bluuebunny/crossref_metadata_2025 huggingface dataset:
Noniterative method for constructing many-parameter solutions of the Einstein and Einstein–Maxwell field equations
Authors: Guo Dong-sheng
Published: March 2003

We present a noniterative method of executing a large class of Kinnersley–Chitre transformations in both the vacuum and the electrovac case. By solving the homogeneous Hilbert problem in the Hauser–Ernst formalism, we generate new many-parameter solutions of the Einstein equations. In the vacuum case, the solution is a natural generalization of the N-fold Neugebauer solution, while, in the electrovac case, we have a natural generalization of the N-fold Cosgrove solution worked out by Wang, Guo, and Wu.
Pure radiation fields admitting nontrivial null symmetries
Authors: Radhakrishna L. , Singh N.Ibohal
Published: March 2003

The sixteen types of geometrical symmetries corresponding to the continuous groups of collineations and motions generated by a null vector n are considered. The common propagation vector of a pure electromagnetic radiation field and a pure gravitational radiation field is chosen to be n. For such radiation fields all the sixteen symmetries are expressed in terms of the Newman–Penrose (NP) spin coefficients and then it is shown that when n is a gradient field there are only five independent symmetries. The existence of these five nontrivial null symmetries is established by finding exact solutions of Einstein–Maxwell field equations when n satisfies freedom conditions and when l of the NP null tetrad (l, m, m̄, n) is shear-free. Thus a class of space-times of pure radiation fields that admit (i) a Ricci collineation which is not a curvature collineation (CC), (ii) a CC which is not a special curvature collineation (SCC), (iii) a SCC which is not an affine collineation (AC), (iv) an AC which is not a motion, and (v) a motion is determined.
On the validity and practical applicability of derivative analyticity relations
Authors: Kolář P. , Fischer J.
Published: March 2003

We examine derivative analyticity relations (DAR), which were originally proposed by Bronzan as an alternative to dispersion relations and in which the dispersion integral is replaced by a tangent series of derivatives. We characterize the class of functions satisfying DAR, and show that outside this class the dispersion integral represents a Borel-like sum of tangent series. We point out difficulties connected with the application of DAR.
Self-gravitating isotropic and anisotropic fluid distributions
Authors: Krori K. D. , Nandy D.
Published: March 2003

Some exact solutions of isotropic and anisotropic fluid distributions in general relativity have been generated in this paper on the basis of the Letelier theory of fluids.
A generalization of the Siewert–Burniston method for the determination of zeros of analytic functions
Authors: Anastasselou E. G. , Ioakimidis N. I.
Published: March 2003

The Siewert–Burniston method for the derivation of closed-form formulas for the zeros of sectionally analytic functions with a discontinuity interval along the real axis (based on the Riemann–Hilbert boundary value problem in complex analysis) is generalized to apply to the determination of the zeros of analytic functions (without discontinuity intervals) inside or outside simple smooth contours. An application of this method to the closed-form solution of the transcendental equation zez =beb, appearing in the theory of neutron moderation in nuclear reactors, is also made.
Closing and abelizing operatorial gauge algebra generated by first class constraints
Authors: Batalin I. A. , Fradkin E. S.
Published: March 2003

A canonical transformation of operators of relativistic phase space is constructed, which abelizes the basis of the operator-valued gauge algebra of first class constraints. The new operators of contraints commute among themselves. The new Hamiltonian commutes with the constraints. Dynamics of the new operators is physically equivalent to the initial one.
Anharmonic oscillators and generalized hypergeometric functions
Authors: Codaccioni J. P. , Caboz R.
Published: March 2003

A large class of anharmonic oscillators represented by the Hamiltonian H(q, p)= 1/2 p2+ 1/2 ω20q2 +λqα (α integer >2) is considered. Owing to an integration technique using the Lagrange–Bürmann theorem, one can give for the period and the action integral of bounded motions closed expressions in terms of energy in the form of very simple generalized hypergeometric functions. Finally an application of the method is given for doubly anharmonic oscillators.
Hamilton–Jacobi theory for constrained systems
Authors: Dominici D. , Longhi G. , Gomis J. , Pons J. M.
Published: March 2003

We extend the Hamilton–Jacobi formulation to constrained dynamical systems. The discussion covers both the case of first-class constraints alone and that of first- and second-class constraints combined. The Hamilton–Dirac equations are recovered as characteristic of the system of partial differential equations satisfied by the Hamilton–Jacobi function.
A construction relating Clifford algebras and Cayley–Dickson algebras
Authors: Wene G. P.
Published: March 2003

A review of the applications of the octonions in physics is given. A construction is presented. Both the Cayley–Dickson algebras and the Clifford algebras arise naturally under this construction from the quaternion algebras. The mathematical properties of the algebras constructed are discussed.
Partially coherent states of the real symplectic group
Authors: Deenen J. , Quesne C.
Published: March 2003

In the present paper, we introduce partially coherent states for the positive discrete series irreducible representations 〈λd+n/2,...,λ1+n/2〉 of Sp(2d,R), encountered in physical applications. These states are characterized by both continuous and discrete labels. The latter specify the row of the irreducible representation [λ1λ2⋅⋅⋅λd] of the maximal compact subgroup U(d), while the former parametrize an element of the factor space Sp(2d,R)/H, where H is the Sp(2d,R) subgroup leaving the [λ1λ2⋅⋅⋅λd] representation space invariant. We consider three classes of partially coherent states, respectively, generalizing the Perelomov and Barut–Girardello coherent states, as well as some recently introduced intermediate coherent states. We prove that each family of partially coherent states forms an overcomplete set in the representation space of 〈λd+n/2,...,λ1+n/2〉, and study its generating function properties. We show that it leads to a representation of the Sp(2d,R) generators in the form of differential operator matrices. Finally, we relate the latter to a boson representation, namely a generalized Dyson representation in the cases of Perelomov and Barut-Girardello partially coherent states, and a generalized Holstein–Primakoff representation in that of the intermediate partially coherent states.
Shape functions for separable solutions to cross-field diffusion problems
Authors: Luning C. D. , Perry W. L.
Published: March 2003

The shape function S(x), which arises in the study of nonlinear diffusion for cross-field diffusion in plasmas, satisfies the equation S″(x)+λa(x)Sα(x)=0, 0<x<1, S(0)=S(1)=0, α>0. In the cases of physical interest a(x) possesses an integrable singularity at some point in (0,1) but is otherwise continuous. Existence of a positive solution to this problem is established.
Poisson structure of the equations of ideal multispecies fluid electrodynamics
Authors: Spencer Richard G.
Published: March 2003

The equations of the two- (or multi-) fluid model of plasma physics are recast in Hamiltonian form, following general methods of symplectic geometry. The dynamical variables are the fields of physical interest, but are noncanonical, so that the Poisson bracket in the theory is not the standard one. However, it is a skew-symmetric bilinear form which, from the method of derivation, automatically satisfies the Jacobi identity; therefore, this noncanonical structure has all the essential properties of a canonical Poisson bracket.
Probability distributions with given multivariate marginals
Authors: Cohen Leon
Published: March 2003

A method is presented for obtaining joint probability density functions which satisfy given multivariate marginal densities.
On a pointlike relativistic massive and spinning particle
Authors: Bette Andreas
Published: March 2003

A pointlike massive and spinning relativistic particle is described as a confined system of two massless directly interacting spinning constituents. The approach is Hamiltonian. The employed phase space is, thus, a symplectic vector space equipped with global canonical and Poincaré-covariant twistor coordinates. The Poincaré-invariant generator of the phase space motion does not represent the energy of the total system. Consequently, the evolution parameter cannot be identified with the time. The generating function, however, makes the position four vector and the proper time of the composite massive and spinning system into dynamical variables, i.e., functions of the evolution parameter. The phase flow may thus be interpreted as a simple particle dynamics in Minkowski space. In analogy with the definition of Bakamjian and Thomas for the center of energy of a relativistic massive and spinning particle, a definition of the center of energy of a massless particle with nonvanishing helicity is presented.
Electromagnetic effects in an elastic circular cylindrical waveguide
Authors: Green A. E. , Naghdi P. M.
Published: March 2003

The problem of wave propagation in an elastic, thin circular cylindrical tube, including the possibility of propagation of rotating waves, is examined with the use of a nonlinear electromagnetic membrane theory. Some related special cases, which include wave propagation in a class of magnetic polarized rigid tubes and rigid plates, are also briefly discussed.
On the RHS description of resonances and virtual states
Authors: Gadella M.
Published: March 2003

We discuss the role of the M≂ller wave operators in a rigged Hilbert space (RHS) model for resonances. We also construct a new RHS of analytic functions valid for the description of resonances and virtual states. These become generalized state vectors in a general physically realizable representation.
A method of calculating the function of two noncommuting operators
Authors: Moretti P. , Mancini M.
Published: March 2003

A method is developed of evaluating a function of the sum of two noncommuting Hermitian operators. A physical example is given and a summation formula is obtained.
Effect of the boundary condition at distance of closest approach on Wien dissociation of a weak electrolyte: A singular perturbation solution
Authors: McIlroy Douglas K. , Mason David P.
Published: March 2003

A singular perturbation technique is developed in order to examine the effect of plausible variations in the boundary condition of the ion-pair distribution function f at the distance of closest approach of the oppositely charged ions in a weakly dissociated electrolyte. Such variations from the point-ion model may arise in practice where the ions are weakly solvated or in ion-exchange resins or soluble polyelectrolytes. The relative increase K(X)/K(0) in the dissociation constant of the weak electrolyte to which a uniform electric field X is applied is calculated to third order in the field-dependent parameter ε, assuming that the mean distance of closest approach between the charge centers of oppositely charged ions, a, is nonzero. A novel feature of this problem is that the boundary condition on f at distance a depends on the dissociation constant itself. It is found that the constant of proportionality in Onsager’s linear law, derived for the idealized case of a weakly dissociated electrolyte of point ions, remains unchanged when a≠0 but the second- and third-order terms in the expansion for K(X)/K(0) in powers of ε are each increased by an additional term which is proportional to exp (−1/a).
A superspace approach to lattice supersymmetry
Authors: Kostelecký V. Alan , Rabin Jeffrey M.
Published: March 2003

We construct a cubic lattice of discrete points in superspace, as well as a discrete subgroup of the supersymmetry group which maps this ‘‘superlattice’’ into itself. We discuss the connection between this structure and previous versions of lattice supersymmetry. Our approach clarifies the mathematical problems of formulating supersymmetric lattice field theories and suggests new methods for attacking them.
Symmetry properties of the configuration interaction space in relation to one- and two-particle operators: The splitting theorem
Authors: Živković Tomislav P.
Published: March 2003

The configuration interaction (CI) space Xn built upon n electrons moving over 2n orthonormalized orbitals χi is considered. It is shown that the space Xn splits into two complementary subspaces X+n and X−n having special properties: each state Ψ+∈X+n and Ψ−∈X−n is ‘‘alternantlike’’ in the sense that it has a uniform charge density distribution over all orbitals χi and vanishing bond-orders between all orbitals of the same parity. In addition, matrix elements Γ(ij;kl) of a two-particle density matrix vanish whenever four distinct orbitals are involved and there is an odd number of orbitals of the same parity. Further, Γ(ij;lj)=γ(il)/4 ( j≠i,l), whenever (i) and (l) are of different parity. This last relation shows the connection between a two-particle (Γ) and a one-particle (γ) density matrix. ‘‘Elementary’’ alternant and antialternant operators are identified. These operators connect either only the states in the same subspace, or only the states in different subspaces, and each one- and two-particle symmetric operator can be represented by their linear combination. Alternant Hamiltonians, which can be represented as linear combinations of elementary alternant operators, have alternantlike eigenstates. It is also shown that each symmetric Hamiltonian possessing alternantlike eigenstates can be represented as such a linear combination. In particular, the PPP Hamiltonian describing an alternant hydrocarbon system is such a case. Complementary subspaces X+n and X−n can be explicitly constructed using the so-called regular resonance structures (RRS’s) which are normalized determinants containing mutually disjunct bond orbitals. Expressions for the derivation of matrix elements of one- and two-particle operators between different RRS’s are also derived.
Direct problem of image processing
Authors: Szu Harold H.
Published: March 2003

Matched filters of image processing are revisited from the viewpoint of Wiener’s regulations of the ill-posed problem and the superresolution. For both the object-independent image processing and the object-matched pattern recognition, the minimum mean-square image spread (MMIS) filters are derived from a general constrained moment expansion method, which includes Wiener’s method based on the performance criteria: minimum mean square estimation errors (MMSE) as a special case.
V*-algebras: A particular class of unbounded operator algebras
Authors: Epifanio Giuseppina , Trapani Camillo
Published: March 2003

We consider a weak unbounded commutant for a set of unbounded operators and we examine op*-algebras which coincide with some of their bicommutant. This class of op*-algebras, called V*-algebras, shows some properties close to those which hold true for bounded operator algebras.
Double phase-integral approximations: A systematic simplification technique for wave equations with cutoffs and resonances
Authors: Skorupski Andrzej A.
Published: March 2003

The time-independent wave equation, d2ψ/dz2+Q2(z)ψ=0, where Q2(z) may have arbitrary order zeros and poles on or close to the real axis, is transformed to a simpler wave equation of similar properties (model). Approximate transformations leading from the original wave equation to the model are simply related to Fröman’s higher-order phase integrals, but are nevertheless well defined at the pertinent zeros and poles of Q2(z).
An infinite chain of inequalities for correlation functions of classical lattice systems
Authors: Naudts J.
Published: March 2003

In quantum-mechanical systems the moments of the symmetrized time-dependent autocorrelation function satisfy an infinite set of chained inequalities. By analogy the same inequalities are derived for correlation functions of classical lattice systems.
Impulsive motion of a circular disk which causes a vortex ring
Authors: Sallet D. W.
Published: March 2003

Vortex ring parameters such as circulation and translational velocity are estimated from the impulsive motion of a circular disk which generates the vortex ring. A comparison between predicted values of the vortex ring parameters and actually measured values is given.
Observation of cellular patterns in a partly filled, horizontal, rotating cylinder
Authors: Karweit M. J. , Corrsin S.
Published: March 2003

The liquid in a partly filled, horizontal, rotating circular cylinder displays at least three different types of periodic, cellular motion. Two of these, which have apparently not heretofore been presented, are described.
Thermal conductivity of neon from heat transfer measurements in the continuum and temperature−jump regimes
Authors: Jody B. J. , Saxena S. C.
Published: March 2003

A general hot−wire column type of experimental facility is described in its developed form for the unambiguous and accurate study of heat transfer from a heated wire to the surrounding gas. In particular, the measurements are reported for heated tungsten and platinum wires in neon for the temperature range 50° to 2450°C. The thermal conductivity values are determined from the heat transfer rate measurements in the continuum and temperature−jump regimes. The thermal conductivity values are compared with the conductivity and viscosity measurements of other workers, with the predictions based on the principle of corresponding states, and with the calculations based on kinetic theory in conjunction with the various spherically symmetric intermolecular potentials.
Shock wave stability
Authors: Swan G. W. , Fowles G. R.
Published: March 2003

The D’yakov work which deals with a shock that undergoes a slight disturbance is re−examined. Under a linear analysis the growth of perturbations is examined and this produces inequality restrictions for the shock to be stable. It is found that the shock is unstable for j2(dv/dp)H 〈−1 and j2(dv/dp)H〉 1 + 2M, where M is the Mach number of the shock with respect to the material behind, and −j2 is the slope of the Rayleigh line. These inequalities agree with those of D’yakov. It is also shown that these results are exactly the same as those derived by Erpenbeck by a different analysis. Some properties of general Hugoniot curves are also presented. It is demonstrated that the restriction to M<1, by itself, does not restrict the range of values for the slope of the Hugoniot curve.
Approximate solutions of the Boltzmann equation for shock waves. II
Authors: Sather Norman F. , Lin Chen Jung
Published: March 2003

An approximate solution of the Boltzmann equation for shock waves is obtained by a procedure which is an extension of the methods of Mott−Smith and of Salwen, Grosch, and Ziering. Shock thicknesses for the density, velocity, and temperature profiles are calculated for Mach numbers from 1.05 to infinity, and the numerical convergence of the results of the three methods is discussed.
Electron heating in collisional shocks
Authors: McNeill Donald H.
Published: March 2003

Thomson scattering of ruby laser light at 90° was used to obtain electron temperature and density profiles for plasmas produced by strong collisional shock waves. Transverse (B1 ≠ 0) shocks of speed 3−25 cm/μsec in 50−100 mTorr deuterium were studied. Plasma created by reflecting a strong shock from a dielectric wall was also studied. It is found, in agreement with theoretical expectations, that the electron temperature (10−30 eV) is much lower than the ion temperature (100−500 eV) immediately after shock heating of the plasma. Temperature equilibration between ions and electrons, however, does not take place in the times of observation (2−4 μsec). It is shown that initial electron heating in the plasma is caused primarily by Ohmic dissipation of currents in the shock structure. For pure gas ionizing shocks (B1 = 0), the measured electron temperature is in good agreement with theory.
Perturbation of plasma by stratified electromagnetic radiation
Authors: Woods C. H.
Published: March 2003

An analysis is presented of the density perturbation produced in a warm plasma by a stratified electromagnetic wave. Filamented wavefields of arbitrary polarization with an intensity distribution which is doubly periodic in the transverse coordinates are considered. The analysis is based on second−order perturbation theory, and comparisons are made with the procedure leading to the well−known ponderomotive potential.
Behavior of the sideband instability
Authors: Van Hoven Gerard , Jahns Gary
Published: March 2003

The mechanism of the trapped−electron instability of a large−amplitude wave is revealed by the following experimental observations: Sideband waves exhibit an initial enhanced damping (examined by the use of linear test excitations) for a distance ∼λb′ the large−wave oscillation length. Beyond this point, the unstable waves grow with a rate linearly proportional to the main−wave electric potential. Measurements show that the instability growth depends on the initial amplitude of the large wave and can persist after this wave field has decayed by tens of decibels. This implication that the driving force of the instability resides in the particles is substantiated by direct measurements of the electron distribution function which, in the presence of a large wave, is found to develop a ’’bump−on−the−tail’’ of sufficient magnitude to account for the observed sideband growth.
High−vacuum trapping experiments on the astron
Authors: Hester R. E. , Porter G. D. , Stallard B. W. , Taska J. , Walker C. W. , Weiss P. B.
Published: March 2003

Experimental results of high−vacuum (10−7 to 10−6 Torr) E−layer trapping experiments on the astron are presented. Both single and multiple pulse experiments are reported. The precessional mode is stabilized with a toroidal field. At sufficiently low pressures (≲5×10−6 Torr), E layers were observed to be stable for up to 200 msec. For greater times, the applied toroidal field had decayed sufficiently so that the layer was unstable to precessions. Axial compression of the layer was observed as it was neutralized by ionization of the background gas. Compressions by a factor of two were observed. For layers whose self−well is the dominant focusing force, this compression agrees with adiabatic theory. A small (≈20%) E−layer loss was observed during the compression. It is felt that this loss arises from scattering in electric field inhomogeneities. The effect of resistive walls on trapping efficiency was studied and it was shown that the efficiency scales with the theoretically calculated energy loss in the resistive walls. Finally, the results of the multiple pulse experiments are presented. Failure to achieve buildup of the E layer is attributed to a combination of losses during compression and poor trapping efficiency on later pulses.
Surface waves of finite amplitude in axisymmetric swirling flow
Authors: Hickox Charles E.
Published: March 2003

A novel perturbation technique originally proposed by Benjamin is applied to the study of surface waves in axisymmetric, swirling flow of an inviscid fluid. A first approximation to finite amplitude waves of large wavelength is obtained. The results are found to correspond to the classical solitary and conidial wave solutions given by Korteweg and deVries.
Comparison of theory and experiment for homogeneous turbulence with shear
Authors: Deissler R. G.
Published: March 2003

Solutions for uniformly-sheared turbulence, in which the interaction of the turbulence with the mean shear dominates the turbulent self-interaction, are compared with experiment. An anisotropic spectral tensor, which appears general enough to represent the initial experimental turbulence, is used for the initial condition in the calculations. The evolution of one-point turbulence components and microscales, as well as two-point velocity correlations, are considered. In most cases the agreement with experiment is good. The theory correctly predicts the presence of a negative region for two-point longitudinal-velocity correlations only for point separations in the direction normal to the flow and the mean gradient.
Form of the turbulence dissipation equation as applied to curved and rotating turbulent flows
Authors: Raj Rishi
Published: March 2003

An exact turbulence dissipation equation in the generalized relative system is presented. Simplified forms of the equation are obtained for computational purposes in the high Reynolds number approximation. Modeling of the rotation term is proposed. Modeling of the other higher-order terms is also presented in a generalized system using the tensor invariance technique. An estimate of the angular velocity is provided for the rotation term to be included in the turbulence dissipation equation. The associated significant curvature terms for turbomachinery flows are also identified.
Multipoint distribution function hierarchy for compressible turbulent flow
Authors: Fox Ronald L.
Published: March 2003

The hierarchy of equations for the multipoint distribution functions is developed for compressible turbulent flow. The compressible equations reduce to previously published relations for incompressible fluids with constant transport under the appropriate approximations. Expressions for other types of incompressible fluids are also shown to be derivable from the compressible relations.
Behavior of burst diaphragms in shock tubes
Authors: Hickman Roy S. , Farrar Larry C. , Kyser James B.
Published: March 2003

Analytical and experimental studies have been carried out on the behavior of strong shock tube diaphragms. These diaphragms exhibit large moments of resistance to opening due to stresses at the hinge line of the diaphragm petal. High speed shadowgraph photographs of the detailed opening process have been obtained and have been shown to compare well with the analytical model derived for flowfield-diaphragm interaction. A nondimensional resistance parameter is shown to control the behavior of the thick diaphragm and the detailed flow process which controls the opening is identified.
Frequency and damping of ion acoustic waves
Authors: Ono M. , Kulsrud R. M.
Published: March 2003

The frequency and damping of ion-acoustic waves in a singly ionized plasma have been determined for wave lengths at which collisions are important but not dominant and for electron-ion temperature ratios of 0.5, 1, 2, and 4, by numerically solving the linearized Fokker–Planck equation. The collisional and collisionless limits are in good agreement with existing theory. As a by-product the ion viscosity and thermal conductivity were evaluated and agreed with those of Braginskii.
Modulational stability of the ion plasma mode
Authors: Chan V. S. , Seshadri S. R.
Published: March 2003

The cubic Schrödinger equation satisfied by the slowly varying amplitude of the longitudinal wave in an electron-ion plasma is deduced using the method of Kakutani and Sugimoto. The analysis of the Schrödinger equation shows that the ion acoustic wave is modulationally stable and that the ion plasma oscillations are modulationally stable or unstable according to whether the wavenumber is below or above a critical value which is controlled entirely by the wave dispersion.
Cascade heating in a laser irradiated plasma
Authors: Yuen S. Y.
Published: March 2003

A nonlinear electromagnetic theory is developed for studying the interaction of laser radiation with the collective waves of a two-component warm plasma. Analytic expressions are obtained for steady-state (time-saturation) spectra and wave energies of the Langmuir and ion-acoustic fluctuations excited by parametric decay instabilities. The dominant nonlinear mechanism treated is the coherent excitation of secondary electrostatic waves by the Langmuir oscillation, so that the results are directly relevant when the electron temperature far exceeds the ion temperature. Threshold values for these secondary excitations are determined. Effective anomalous absorption coefficients for electrons and ions are also calculated. The nature of the depletion nonlinearity is discussed.
Optimal laser plasma heating in a solenoidal magnetic field
Authors: Vagners J. , Neal R. D. , Vlases G. C.
Published: March 2003

Laser heating of a plasma column confined by a solenoidal magnetic field is studied via modern optimal control techniques. Plasma density and temperature at a given axial position along the plasma column are assumed to be uniform in the radial direction but time varying; the (local) laser intensity as a function of time is taken as the control. Classical absorption of laser energy by the electrons through the mechanism of inverse bremsstrahlung is assumed, with ion heating resulting from collisional energy transfer. It is also assumed that electrical conductivity is very large, so that particle diffusion and Ohmic heating are negligible. The theory for determining optimal laser pulse shapes in time, I (t), to achieve specified performance criteria is then developed and applied to the problem of raising the ion temperature from an initial equilibrium value to a prescribed level in minimum time. Constraints on the maximum laser intensity and energy available are imposed and typical numerical results presented.
Stability of a diffuse, high β, l=1 system
Authors: Berge G. , Freidberg J. P.
Published: March 2003

A stability analysis for a diffuse high β, l=1 helical system is presented. It is shown that there exists a gross m=1 mode whose properties are very similar to those predicted by sharp boundary theory. In addidion, two new classes of m=1 modes are found. One is a set of interior localized modes and the other a set of modes localized exterior to the plasma. The growth rate of these modes is quite small. The internal mode exists for any monotonic pressure profile and cannot be wall stabilized. Its effect on experimental plasmas is as yet unknown.
Equilibrium properties of a rotating nonneutral E layer in a cusped magnetic field
Authors: Striffler C. D. , Kapetanakos C. A. , Davidson R. C.
Published: March 2003

The equilibrium properties of a nonneutral rotating E layer confined in a linear cusped magnetic field are examined within the framework of the steady-state nonrelativistic Vlasov–Maxwell equations. In order to eliminate the radial loss of electrons at the symmetry plane of the cusp, a negative voltage is applied on a section of the cylindrical conductor that surrounds the E layer. The effects of the applied cusped magnetic field and the applied potential on the boundaries of the region occupied by the electrons, together with the influence of the equilibrium space-charge effects, are calculated self-consistently. The specific choice of equilibrium distribution function is one for which all electrons have the same total energy and the same canonical angular momentum. The electron density has a 1/r spatial dependence within the E layer and the azimuthal velocity profile is different before and after the cusp transition region. The region occupied in configuration space is reduced in size when the applied voltage is increased. Upper limits are found to exist on the applied and self-field potentials in order that the E layer occupy a continuous space in the axial direction. A brief discussion of electrostatic stability properties as well as a qualitative comparison with pertinent experimental observations is presented.
Plasma potential in electrostatically plugged cusps and mirrors
Authors: Dolan T. J. , Stansfield B. L. , Larsen J. M.
Published: March 2003

From a study of the particle balance equations for ions and electrons confined by a combination of electric and magnetic fields, the potential barrier heights are determined. The theoretical potential well depths are found to be about 20–30% shallower than experimentally measured values, which may be attributed to inaccuracy of the velocity-diffusion loss rates and to uncertainty in experimental parameters.
Antenna response to random electric fields due to thermodynamic density fluctuations in plasmas
Authors: Grabowski R.
Published: March 2003

Thermodynamic density fluctuations of positively and negatively charged components in a plasma are responsible for the occurrence of random electric fields. The response of an antenna to these fields may be characterized by the quadratic or power spectrum of the voltage fluctuations in a measuring device connected to the antenna. The response depends upon the antenna configuration and is described as a filtering effect in wave vector space. Theoretical quadratic spectra are presented for equilibrium plasmas streaming parallel to the antenna axis. The bulk velocity has a strong influence upon the shape of the spectra, especially as it produces a periodic structure.
Plasma production from solid targets with laser radiation prepulses
Authors: Parbhakar K. J. , Nguyen Duc-Long
Published: March 2003

Plasma production from solid targets by prepulses is discussed. The influence of the time interval between the prepulses and the giant pulse on the density distribution is considered.
Improved variational method for axisymmetric plasmas
Authors: Shumaker D. E. , Bernstein I. B.
Published: March 2003

An improved variational method for determining transport coefficients in axisymmetric plasmas is given. The advantage of the method is that the induction electric field is determined as an independent unknown and can be approximated by means of trial functions.
Magnetohydrodynamic stability of a sharp boundary model of tokamak
Authors: Freidberg J. P. , Grossmann W.
Published: March 2003

Calculations of critical β for a sharp boundary, constant pressure model of tokamak are presented. The analysis is valid for arbitrary β, arbitrary aspect ratio, and arbitrary plasma cross section. Specific results are given for the circle, ellipse, triangle, square, and doublet cross sections.
Direct integration method applied to Soret-driven instability
Authors: Chock David P.
Published: March 2003

A direct integration approach coupled with Newton’s iteration scheme was devised to determine the linear stability of a hydrodynamic system with general boundary conditions. A fundamental set of linearly independent solutions was constructed whose coefficients are to be determined by the boundary conditions. In order to assure the existence of nontrivial solutions for the coefficients, a secular equation must be solved whose solution determines the stability criteria to an arbitrary degree of accuracy. This method was applied to a two-component liquid system with rigid-rigid boundaries and an imposed temperature gradient. No approximation was made of the Soret-effect term and of the primary-state configuration. A slope discontinuity was found in the critical Rayleigh number as the Soret coefficient increases in the positive region. The frequency of the oscillatory mode was found to be very sensitive to the variation of the negative Soret coefficient near the bifurcation point, and to the variation of the concentration near zero or unity. Comparison with existing experiments is also discussed.
Long waves on a thin fluid layer flowing down an inclined plane
Authors: Nakaya C.
Published: March 2003

Long nonlinear waves on a thin fluid layer flowing down an inclined plane are investigated. For the condition of the Weber number of order one, the equation for the free surface is computed to the third-order accuracy of the shallow water parameter. The development of a long monochromatic wave is analyzed by use of this equation. Near the upper branch of the neutral curve, the original steady flow is found to be supercritically stable and the amplitude of the monochromatic wave is determined. The stretching of the eigenfrequency by nonlinearity has no definite sign. For a comparatively large wavenumber, the wave velocity can be smaller than that of the linear wave. The nonexistence of the periodic wave in the region far from the upper branch of the neutral curve is discussed in connection with the temporally growing solution of the equation in order to determine the second harmonic.
Quasi-steady droplet vaporization theory with property variations
Authors: Law C. K.
Published: March 2003

A theory is developed to account for the variable nature of the specific heat C and the transport coefficients of thermal and mass diffusion, λ and D, for the quasi-steady equilibrium vaporization of a droplet in an unbounded, stagnant atmosphere. In the theory C, λ, and D are all temperature dependent whereas C and λ are further concentration weighted. Results from the present theory are found to agree within 15% with existing numerical solutions.
Thickness of an embedded ion shock
Authors: Greywall Mahesh S.
Published: March 2003

The thickness of an ion shock embedded in a collisional shock propagating in an electron proton gas is calculated, using both the kinetic theory and the continuum approach, for the free stream Mach numbers M=3 to M→∞. It is found that the shock thickness predicted by the kinetic theory is 2–4 times the thickness obtained from the continuum approach. It is also found that the electric field, via which the electrons are compressed across the ion shock, although representing considerable dissipation of the ion kinetic energy, has very little effect on the ion shock broadening.
Wakes in collisionless plasma
Authors: Fournier Gérard , Pigache Daniel
Published: March 2003

Wakes at mesothermal conditions are studied in a plasma wind tunnel which simulates ionospheric flight conditions. The need for a very low pressure in the chamber, provided by a liquid-helium trap, is shown. Wakes of bodies large with respect to the Debye length are investigated and the ratio Te/Ti (electron temperature/ion temperature) can be varied. For Te/Ti≫1, an ion density peak arises in the midwake and ion waves propagate in the far wake. For Te/Ti≈1, peaks and waves are entirely suppressed. A quantitative agreement with different theories is achieved.
Measurement of the development and evolution of shock waves in a laser-induced gas breakdown plasma
Authors: Chu T. K. , Johnson L. C.
Published: March 2003

Space- and time-resolved interferometric measurements of electron density in CO2-laser produced plasmas in helium or hydrogen are made near the laser focal spot. Immediately after breakdown, a rapidly growing region of approximately uniform plasma density appears at the focal spot. After a few tens of nanoseconds, shock waves are formed, propagating both transverse and parallel to the incident laser beam direction. Behind the transverse propagating shock is an on-axis density minimum, which results in laser-beam self-trapping. The shock wave propagating toward the focusing lens effectively shields the interior plasma from the incident beam because the lower plasma temperature and higher plasma density in the shock allow strong absorption of the incident beam energy. By arranging the laser radiation-plasma interaction to begin at a plasma-vacuum interface at the exit of a free-expansion jet, this backward propagating shock wave is eliminated, thus permitting efficient energy deposition in the plasma interior.
Electronic thermal conductivity in low-temperature afterglow plasmas
Authors: Gauthier J-C. , Delpech J-F.
Published: March 2003

Electronic thermal conductivity has been measured in afterglows of low-power discharges in helium, neon, and mixtures of both gases over a broad range of electron and neutral concentrations down to cryogenic electron and neutral temperatures (40 °K and 25 °K, respectively). Detailed results were obtained from dominant electron-neutral to dominant Coulomb interactions. In the latter case explicit dependence of transport parameters on the number ND of electrons in a Debye sphere was sought down to the lowest value where measurements were possible in our experimental system (ND=4). Data and tables are given to allow accurate computation of electronic thermal conductivity in the rare gases for any degree of ionization at electron temperatures up to 10 000 °K. Our experimental results support, within statistical error bars, generally accepted electronic transport theory taking into account simultaneous electron-neutral and Coulomb interactions over the range of plasma parameters covered and particularly down to the lowest number of electrons in a Debye sphere.
Effect of phase-correlated electrons on whistler wavepacket propagation
Authors: Denavit J. , Sudan R. N.
Published: March 2003

The evolution of large-amplitude whistler wavepackets in a hot collisionless plasma is examined. When resonant electrons are trapped in the wave during a transit time, they acquire a correlation in phase of their perpendicular velocities relative to the local wave magnetic field, which causes new emissions and elongates the wavepacket in the direction of emergence of the resonant electrons. This is explained in terms of equations of propagation for the wavepacket amplitude, wavenumber, and frequency, involving phase correlated particles. The results of computer simulations showing the elongation of large-amplitude wavepackets, and the wavenumber and frequency characteristics of the new emission are presented.
Macroscopic properties of the inverse theta-pinch effect
Authors: Kondoh Yoshiomi , Itoh Kazuo , Nagao Shigeo
Published: March 2003

Macroscopic properties of the inverse theta pinch are investigated. It is found that the second and succeeding explosions of this pinch begin soon after each peak of the oscillatory coil current, whereas the first explosion begins at the first increase in the current. It is also found that the velocity v of this pinch depends on the mass density ρ0 of the gas and on the peak coil current density im approximately as v∝ρ0−1/4 im1/2 for the first explosion, and as v∝ρ0−1/6 im1/3 for the second and succeeding explosions. These new experimental observations are analyzed theoretically.
Stability of mean turbulent flows
Authors: Ahmadi Goodarz
Published: March 2003

The stability of mean turbulent motion is studied via energy method. Several restrictions on the Reynolds stress tensor are derived to insure the stability of mean motion. The classical models of Boussinesq and Prandtl are considered and estimates of eddy viscosity and mixing length are obtained.
Influence of velocity sensitivity on the statistics of small scale temperature fluctuations
Authors: Antonia R. A.
Published: March 2003

The theoretical temperature spectrum used by Wyngaard is not consistent with spectra measured in the atmospheric surface layer and leads to a significant overestimation of the effect of velocity sensitivity of a resistance-wire temperature sensor on the skewness of the temperature derivative.
Derivation of connection formulas for wave conversion in inhomogeneous plasma
Authors: Peratt A. L.
Published: March 2003

Connection formulas relevant to the description of wave conversion in inhomogeneous plasma have been derived.
Quasi-linear spectrum of current driven ion cyclotron waves
Authors: Harvey R. W.
Published: March 2003

Quasi-linear theory is applied to the current-driven, longitudinal ion cyclotron instability in a magnetized, collisional electron-proton plasma. A quasi-stationary state, consisting of a balance between current excitation of the spectrum and collisional effects, is obtained when the applied electric field is marginally greater than instability threshold. This state ceases to exist when quasi-linear diffusion of the protons exceeds velocity space collisional diffusion. Solution of the ion kinetic equation is by an iterative technique utilizing variational properties of the collision operator. Results are considered with the context of the solar wind plasma.
Onset, growth, and saturation of the current-driven ion cyclotron instability
Authors: Correll D. L. , Rynn N. , Böhmer H.
Published: March 2003

The temporal evolution of the current-driven electrostatic ion cyclotron instability was investigated experimentally. The critical destabilizing electron drift velocity for different values of mode phase velocity was measured. The phase velocity was changed by varying the effective plasma column length and hence the parallel wavelength. Ion cyclotron damping was observed to dominate over electron Landau damping at low phase velocities. The temporal growth rate was experimentally determined for several values of electron drift and found to agree very well with linear theory. The observed saturated mode amplitudes compare favorably with the saturation levels predicted by a theory of nonlinear stabilization due to wave induced collisions.
Saturation spectrum of the parametric decay instability in the presence of an external magnetic field
Authors: Chen H. C. , Fejer J. A.
Published: March 2003

The effects of an external magnetic field on the saturation spectrum of parametric instabilities are calculated and are discussed in the context of ionospheric heating experiments.
Two-dimensional unidirectional turbulent flow in a local equilibrium
Authors: Naot D.
Published: March 2003

A solution for the six Reynolds stresses is given. The mean flow is unidirectional in the x direction, and has derivatives of the same order of magnitude in both the y and the z directions. The application of the solution as boundary conditions near corners is discussed.
Phase locking the auto-resonant accelerator
Authors: Lohr John
Published: March 2003

The normal development of the beam-plasma instability to a broadened fluctuation spectrum can be retarded by the injection of a plasma wave at the most unstable frequency.
Hydromagnetic boundary layers in a rotating cylindrical container
Authors: Vempaty Somaraju , Loper David E.
Published: March 2003

Linear, steady, axisymmetric flow of an electrically conducting homogeneous fluid confined within a rigid, rotating electrically insulated cylinder is analyzed. The fluid motions are driven by differential rotation of horizontal boundaries. The applied magnetic field and the rotation vector are aligned normal to the horizontal boundaries. The magnetic Reynolds number, the Rossby number, and the Ekman number are assumed to be much less than unity. The dynamics of the inviscid interior and vertical boundary layers are investigated as functions of the rotational magnetic interaction parameter α2(=σB2/2ρΩ) which measures the ratio between the magnetic force and the Coriolis force. If α2 ≪1, the flow behaves as a nonmagnetic rotational flow to dominant order with Stewartson’s E1/3 and E1/4 double layer structures and the electric currents pumped by the Ekman–Hartmann layer return through the interior. At the other extreme, if α2≫E−1/3 the flow behaves as a strongly magnetic nonrotational flow with a single vertical layer (≈E1/4 α−1/2) of parabolic structure. The intermediate range 1≪α2≪E−1/3, which is a transition from weakly magnetic to the strongly magnetic flows, is characterized by a quadruple vertical boundary layer structure: (1) a nonmagnetic E1/3 layer, (2) a nonmagnetic E1/4α1/2 layer, (3) a magnetic α−2 layer to transport the electric current vertically, and (4) a magnetic E1/4α−1/2 layer with axial scale E1/4α3/2 to feed to feed the current from the Ekman–Hartmann layers into the α−2 layer.
Motion of a vortex pair approaching an opening in a boundary
Authors: Karweit Michael
Published: March 2003

The flow properties of liquid helium are such that the motions of vortex rings and line vortices can be calculated from hydrodynamic potential theory. The two-dimensional (line vortex) case allows a relatively simple method of calculating vortex motion: The ’’Routh path function’’ yields a solution through conformal mapping. Using this method, the case of a rectilinear vortex pair approaching a slit in a wall is analyzed. Criteria for their just passing through are found.