by a magnetic field against gravity. For finite conductivity in the upper fluid, this procedure avoids the difficulties involved as a result of diffusion across a supporting magnetic field. The effects of viscosity and resistivity on the Rayleigh-Taylor modes are obtained. In addition, a resistive gravitational interchange instability is found, although magnetic shear is absent. It is further established that a small viscosity diminishes the growth rate of the resistive gravitational instability.
Examination of Numerically Calculated Heat Fluxes for Evidence of a Supercritical Transition
Authors: Deardorff J. W.
Published: February 2004

Numerical integrations of two-dimensional convection between rigid horizontal boundaries performed by the author and others for small Rayleigh numbers, for a Prandtl number of unity, and for a fundamental wavelength of twice the height, are examined closely to see if they reproduce the experimental result that NR = aR − b, where N is the Nusselt number and R the Rayleigh number. If only one mode of convection were present, this linear law would be obeyed. The presence of higher modes in the calculations causes NR to gradually increase faster than the linear law as R increases. It is concluded that the discrete transitions of Malkus are not associated with instability of higher vertical modes when the convection is forced to be two dimensional with a fixed maximum horizontal wavelength.
Effect of Boundary Conditions on the Onset of Convection
Authors: Foster Theodore D.
Published: February 2004

The effect of various boundary conditions on the onset of convection in a semi-infinite fluid which has a time-dependent temperature profile is investigated. The linearized hydrodynamic and thermodynamic equations are solved by expanding the variables in a series of orthonormal functions satisfying the boundary conditions and integrating the resulting set of coupled ordinary differential equations numerically. For a semi-infinite fluid the initial behavior of the system is found to depend mainly on the Prandtl number and the manner in which the fluid is cooled or heated. The various combinations of rigid, free, conducting, and insulating boundary conditions only slightly affect the time of onset of manifest convective behavior and the horizontal wavenumber of the disturbances which are amplified the most at this time.
Laminar Boundary Layer with Mass Transfer and Slip
Authors: Wazzan Ahmed R. , Lind Richard C. , Liu C. Y.
Published: February 2004

A method is developed to solve the two-dimensional incompressible laminar boundary layer with mass transfer and slip at the surface. The properties of the injected gas are assumed the same as those of the main flow. The velocity distribution is nonsimilar in the flow direction and is obtained by a series expansion in terms of a mass transfer parameter ε(S) and a slip parameter σ(S). Results are presented for various combinations of the two parameters. The validity of the method is verified by comparison with a momentum integral type solution over a range of values of the two parameters.
Kinetic Description of Cylindrical Heat Conduction in a Polyatomic Gas
Authors: Cipolla J. W. , Morse T. F.
Published: February 2004

A kinetic description has been obtained for a polyatomic gas between concentric cylinders maintained at different temperatures. Knudsen iteration on a polyatomic kinetic model equation has been employed to obtain first collision corrections to the free molecular distribution function. It is assumed that the temperature difference between the cylinders is small. The heat transfer vector obtained from this theory has been compared with the results of Lees' moment method to obtain an estimate of the range of Knudsen number for which the theory should be valid.
Equilibration of a Uniform Two-Temperature Mixture of Maxwell Molecules
Authors: Jhunjhunwala Nandlal , Mintzer David
Published: February 2004

A mixture of two Maxwell molecule gases having different temperatures, but uniformly distributed in space is considered. The exact equations for the second- and fourth-order moments are developed; no truncation is necessary for this problem. The temperatures of the two species are readily found. The fourth-order moment equations are solved, with details given for the cases of identical molecules, and of large molecular mass ratio. The coefficients in generalized orthogonal polynomial expansions are then found in terms of the moments; the zero-order distributions used are Maxwellian with the initial gas temperatures, the final temperature, or the time-dependent temperature. The meaning for the various forms for the coefficients is discussed; it is shown that only in the case of large mass-ratio gas mixtures does a Maxwell distribution always remain Maxwellian.
Experimental Study of Rarefied Argon Contained between Concentric Cylinders
Authors: Sheldon Duncan B. , Springer George S.
Published: February 2004

Measurements were made in rarefied stationary argon contained between vertical concentric cylinders, with a fine wire probe aligned parallel to the axis of the cylinders. At different radial positions an equilibrium probe temperature was determined by measuring the temperature of the probe when there was no net energy exchange between the probe and the surrounding gas. When the center cylinder was in the transition regime (0.15 < Knc < 5), the experimental equilibrium probe temperatures were compared to equilibrium probe temperatures calculated using the moment method of Lees and Liu together with the assumptions that (a) the probe was in the free molecule regime, (b) the gas-surface interaction at the probe could be described by Knudsen's thermal accommodation coefficient, and (c) the thermal accommodation coefficients at the probe and at the cylindrical surfaces remained constant. For Knc > 0.5 agreement between the experimental and calculated equilibrium probe temperatures was within ∼2.5%. Equilibrium probe temperatures were also compared to local gas temperatures calculated by Smoluchowski's temperature jump approximation, and for Knc < 0.15 agreement was found to be within ∼1%. In the range 0.15 < Knc < 0.5 the results of both the moment method and the temperature jump approximation deviated (in opposite directions) from the data by a maximum of 4%.
Nonlinear Rarefied Couette Flow with Heat Transfer
Authors: Huang A. B. , Hartley D. L.
Published: February 2004

In order to calibrate the new, general discrete ordinate method proposed by Huang against the known standard solutions, the proposed method is applied to the problem of nonlinear Couette flow with heat transfer whose numerically exact solutions are available. It is shown that the proposed method yields excellent results over a large range of Knudsen numbers (from free molecular to near-continuum flow regime). In contrast to other methods, an important advantage of the proposed method is the calculation of the local molecular velocity distribution function which is useful in the direct comparison with molecular beam experimental results.
Asymptotic Integral Property of a Diffusion-Recombination Equation
Authors: Sherman Christopher
Published: February 2004

The total number of particles which remain unrecombined in a system of charged particles undergoing simultaneous diffusion and recombination is calculated numerically. The results of this calculation as well as of heuristic arguments indicate that the asymptotic limit of total unrecombined particles as the time becomes infinite is zero for a planar or cylindrical space but is not zero for a spherical space.
Example of an Isothermal Shock Wave
Authors: Thomsen John S.
Published: February 2004

It is shown that an isothermal shock wave can occur in liquid water just below its temperature of maximum density. Thermodynamic functions previously obtained by Thomsen and Hartka are used to obtain an explicit solution of the Hugoniot relation under isothermal conditions; the resulting entropy increase is also computed. Such a shock takes place between a state in the anomalous region (negative coefficient of thermal expansion) and one in the normal region (positive coefficient). For the most part, properties of the shock wave are similar to the usual cases; certain anomalies are briefly discussed. The results apply qualitatively to any other fluids with similar properties, if such exist.
Effects of Chemical Kinetics on Near Equilibrium Combustion in Nonpremixed Systems
Authors: Kassoy David R. , Williams Forman A.
Published: February 2004

The method of matched asymptotic expansions is employed for a systematic analysis of some chemical kinetic effects on near equilibrium combustion of nonpremixed systems. The model problem of a spherically symmetrical liquid fuel droplet in an oxidizing enviroment is chosen as a vehicle of study because it leads to relatively concise analytical solutions. As a consequence of the choice of a one-step irreversible finite-rate Arrhenius reaction, it is shown that perturbations from the equilibrium (infinite-rate reaction) mass burning rate and perturbations from the equilibrium temperature and composition profiles are affected functionally by the choice of reaction orders with respect to oxidizer and fuel. Pressure dependences of burning-rate perturbations are derived.
Steady-State Analysis of Quasi-One-Dimensional Reactive Flow
Authors: Erpenbeck Jerome J.
Published: February 2004

Steady quasi-one-dimensional flow is investigated for a general multi-reaction system, for an arbitrary equation of state satisfying the Bethe-Weyl conditions, and for a general class of lateral-expansion specifications. The nature of the various solutions is investigated, particularly with reference to the approach to chemical equilibrium and to transonic flow, with a view toward establishing a correspondence between a downstream boundary condition, whether for a nozzle problem or a detonation, and various types of integral curve behavior. The question of unsupported detonation structure and the quasi-one-dimensional Chapman-Jouguet condition is discussed and judged to be analogous to the one-dimensional detonation problem. The frequently quoted Chapman-Jouguet condition based on a special non-equilibrium condition at a frozen-sonic point is obtained only as a special case analogous to the “weak” one-dimensional Chapman-Jouguet condition. The equilibrium Chapman-Jouguet condition based on equilibrium-sonic flow is suggested as the normal case.
Transfer of Turbulent Energy and Scalar Quantities at Large Wavenumbers
Authors: Pao Yih-Ho
Published: February 2004

Pao's continuous spectral cascading concept for transferring turbulent energy and passive scalar quantities at large wavenumbers is reformulated in a more formal way.
Forced Flow of a Rotating Viscous Liquid Subject to Internal Heating
Authors: Driessche P. van den
Published: February 2004

A boundary-value problem is formulated for a rotating liquid with parabolic temperature profile which is heated from below. As rotation increases the magnitudes of radial and vertical velocity components decrease, zonal velocity first increases and then decreases.
Vibrational Energy Relaxation with Multiple Quantum Transitions
Authors: Northup L. L. , Hsu C. T.
Published: February 2004

By considering multiple quantum transitions for vibrational relaxation in a heat-bath problem, the Bethe–Teller relation still holds up to 7000°K for N2 gas, but the Landau–Teller plot exhibits nearly a straight line supporting recent experimental results.
Effect of Resonance Radiation on the Transfer of Shock-Precursor Radiation
Authors: Vulliet W. G.
Published: February 2004

Photo-ionization absorption of radiation frequencies that are much less than those of the ground state is possible when a cold, moderately dense gas is illuminated by a hot blackbody. A calculation is given for explosively shocked argon.
Guiding-Center Treatment of Finite Gyroradius Fluid Equations
Authors: Emmert G. , Schmidt G.
Published: February 2004

The finite gyroradius fluid equations of Rosenbluth and Simon are derived from guiding-center theory with finite gyroradius corrections. This derivation is simpler and physically more transparent than the original derivation.
Characteristics of Noise in a Two-Dimensional Computer Plasma
Authors: Hockney R. W.
Published: February 2004

The correlation time and root-mean-square value of the E-field fluctuations have been measured in a two-dimensional computer model of a plasma, thus enabling the collision and diffusion rates arising from computer errors to be predicted.
Magnetic Wells Produced by a Beam Current
Authors: Ohkawa Tihiro
Published: February 2004

The stability condition of interchange instability for plasmas confined in a magnetic well produced by beam current is discussed.
Space-Time Correlation Functions for the Enskog Dense Gas Theory
Authors: Gross E. P. , Wisnivesky D.
Published: February 2004

The Enskog kinetic equation for dense hard sphere gases is analyzed by separating the time reversible and time irreversible parts of the collision operator. The reversible part is responsible for the screening of a weak external potential. The short time behavior of the two-time density correlation function can be calculated or equivalently, the second- and fourth-frequency moments of its Fourier trans form. The Enskog predictions for the second moment agree with the exact microscopic result of de Gennes to the first power of the density. The disagreement for higher powers of the density can be traced to a fundamental defect of the Enskog collision frequency functional. The exact theory yields an infinite value for the fourth-frequency moment, in contrast to the finite value predicted by the Enskog equation.
Flow of a Rarefied Gas past an Axisymmetric Body. II. Case of a Sphere
Authors: Cercignani C. , Pagani C. D. , Bassanini P.
Published: February 2004

The drag exerted by the flow on a sphere is explicitly calculated by using the relation between the drag and a certain functional. A comparison of the results with the experimental data of Millikan gives excellent agreement.
Steady Gasdynamic Flows
Authors: Sirovich Lawrence
Published: February 2004

The steady Oseen equations for an arbitrary gas are considered. The inverse of the Oseen operator is obtained in closed form uniformly through transonic speeds in a certain limit. This limit is the same as the limit under which the Navier-Stokes equations are derivable from kinetic theory. The far field flow past an arbitrary body in terms of lift, drag, and energy dissipation of the body is obtained. As another application, the supersonic flow field past a semi-infinite flat plate is explicity obtained. The latter problem serves as the basis for an extension of the Oseen theory which gives an approximation of skin friction for arbitrary bodies.
Constitutive Equations for a Fluid Containing Nonrigid Structures
Authors: Kirwan A. D.
Published: February 2004

The general theory of structured fluids is discussed from a physical standpoint. Two new physical principles are utilized in developing constitutive equations. Restrictions on the phenomenological coefficients imposed by the second law of thermodynamics are obtained.
Stability of a Horizontal Fluid Interface in a Periodic Vertical Electric Field
Authors: Yih Chia-Shun
Published: February 2004

The stability of the interface in the presence of a periodic electric field is considered. It is shown that the stability is governed by a Mathieu equation, that the interface can be unstable even if the electric field is at all times weaker than that needed for instability in the case of a steady field, and that, when instability occurs, the waves may either be synchronous with the electric field, or have twice its frequency.
Shock Propagation in Spherically Symmetric Exponential Atmospheres
Authors: Lutzky M. , Lehto Delbert L.
Published: February 2004

Computer calculations have been made of the propagation of the shock from an explosion at the origin of a spherically symmetric, exponential, ideal-gas atmosphere. A generalization of Sachs scaling has been devised which allows a very convenient systematization of the pressure-distance curves, and which shows that, for a suitable normalization, these curves are straight lines throughout a significant range of yield, distance, and degree of atmospheric inhomogeneity. This technique is also used to investigate the validity of modified Sachs scaling, an approximate method of generating pressure-distance curves for an inhomogeneous atmosphere from the known results for a homogeneous atmosphere. It is found that modified Sachs scaling yields results which deviate from the hydrodynamic code calculations by at most 20% in the weak shock regime. This result is essentially independent of yield. Some comments are made on the applicability of these methods to the problem of shocks from explosions in horizontally stratified, real-gas atmospheres.
Experimental Investigations of Normal Ionizing Shock Waves
Authors: Levine Leslie S.
Published: February 2004

Experiments have been conducted on normal ionizing shock waves produced in a coaxial electromagnetic shock tube. Steady shock velocities were measured as a function of initial gas pressure, drive current, and applied axial magnetic field. The speeds agreed well with theoretical values. Measurements were made of the switch-on magnetic field, the upstream transverse electric field, and the density ratio across the front. The data all show that trans-Alfvénic shocks (uA l f1 < us ≲ 3uA l f1) exhibit Chapman-Jouguet behavior, with current flow in the shock front, and no separation of shock and drive currents. In contrast, super-Alfvénic shocks (us ≳ 3uA l f1) appear to be gas dynamic in nature. Spectroscopic measurements and shock-reflection studies demonstrated the presence of a nonluminous front and shock-heated gas preceding the luminous drive current.
Incident and Reflected Ionizing Shock Structure
Authors: Presby Herman M. , Meehan Richard J.
Published: February 2004

Separation of the electron density transition from the current sheet and the luminous peak has been observed with ionizing waves in an electromagnetic shock tube. Upon reflection of the shock, coalescing waves and macroscopic turbulence are seen.
Harmonic Generation from an Ionized Gas Slab
Authors: Vogel R. W. , Desloge E. A.
Published: February 2004

The effect of collisions on harmonic generation in an ionized gas slab through which an electromagnetic wave is passing is considered. The gas is assumed to be slightly ionized with electron-neutral molecule collisions dominating. An approximate distribution function is assumed which contains five undetermined parameters. Boltzmann's transport equation is used to obtain the appropriate kinetic equations governing the behavior of these parameters. The kinetic equations are coupled to Maxwell's equations and a Fourier solution in time is used. The ionized gas slab is stratified into a series of individually homogeneous laminae and the equations are solved. The first harmonic transmitted and third harmonic generated power are calculated and plotted versus input power for several collision cross sections.
Propagation of Circularly Polarized Electromagnetic Waves in a Finite Temperature Electromagnetoplasma
Authors: Hsieh H. C.
Published: February 2004

The dispersion relation for circularly polarized electromagnetic waves in a warm two-component plasma subject to parallel static electric and magnetic fields has been derived from the linearized coupled Boltzmann-Maxwell equations with the collision frequency assumed to be independent of the particle velocity. The effect of a weak longitudinal electrostatic field, E0, on the propagation characteristic of the right- and left-hand circularly polarized waves in an isothermal electron-proton plasma is examined in detail and illustrated numerically for a conveniently chosen set of the system parameters. For the right-hand polarized wave the electrostatic field effect is found to be significant for a wave with frequency ω in the vicinity of the electron cyclotron frequency ωz ≡ (eB0/m). For example, for a given ω and δ ≡ (eE0/mcω) > 0 an increase in δ, or in E0, leads to the increase or decrease of the attenuation constant α, of the wave according to whether Y ≡ (ωz/ω) < 1 or Y > 1. Moreover, for Y = 1.10, when δ < 0 (i.e., when E0 and the wave vector k are oppositely directed) α increases with |δ|. On the other hand, when δ > 0 an increase in |δ| causes α to decrease and for a sufficiently large value of δ, α may become negative so that the wave may experience a spatial growth.
Some Investigations of Nonlinear Behavior in One-Dimensional Plasmas
Authors: Dawson J. M. , Shanny R.
Published: February 2004

Numerical experiments on a one-dimensional electron plasma were used to obtain an insight into nonlinear plasma phenomena. Three experiments were carried out. The first dealt with the damping of a large-amplitude wave which is found to be much stronger than that predicted by linear theory. A rough theory for the damping is presented. The second experiment examined mode-mode coupling. Quantitative agreement was found with theory after precautions were taken to avoid other effects, in particular, “trapped” particles. A rough theory for “trapping” is given. The third experiment examined the weak turbulence produced by a small bump in the tail of the distribution function, and present theory appears inadequate to describe this behavior. After initial growth, the unstable modes fluctuate on a time scale of 10ωp−1. The bump in the tail of the velocity distribution flattens out in a short time (20ωp−1), and then evolves into a hot Gaussian tail which coexists with the main plasma for a long time (≳ 1000 ωp−1). Particles in the tail have been observed with four times the initial average energy of the beam electron. A discussion of the physical effects which appear to be involved in this experiment is given, and estimates of their importance for three-dimensional plasmas are presented.
Cross-Stream Instability in a Plasma
Authors: Spero Donald M. , Sen Amiya K.
Published: February 2004

A mixed hydromagnetic-electrostatic instability is found propagating perpendicular to the aligned magnetic field and electron streaming in a collisionless plasma. It is found that the growth rate may be comparable to that of the two-stream instability, and there are cases where ions are heated more than electrons. The finite temperature case is considered and thermal damping of the instability is demonstrated.
Determination of Neutral-Atom Density in a Highly Ionized Decaying Hydrogen Plasma
Authors: Forman Peter R. , Kunkel Wulf B.
Published: February 2004

A photoabsorption technique in the vacuum uv region is used to measure the density of atomic hydrogen in a decaying, highly ionized hydrogen plasma as a function of time and position. The plasma is formed in a metal cylinder with a strong axial magnetic field by a powerful pulsed cross-field discharge that takes the form of an axially propagating ionization front. It is found that during the discharge a fraction of the gas is driven to the boundaries forming a layer of increased neutral density which later relaxes back into the plasma by diffusion. In the interior, the plasma is initially highly ionized and the atom density builds up as the ion density decreases. The rate is consistent with predictions based on the collisional-radiative recombination model.
Distribution Function of Energetic Particles Scattered by a Plasma
Authors: Bornatici M. , Engelmann F.
Published: February 2004

It is shown that the distribution of the deflection angles of energetic particles, which travel through a homogeneous and stationary quiescent plasma in the absence of external fields, is Gaussian, if the deflections are small.
Effects of Electron Interactions on the Plasma Thermal Conductivity
Authors: Levinsky E. S. , Rand S.
Published: February 2004

The application of longitudinal wave emission and absorption, to the determination of the thermal conductivity of a fully ionized Lorentz gas, is extended phenomenologically in order to include the effects of electron-electron interactions. A simple modification thereby obtained yields good agreement with the results of previous calculations, which were found by means of formal expansions of the Boltzmann equation about the collision term.
Generation and Motion of Plasmoids in a Magnetic Field with Mirrors
Authors: Jones W. B. , Miller R. D.
Published: February 2004

Plasmoids have been generated in a low-powered theta pinch and accelerated into a uniform longitudinal dc magnetic guide field. The guide field was used to guide the plasmoids into a region between two colinear dc mirrors. The motion of the plasmoids was studied by means of detector coils arranged to measure the diamagnetic effect of the plasmoids. It was found that the plasmoids move in the guide field with uniform velocity, are reflected efficiently by properly chosen mirror fields, and are apparently stable for an observed period of 25 μsec. A pulsed gating coil was arranged in one of the dc mirrors so as to weaken the mirror and allow plasmoids to be gated through the mirror by pulsing the gating coil in the correct phase. Attempts to capture plasmoids between the two mirrors resulted in the plasmoids losing their structure after two reflections between the mirrors and then beginning to expand along the guide field lines. Some measurements were made to determine microscopic characteristics of the plasmoids.
Adiabatic End Loss from a θ Pinch
Authors: Morse Richard L.
Published: February 2004

Collisionless end loss of high β plasma from a θ pinch is estimated from a self-consistent z- dependent equilibrium. The effectiveness of a given vacuum mirror ratio is shown to increase with β and an instability is shown to exist in the mirror region.
Boundary between a Plasma Stream and a Dipole Magnetic Field
Authors: Rubin A. G.
Published: February 2004

The boundary region between a plasma stream and a dipole magnetic field with dipole axis normal to the flow is investigated by means of probes. Simultaneous measurements of the transverse electric field, particle density, magnetic field, and rate of change of magnetic field are made. Oscillations in the electric and magnetic fields are found in the megacycle range. The electric-field oscillations take place in the region of the particle-density gradient, and the magnetic-field oscillations are located at the magnetic-field gradient. The electric-field oscillations are thought to be ion acoustic or magnetoacoustic waves excited by a streaming instability.
First- and Second-Order Corrections to the Magnetic Moment for Linear Multipoles
Authors: Howard James E.
Published: February 2004

The first- and second-order terms in the magnetic moment series have been calculated explicitly for a linear multipole field, using Gardner's general formulas. Computer results show that μ2 is most important for orbits which stay close to a field line.
Comparative Study of Plasma in Toroidal Quadrupole and Octopole Configurations
Authors: Voorhies H. G. , Ohkawa T.
Published: February 2004

A comparison is made between the behavior of plasma in toroidal quadrupole and octopole configurations. The electron temperature is of the order 1 eV and the density 109cm−3. In the octopole configuration, the fluctuations are only observed outside the stability limit predicted by theory. However, such a stability limit cannot be found in the quadrupole configuration because fluctuations are observed throughout the plasma. All the fluctuations have zero wavenumber along the field lines. Waves can be transmitted inside the quadrupole separatrix, and a dispersion relation is measured and compared with the dispersion relation for a drift wave.
Electron Distribution in an Electrostatic Shock
Authors: Tidman D. A. , Fu J. H. M.
Published: February 2004

The consequences of resonant interactions between electrons and ion waves in a turbulent shock wave are discussed.
Kinetic Equation for a Weakly Turbulent Plasma Taking Collisions into Account
Authors: Hatori Tadatsugu
Published: February 2004

Under the assumption that both the nonlinear coupling of waves and wave-particle scattering can be neglected, the collision term is only the sum of the quasilinear term and the nonstationary collision term for the weakly unstable homogeneous plasma.
Some Numerical Results for Two-Dimensional Steady Laminar Bénard Convection
Authors: Plows William H.
Published: February 2004

Results are reported of calculations of the Nusselt number for steady two-dimensional laminar convection in a thin fluid layer between parallel conducting plates. An iterative numerical technique is used to calculate the Nusselt number and the structure of the roll for Rayleigh numbers between 2000 and 22 000 and for Prandtl numbers of 0.5, 1, 2, 6.8, and 200. Comparison with results at Prandtl numbers of 6.8 and ∞ obtained by other investigators using different techniques show good agreement. Discussion is included of the factors affecting accuracy: (1) the zone size in a finite-difference mesh, (2) the number of iteration cycles, and (3) extrapolation from a sequence of meshes to zero zone size. The conclusion is that extrapolation from a pair of grids using 20 and 30 zones per length scale can yield 1% accuracy over the ranges of parameters considered.
Experiments on Rotating Flows between Noncircular Cylinders
Authors: Snyder H. A.
Published: February 2004

Observations have been made on the onset of instability, and on the waveform both at onset and in the finite amplitude region for flows with closed nonrotationally symmetric streamlines. The effect of placing obstacles in the gap between concentric rotating circular cylinders is shown to depend primarily on the extent to which they modify the mean flow. The case of a square inner cylinder and circular outer cylinder is compared with the case of a circular inner cylinder and square outer cylinder. It is shown that the former arrangement, which is time-dependent, is much less stable than the latter. It is concluded that the shape of the boundaries in the Taylor double cylinder problem do not influence the stability markedly, other than by defining the clearance ratio, unless they make the problem time-dependent.
Wake-Induced Effects near the Forward Stagnation Point of a Circular Cylinder
Authors: Smith Mahlon C.
Published: February 2004

Experiments with a circular cylinder in an incompressible, two-dimensional flow show the influence of the unsteady wake on the flow field and heat transfer near the forward stagnation point. Velocity fluctuations, correlations between velocity fluctuations, fluctuation spectra, and the heat transfer near the forward stagnation point were measured and the influence of the wake determined. The wake induces rms u′ velocity fluctuations near the forward stagnation point just outside the boundary layer of about 12%. The u′ fluctuations on opposite sides of the stagnation point have a correlation coefficient of − 1. Energy spectra of the fluctuations show a peak energy density at the cylinder Strouhal frequency. Imposed free-stream turbulence of 6% intensity increases the fluctuations slightly but reduces the correlations significantly. The wake-induced velocity fluctuations do not influence the mean heat transfer near the forward stagnation point.
Flow of a Dissociating Gas past a Convex Corner
Authors: Sundaram T. R.
Published: February 2004

The nonequilibrium flow of an ideal dissociating gas past a convex corner is studied. Linearized theory based on the undisturbed flow is reexamined, and it is shown that it does not give a good quantitative description of the variation of flow quantities along the wall, even for relatively small corner angles. The apparent agreement between the results of linear theory and characteristics solutions reported in earlier work is shown to be due to an ambiguous definition of the characteristic relaxation time. It is only when a characteristic relaxation time based on downstream conditions, rather than upstream conditions, is used in the linearized theory that the results agree reasonably with the numerical calculations. The modified linear theory is used to calculate the increase in entropy along the wall, and it is shown that normal gradients in entropy exist even far downstream of the corner. The calculated increase in entropy along the wall is related explicitly to the asymptotic wall values of the other flow variables, and these values are shown to be different from the infinite-reaction-rate equilibrium values. The calculated asymptotic values are in good agreement with those obtained from numerical calculations.
Slow Compressible Flow past a Circular Cylinder
Authors: Hodnett P. F.
Published: February 2004

The low Reynolds number flow of a gas past an infinite heated circular cylinder is studied for the case of variable property flow when the temperature difference between the cylinder and free stream is small. The perturbation to the corresponding incompressible velocity field is calculated by the method of matched asymptotic expansions developed by Kaplun, and Proudman and Pearson. When the temperature difference between the cylinder and free stream is appreciable, a solution for the velocity field is found on the assumption that the viscosity and thermal conductivity of the gas are invariant. This solution possesses the interesting property that the zero-order solution for the velocity field near the cylinder is a uniformly valid solution of the problem.
Analysis of Axisymmetric Compressible Rotating Free Jets
Authors: Chervinsky A. , Lorenz D. H.
Published: February 2004

Equations governing the flow of a compressible or heated rotating jet far downstream from the orifice, in the neighborhood of the axis of symmetry, are solved in the von Mises plane, and expressions for the axial and radial distributions of velocity and enthalpy are derived. Relations for the retransformation to the physical plane are obtained and computed for specific initial conditions.
Energy Invariant for Geometric Acoustics in a Moving Medium
Authors: Hayes Wallace D.
Published: February 2004

Volume integrals of the quantity E/Ω, where E is the classical acoustic energy density of Rayleigh and Ω is a frequency variable as measured by an observer moving with the medium, are conserved within the assumptions of geometric acoustics in a moving medium whose undisturbed motion is not necessarily steady. With An the area of a ray tube cut by a wave front, the quantity EaAn/Ω2 is constant along a ray. These results generalize classical results of Blokhintsev.
Interaction of External Radiation with an Acoustic Wave
Authors: DePlomb E. P. , Olfe D. B.
Published: February 2004

Calculations are carried out to describe the propagation of an acoustic wave which absorbs energy from an external radiation flux applied instantaneously at the gas boundary. This external radiation is considered to be far out of equilibrium with the gas; therefore, emission of radiation by the gas may be neglected. Two analyses are carried out: (1) a perturbation calculation with the radiation affecting the acoustic wave only through second-order terms, i.e., radiation only slightly perturbs the acoustic wave; (2) an analysis for the transparent limit with the radiation producing a first-order interaction with the acoustic wave, i.e., the acoustic wave is appreciably changed.
Intermediate Strength Blast Wave
Authors: Jones Donald L.
Published: February 2004

Equations for the trajectory and overpressure of the shock front of the intermediate strength blast wave (10 < Δp/p0 ⪝ 0.02) are developed for spherical, cylindrical, and plane blasts. These equations are based on the correct limit method that provided the trajectory of the blast wave from the inverse pinch to velocities below Mach number 1.16 (Δp/p0 = 0.4). The correct limit equations are an extension of the strong shock similarity solution of G. I. Taylor for the spherical blast and A. Sakurai and S. C. Lin for the cylindrical case. It is now possible, given the energy and ambient gas conditions, to trace the shock front trajectory and overpressure from the very strong through the very weak regimes. Conversely, the shock wave energy can be found from measurement of overpressure or arrival time. Comparisons with experimental data as well as the calculations of H. L. Brode verify the validity of the correct limit equations.
Model Dependence of the Temperature Slip Coefficient
Authors: Loyalka S. K. , Ferziger Joel H.
Published: February 2004

The linearized problem of heat flow to a cooled plate embedded in a gas is considered and a variational principle for the temperature slip coefficient is given. This variational principle is then applied to a number of special cases analogous to those considered in an earlier paper on momentum slip coefficient. It is found that the temperature slip coefficient is only slightly model-dependent so that heat-flow calculations with simple models are not likely to be very incorrect.
Flow of Rarefied Gas through a Circular Pipe
Authors: Sone Yoshio , Yamamoto Kyoji
Published: February 2004

The asymptotic behavior at small Knudsen number for two problems involving the flow of rarefied gas through a circular pipe, Poiseuille flow and thermal creep is treated using the Boltzmann-Krook equation. By a matching procedure the outer solution for the continuum regime and the solution for the Knudsen layer are determined simultaneously. Actual calculations have been carried out up to second order. A short discussion on second-order slip condition is also given.
Density Disturbance ahead of a Sphere in Rarefied Supersonic Flow
Authors: Russell David A.
Published: February 2004

An electron-beam x-ray technique was used to obtain precise measurements of the density along the stagnation streamline of spherical models tested in a M = 4.2 (nominal Mach number) nitrogen stream and a M = 3.8 argon stream. Variation of the total pressure and the model radius provided a Re range (based on free-stream properties and model radius) of 30-500 in nitrogen, 100-2000 in argon. The measurements were made with model surface temperatures of 300° K (equal to the total temperature of the flow) and 78° K.
Collision-Dominated Positive Column of a Weakly Ionized Gas
Authors: Blank J. L.
Published: February 2004

To obtain criteria for the validity of the constant coefficient electron diffusion equation, the problem of the positive column is treated using the Boltzmann equation for the electrons. The problem is solved completely for the case of a constant electron-neutral recoil collision time for momentum transfer, in the limit where inelastic collisions play a weak role in determining the shape of the body of the electron distribution function. Here the bulk of electrons is confined by a space charge potential well, and except for a thin boundary layer near the wall, the electron density assumes a Boltzmann distribution, and the electron temperature and diffusion coefficient are constant. For a general collision frequency it is established that, unless the electron energy relaxation length is small compared with the macroscopic length scale, these results are correct only if the following conditions exist: the recoil collision time is reasonably constant over the domain which makes the major contribution to the velocity space moments of the electron distribution function, and the electron fluxes in configuration and velocity spaces are appropriately small.
Hydromagnetic Surface Waves in a Conducting Liquid Surrounded by a Flowing Gas
Authors: Gerwin Richard A.
Published: February 2004

The stability of the interface between a highly conducting liquid and a flowing, nonconducting gas is studied, supposing a magnetic field to be parallel to the interface. Arbitrary angles are allowed between magnetic field, flow direction and wave vector.
Theoretical Study of the Magnetic Field in the Lunar Wake
Authors: Whang Y. C.
Published: February 2004

When the solar wind interacts with the moon, the plasma shadow region on the dark side of the moon forms a long lunar wake. In the plasma umbra a detectable plasma flow is absent and in the penumbra the plasma flux increases from the void condition in the umbra to the interplanetary condition outside. A theoretical model for perturbations of the magnetic field in the plasma shadow is studied by directly solving Maxwell's equations for steady-state solutions. The perturbation of the field is assumed to be due to the magnetization current, the gradient drift current, and the curvature drift current. Numerical solutions are obtained to describe the variations of the magnetic field, and the results are in good agreement with experimental observations from the Explorer 35 satellite.
Quasilinear Theory of Resonant Diffusion in a Magneto-Active, Relativistic Plasma
Authors: Lerche I.
Published: February 2004

Equations are set up to describe the quasilinear behavior of a collisionless, relativistic plasma immersed in a uniform, homogeneous magnetic field. Use of the adiabatic assumption, together with an approximation to resonant denominators, enables an estimate to be given of the change of the distribution function due to the turbulent waves. In the particular cases of pure electrostatic waves, magneto-sonic waves, and cyclotron waves, estimates are made of the rate of energy change of resonant particles. It is shown that some modes exhibit resonant diffusion only when relativistic particles are present and for which there is no nonrelativistic counterpart. It is believed that this calculation may be of some interest in situations where relativistic particles play, or are suspected of playing, a major role; for example, the galactic cosmic ray gas and nonthermal radio sources.
Unified Quasilinear Theory of Weakly Turbulent Plasmas
Authors: Wu C. -S.
Published: February 2004

A quasilinear theory is formulated which includes the microscopic fluctuation fields as well as the coherent waves. The study emphasizes those cases in which the propagating mode of the fluctuation field gives rise to a dominant contribution to the particle correlation. In other words, in these cases the spontaneous Čerenkov emission of plasmons can play a more important role than the two-particle collision process. The instability which is responsible for the turbulence can be of either an electrostatic, electromagnetic, or mixed nature. The effect of an external magnetic field is also considered in the present theory. The final result is valid for an arbitrary ratio of the energy density of the coherent wave to that of the fluctuation field althought the condition of weak turbulence is imposed throughout the analysis.
Statistical Particle Acceleration in Random Fields
Authors: Puri S.
Published: February 2004

Motion of charged particles in arbitrary random electric and magnetic fields is analyzed, and the statistical acceleration rate is derived in terms of power spectra of functions of the applied fields. The treatment is extended to stochastic acceleration in a magnetic mirror; upper and lower bounds (differing by a factor of 2) for the particle acceleration rate are derived for the case when the half-power spectrum of the electric field spans the spectrum of particle gyrofrequencies in the mirror.
Transition of the Dispersion Roots from Beam-Type to Landau-Type Solutions
Authors: O'Neil T. M. , Malmberg J. H.
Published: February 2004

The roots of the dispersion relation describing the linear interaction between a plasma and a relatively low density electron beam are investigated. The dispersion curves exhibit a nontrivial change in topology at a particular value of the appropriately scaled thermal velocity of the beam.
Correlation Measurements of Ion Acoustic Waves in a Highly Ionized Plasma
Authors: Gunshor R. L. , Noon J. H. , Holt E. H.
Published: February 2004

Correlation techniques are applied to low-frequency probe signals detected in a highly ionized hollow-cathode gas-fed arc plasma in an axial magnetic field. One set of oscillations is found to be an ion acoustic wave propagating at an angle to the magnetic field. Drift waves are also observed.
Instabilities in Parametric Oscillations of a Plasma
Authors: Prasad R.
Published: February 2004

Dispersion relations for longitudinal and transverse waves propagated perpendicularly to an externally applied high-frequency electric field in a fully ionized plasma has been obtained. It has been shown that in addition to ω ∼ ω0 (ω0 is the characteristic electron frequency), the longitudinal mode may be excited with frequencies ω ≃ Ωk ± ν (Ωk2 = c2k2 + ω02, ν is the external field frequency); and under certain conditions the excitation near ω0 may be unstable. For the transverse mode instabilities may occur owing to resonance between a backward and a forward moving wave of the same frequency and vice versa. Apparently these are owing to the periodic nature of the dispersion relations found and to the mode-mode coupling present.
Effect of Electron Temperature on Absolute Instabilities in Loss-Cone Plasmas
Authors: Guest G. E. , Dory R. A.
Published: February 2004

Raising electron temperature in an infinite homogeneous plasma of electrons and hot ions tends toward stabilization of the absolute instabilities caused by a nonmonotonic or “loss-cone” distribution of ion velocities perpendicular to the external magnetic field. When the ion plasma frequency exceeds the ion gyrofrequency, this stabilization is incomplete although the residual instabilities have small growth rates and large axial wave lengths, permitting some degree of control by adjusting plasma parameters.