bluuebunny/crossref_metadata_2025 huggingface dataset:
A simple scheme for the direct calculation of ionization potentials with coupled-cluster theory that exploits established excitation energy methods
Authors: Stanton John F. , Gauss Jürgen
Published: July 2002

Vertical ionization potentials can be obtained from existing computer programs for the high-level treatment of excited states by simply including a continuum orbital in the basis set. Exploiting this feature easily allows final state energies for ionized states to be calculated at several previously untested levels of theory that go beyond the equation-of-motion coupled-cluster singles and doubles model. Values obtained for N2, CO, and F2 with the most theoretically complete approximations studied here (those based on the CCSDT-3 and CC3 parametrizations of the neutral ground state) are in excellent agreement with experiment when a large basis set is used.
Multipole moments of water molecules in clusters and ice Ih from first principles calculations
Authors: Batista Enrique R. , Xantheas Sotiris S. , Jónsson Hannes
Published: July 2002

We have calculated molecular multipole moments for water molecules in clusters and in ice Ih by partitioning the charge density obtained from first principles calculations. Various schemes for dividing the electronic charge density among the water molecules were used. They include Bader’s zero flux surfaces and Voronoi partitioning schemes. A comparison was also made with an induction model including dipole, dipole-quadrupole, quadrupole-quadrupole polarizability and first hyperpolarizability as well as fixed octopole and hexadecapole moments. We have found that the different density partitioning schemes lead to widely different values for the molecular multipoles, illustrating how poorly defined molecular multipoles are in clusters and condensed environments. For instance, the magnitude of the molecular dipole moment in ice Ih ranges between 2.3 D and 3.1 D depending on the partitioning scheme used. Within each scheme, though, the value for the molecular dipole moment in ice is larger than in the hexamer. The magnitude of the molecular dipole moment in the clusters shows a monotonic increase from the gas phase value to the one in ice Ih, with the molecular dipole moment in the water ring hexamer being smaller than the one in ice Ih for all the partitioning schemes used.
Relativistic configuration interaction study of the ClF molecule and its emission spectra from 0+ ion-pair states
Authors: Alekseyev Aleksey B. , Liebermann Heinz-Peter , Buenker Robert J. , Kokh Daria B.
Published: July 2002

An ab initio configuration interaction (CI) study including spin–orbit coupling is carried out for numerous valence and ion-pair states of the ClF molecule by employing relativistic effective core potentials. The computed spectroscopic constants are in good agreement with available experimental data for both valence and ion-pair states. The present calculations accurately reproduce the measured spin–orbit splittings for the first Π3 multiplet and confirm the recent corrected spectroscopic parameters for the A 3Π1 state [V. A. Alekseev, D. W. Setser, and J. Tellinghuisen, J. Mol. Spectrosc. 195, 162 (1999)]. The electronic structure of the six lowest ion-pair states of ClF which correlate to the Cl+(3P)+F−(1S) limit is analyzed in detail. It is shown that strong homogeneous perturbations of the E0+ and f0+, β1, and G1 states are mainly caused by an avoided crossing of the 3 3Π and 2 3 Σ− parent Λ–S states. The electric-dipole transition moments have also been calculated for transitions from the E and f ion-pair states to the lower-lying 0+ valence states. Emission spectra for the bound–bound and bound–free transitions have been computed on this basis and found to be in good agreement with the measured spectra. A similar analysis for the ion-pair D′2, β1, and G1 states will be presented in the subsequent study.
Hydrophobic hydration and molecular association in methanol–water mixtures studied by microwave dielectric analysis
Authors: Sato Takaaki , Chiba Akio , Nozaki Ryusuke
Published: July 2002

Dielectric relaxation measurements on the methanol–water mixtures for the entire concentration range were carried out using time domain reflectometry in the frequency range from 500 MHz to 25 GHz at 20, 25, and 30 °C. The excess partial molar activation free energy, enthalpy, and entropy for methanol, ΔGMAE, ΔHMAE, and ΔSMAE, and those for water, ΔGWE, ΔHWE, and ΔSWE, were calculated from accurately measured concentration and temperature dependence of the dielectric relaxation time of the mixtures. The behavior of the excess partial molar quantities in the regions below and above X (molar fraction of methanol) ∼0.3 are quite different from each other. In a water-rich region, ΔHMAE and ΔSMAE exhibit two maxima at X∼0.045 and X∼0.12, which is clearly attributed to structural enhancement of the hydrogen bond network of water, the so-called hydrophobic hydration. Appearance of two maxima in ΔHMAE and ΔSMAE implies that water molecules surround methanol molecules in qualitatively different manners around the two points. In the concentrated region of X⩾0.3, the values of ΔHMAE and ΔSMAE become nearly zero, which means that methanol molecules in the mixtures find themselves in not a very different environment from that in pure methanol, associated and forming chainlike clusters. Water molecules seem to exothermically attach to the hydrophilic site of methanol.
An ab initio quartic force field of PH3
Authors: Wang Dong , Shi Qiang , Zhu Qing-Shi
Published: July 2002

An ab initio quartic force field of PH3 is derived using the coupled-cluster theory with all singles and doubles supplemented with quasiperturbative treatment of the connected triple excitations [CCSD(T)], and Dunning’s correlation consistent polarized valence triple zeta cc-pVTZ basis set. Improved geometry and quadratic force constants are evaluated, respectively, with the correlation consistent polarized valence quadruple zeta cc-pVQZ, core–valence quadruple zeta cc-pCVQZ, and weighted core–valence quadruple zeta cc-pwCVQZ basis sets. In the latter two cases, all electrons are correlated to account for the core correlation effects. Core–valence correlation effect on geometry is found to be significant. By comparing the cc-pCVQZ and cc-pwCVQZ results with the cc-pVQZ ones, the bond length re is reduced by 0.0045 or 0.0049 Å and the bond angle θe by 0.07° or 0.06°, respectively. Cubic and quartic force fields are further determined with the correlation consistent polarized weighted core–valence triple zeta cc-pwCVTZ basis set. Vibrational analysis based on second-order perturbation theory is carried out with the calculated force constants. Computed fundamentals of PH3 agree to better than 4 cm−1 on average with the experimental data. Spectroscopic constants are also predicted for a number of symmetric and asymmetric top isotopomers of PH3. With a minor empirical adjustment of our best force field, agreement of 1 cm−1 between the computed and experimental fundamentals is found for all isotopomers.
Simplicial minisuperspace. II. Some classical solutions on simple triangulations
Authors: Hartle James B.
Published: July 2002

The extrema of the Euclidean Regge gravitational action are investigated numerically for some closed, compact, four-dimensional simplicial manifolds with topologies S4, CP2, and S2×S2.
Representations and invariant equations of E(3)
Authors: Humi Mayer
Published: July 2002

Using methods analogous to those introduced by Gel’fand et al. [Representations of the rotation and Lorentz Groups and Their Applications (Pergamon, New York, 1963)] for the Lorentz group the matrix elements for the representations of the Lie algebra of the Euclidean group in three dimensions E(3) are explicitly derived. These results are then used to construct invariant equations with respect to this group and to show, in particular, that the nonrelativistic analog to the Dirac equation is not unique.
On the initial value problem for a class of nonlinear integral evolution equations including the sine–Hilbert equation
Authors: Santini P. M. , Ablowitz M. J. , Fokas A. S.
Published: July 2002

A method for solving a class of nonlinear singular integral evolution equations for decaying initial values on the line is presented. The underlying scattering problem is a matrix Riemann–Hilbert problem. Scattering analysis shows that the spectrum is purely discrete. An application is to the so-called sine–Hilbert equation Hθt =−c sin θ, where c is a constant and H denotes the Hilbert transform.
Exact solutions for the nonlinear Klein–Gordon and Liouville equations in four-dimensional Euclidean space
Authors: Matsuno Y.
Published: July 2002

A systematic method for constructing particular solutions of the nonlinear Klein–Gordon and Liouville equations in four-spatial dimensions is developed. The method of solution presented here first consists of reducing nonlinear partial differential equations to ordinary differential equations (ODE’s) by introducing symmetry variables and then seeking exact solutions for more tractable ODE’s. Various exact solutions are presented, in which new solutions with nonspherical symmetries are included. Furthermore, the exact method is applied to the above equations in general n-spatial dimensions. Among them, a conformally invariant nonlinear Klein–Gordon equation is particularly interesting from the viewpoint of field theories. The exact solutions for these equations are generalizations of those for the corresponding equations in four-spatial dimensions.
A search for bilinear equations passing Hirota’s three-soliton condition. I. KdV-type bilinear equations
Authors: Hietarinta Jarmo
Published: July 2002

In this paper the results of a search for bilinear equations of the type P(Dx, Dt)F ⋅ F=0, which have three-soliton solutions, are presented. Polynomials up to order 8 have been studied. In addition to the previously known cases of KP, BKP, and DKP equations and their reductions, a new polynomial P=DxDt(Dx2 +√3DxDt+Dt2) +aDx2+bDxDt +cDt2 has been found. Its complete integrability is not known, but it has three-soliton solutions. Infinite sequences of models with linear dispersion manifolds have also been found, e.g., P=DxMDtNDyP, if some powers are odd, and P=DxMDtN(Dx2 −1)P, if M and N are odd.
Solitary waves as fixed points of infinite-dimensional maps for an optical bistable ring cavity: Analysis
Authors: Adachihara H. , McLaughlin D. W. , Moloney J. V. , Newell A. C.
Published: July 2002

The transverse behavior of a laser beam propagating through a bistable optical cavity is investigated analytically and numerically. Numerical experiments that study the (one-dimensional) transverse structure of the steady state profile are described. Mathematical descriptions of (i) an infinite-dimensional map that models the situation, (ii) the solitary waves that represent the transverse steady state structures, (iii) a projection formalism that reduces the infinite-dimensional map to a finite-dimensional one, and (iv) the theoretical analysis of this reduced map are presented in detail. The accuracy of this theoretical analysis is established by comparing its predictions to numerical observations.
Solution to the inverse problem of the 1-D wave equation
Authors: Huang Jau-Inn
Published: July 2002

A general solution for the determination of a variable coefficient in the 1-D wave equation from an additional boundary condition is presented. The Gopinath–Sondhi equation is shown to be a special case of this general solution. One application of this inversion method is to determine the structure of vertically inhomogeneous media from the backscattered waves generated by arbitrary incident waves. When a priori information about the unknown structure is available, a method is presented for the incorporation of this information to stabilize the inversion algorithm.
Quantum inverse scattering method for a nonlinear N-wave resonance interaction system
Authors: Zhou Huan-Qiang , Jiang Lin-Jie
Published: July 2002

The quantum inverse scattering method is used for the study of a nonlinear N-wave resonance interaction system. The Yang–Baxter relations are solved to get various commutation relations for the scattering data operators. The energy spectrum of the quantum Hamiltonian for the model is determined and the existence of the quantum bound states is analyzed. In the classical limit, the corresponding r matrix is found, and the well-established correspondence between the classical solitons and the quantum bound states is examined. Finally, the integrability of the same model but with both fermion fields and boson fields is discussed.
The generalization of the binomial theorem
Authors: Morales J. , Flores-Riveros A.
Published: July 2002

As is well known, the binomial theorem is a classical mathematical relation that can be straightforwardly proved by induction or through a Taylor expansion, albeit it remains valid as long as [A,B]=0. In order to generalize such an important equation to cases where [A,B]≠0, an algebraic approach based on Cauchy’s integral theorem in conjunction with the Baker–Campbell–Hausdorff series is presented that allows a partial extension of the binomial theorem when the commutator [A,B]=c, where c is a constant. Some useful applications of the new proposed generalized binomial formula, such as energy eigenvalues and matrix elements of power, exponential, Gaussian, and arbitrary f(x̂) functions in the one-dimensional harmonic oscillator representation are given. The results here obtained prove to be consistent in comparison to other analytical methods.
Bäcklund transformations for the isospectral and nonisospectral AKNS hierarchies
Authors: Tian C. , Zhang Y. J.
Published: July 2002

By converting the usual Lax pairs for the isospectral and nonisospectral AKNS hierarchies into Lax pairs in Riccati forms, a unified explicit form of Bäcklund transformations for these hierarchies of nonlinear evolution equations can be obtained. In the isospectral case it is an auto-Bäcklund transformation; however, in the nonisospectral case it is not an auto-Bäcklund transformation.
Search for the conformal scalar hair at arbitrary D
Authors: Klimčík Ctirad
Published: July 2002

The recent result that there is no Bekenstein black hole at D≳4 is confirmed by the direct integration of the field equations of the self-gravitating conformal scalar field. The case D=3 where the result turns out to be same is also solved. The curvature singularities of the obtained solutions are analyzed and it is shown that there do exist special (critical) space-times which, however, are of the black hole type only at D=4.
Isogroups and exact solutions for some Klein–Gordon and Liouville-type equations in n-dimensional Euclidean space
Authors: Bhutani O. P. , Bhattacharya Lipika
Published: July 2002

Using the elementary symmetric functions of n Euclidean coordinates xn as symmetry variables and the isovector approach, the generalized forms of nonlinear Klein–Gordon and Liouville equations in n-dimensional Euclidean space are analyzed herein. The construction of the components of the associated isovector field via transport property under Lie derivative leads to orbital equations whose solutions yield invariant groups of transformations. These invariant groups reduce the equations under consideration to nonlinear ordinary differential equations (ODEs) involving arbitrary functions of the new dependent and independent variables. Finally, exact solutions of these resulting ODEs are tabulated for different forms of these arbitrary functions. Beside recovering the available results for particular forms of the said arbitrary functions involved in the ordinary differential equations, some new exact solutions are reported.
Orbit–orbit branching rules between classical simple Lie algebras and maximal reductive subalgebras
Authors: Thoma M. , Sharp R. T.
Published: July 2002

Complete orbit–orbit branching rules are found for the classical algebra–maximal reductive subalgebra pairs Am+n+1⊃Am⊕An⊕u(1), Bm+1⊃Bm⊕u(1), Cm+1⊃Am⊕u(1), Dm+1⊃Dm⊕u(1), and Dm+1⊃Am⊕u(1).
A local variational theory for the Schmidt metric
Authors: Ståhl Fredrik
Published: July 2002

We study local variations of causal curves in a space-time with respect to b-length (or generalized affine parameter length). In a convex normal neighbourhood, causal curves of maximal metric length are geodesics. Using variational arguments, we show that causal curves of minimal b-length in sufficiently small globally hyperbolic sets are geodesics. As an application we obtain a generalization of a theorem by Schmidt, showing that the cluster curve of a partially future imprisoned, future inextendible and future b-incomplete curve must be a null geodesic. We give examples which illustrate that the cluster curve does not have to be closed or incomplete. The theory of variations developed in this work provides a starting point for a Morse theory of b-length.
Langevin approach for Abelian topological gauge theory
Authors: Ohta Y
Published: July 2002

An Abelian topological action is constructed from the quantization of Seiberg–Witten monopole equations as “Langevin equations.” The starting point is an analogous action to the Labastida–Pernici’s non-supersymmetric action for Donaldson theory. As the local symmetry of the action is first stage reducible, the quantum action is obtained by using Batalin–Vilkovisky quantization procedure. We can also obtain off-shell quantum action and BRST transformation.
Diffusion on braided spaces
Authors: Franz U. , Schott R.
Published: July 2002

The notion of q-Brownian motion introduced by Majid is extended to braided spaces corresponding to a generic R-matrix, and combined with the theory of quantum probability. This leads to a definition of diffusions on these spaces. The corresponding heat equations (difference-differential equations) are solved in terms of Appell polynomials (i.e., shifted moment systems). Some examples of interest for applications are given.
Quantum group structure on the quantum plane
Authors: Tahri E. H.
Published: July 2002

We show that the quantum plane introduced by Manin is a quantum group according to the Faddeev–Reshetikhin–Takhtajan approach. We give its matrix representation, R-matrix, and its Hopf structure. Some quantum properties of the quantum matrix whose elements generate the quantum plane are also discussed.
Uniqueness theorems for classical four-vector fields in Euclidean and Minkowski spaces
Authors: Woodside Dale A.
Published: July 2002

Euclidean and Minkowski four-space uniqueness theorems are derived which yield a new perspective of classical four-vector fields. The Euclidean four-space uniqueness theorem is based on a Euclidean four-vector identity which is analogous to an identity used in Helmholtz’s theorem on the uniqueness of three-vector fields. A Minkowski space identity and uniqueness theorem can be formulated from first principles and the space components of this identity turn out to reduce to the three-vector Helmholtz’s identity in a static Newtonian limit. A further result is a uniqueness theorem for scalar fields based on an identity which is proved to be a static Newtonian limit of the zeroth or scalar component of the Minkowski space extension of the Helmholtz identity. Last, the three-vector Helmholtz identity and uniqueness theorem and their four-space extensions to Minkowski space are generalized to mass damped fields.
Integral representations of thermodynamic 1PI Green’s functions in the world-line formalism
Authors: Sato Haru-Tada
Published: July 2002

The issue discussed is a thermodynamic version of the Bern–Kosower master amplitude formula, which contains all necessary one-loop Feynman diagrams. It is demonstrated how the master amplitude at finite values of temperature and chemical potential can be formulated within the framework of the world-line formalism. In particular we present an elegant method of how to introduce a chemical potential for a loop in the master formula. Various useful integral formulas for the master amplitude are then obtained. The nonanalytic property of the master formula is also derived in the zero temperature limit with the value of chemical potential kept finite.
A field theory approach to Lindstedt series for hyperbolic tori in three time scales problems
Authors: Gallavotti G. , Gentile G. , Mastropietro V.
Published: July 2002

Interacting systems consisting of two rotators and a pendulum are considered, in a case in which the uncoupled systems have three very different characteristic time scales. The abundance of unstable quasiperiodic motions in phase space is studied via the Lindstedt series regarded as a sum of Feynman graphs and studied with renormalization group techniques based on Eliasson’s work on KAM tori. The result is a strong improvement, compared to our previous results, on the domain of validity of bounds that imply existence of invariant tori, large homoclinic angles, long heteroclinic chains, and drift-diffusion in phase space.
On the validity of Taylor’s hypothesis for wall-bounded flows
Authors: Piomelli Ugo , Balint Jean-Louis , Wallace James M.
Published: July 2002

The results of large eddy simulation (LES) of the Navier–Stokes equations are used to evaluate the validity of Taylor’s hypothesis of frozen turbulence, which states that the time derivative of some instantaneous quantity is proportional to its derivative in the streamwise direction, for incompressible plane channel flow. Time and space derivatives in the streamwise direction of the velocity components are, in fact, found to be well correlated. Root-mean-square fluctuations of the terms in Taylor’s hypothesis also support the validity of this hypothesis above the buffer layer. The good agreement between LES and experimental results indicates that errors in the evaluation of derivatives in the streamwise direction are due mostly to insufficient resolution.
A model for near-wall turbulence
Authors: Haritonidis Joseph H.
Published: July 2002

A model for near-wall turbulence based on a modified mixing length hypothesis and the bursting process in the wall region of a turbulent boundary layer yields a mean velocity profile valid from the wall to the beginning of the logarithmic region, in good agreement with experimental measurements. The mean velocity profile, as well as the stramwise and transverse fluctuation levels, are related to the bursting frequency.
Turbulent dynamo effect and cross helicity in magnetohydrodynamic flows
Authors: Hamba Fujihiro
Published: July 2002

A three-dimensional direct simulation of inhomogeneous magnetohydrodynamic (MHD) turbulence is carried out to investigate the turbulent dynamo effect. The velocity field is driven by an external force so that the velocity and magnetic fields are statistically inhomogeneous in one direction and homogeneous in the other two directions. Several statistical quantities are obtained such as the mean magnetic field, the turbulent energy, and the turbulent electromotive force. The data are used to examine the modeling of the dynamo effect in the four-equation turbulence model. It is shown that the dynamo term related to the cross helicity is more important than the well-known α dynamo term. Some model constants in the four-equation model are estimated using the least-square method.
On the behavior of velocity gradient tensor invariants in direct numerical simulations of turbulence
Authors: Cantwell Brian J.
Published: July 2002

Studies of direct numerical simulations of incompressible, homogeneous, and inhomogeneous turbulence indicate that, in regions of high kinetic energy dissipation rate, the geometry of the local velocity gradient field has a universal character. The velocity gradient tensor satisfies the nonlinear evolution equation (dAij/dt)+AikAkj−1/3 (AmnAnm)δij=Hij where Aij=∂ui/∂xj and the tensor Hij contains terms involving the action of cross derivatives of the pressure field and viscous diffusion of Aij. The restricted Euler equation corresponding to Hij=0 can be solved in closed form [Cantwell, Phys. Fluids A 4, 782 (1992)] and the solution has the property that, for any initial condition, Aij(t) evolves to an asymptotic state of the form Aij(t)≂Kij[R(t)]1/3 where R(t) is a function which becomes singular in a finite time and Kij is a constant matrix. A number of the universal features of fine-scale motions observed in direct numerical simulations are reproduced by Kij.

In the simulation studies the first invariant of Aij is zero by incompressibility. The second and third invariants, Q and R, are determined at every grid point in the flow and the entire data set is cross-plotted to search for significant features in the space of tensor invariants. Such features can then be associated with corresponding local flow structures in physical space. When a variety of incompressible simulations are studied, scatter plots of Q vs R reveal that a fairly significant fraction of the data lies in the lower right quadrant. This is consistent with behavior predicted by the restricted Euler solution. However, the bulk of the data lies more or less uniformly distributed in a slightly elliptical region about the origin. In a direct numerical simulation of a plane, time-developing, mixing layer a small fraction of the data collects along a very pronounced, nearly straight, ridgeline extending into the upper left quadrant. This data can be traced to regions with local vorticity much larger than the local strain lying within streamwise rib vortices which connect adjacent spanwise rollers in the mixing layer simulation. Neither the predominant tendency for Q and R to lie near the origin nor the possibility for Q and R to lie far from the origin in the upper left quadrant are predicted by the restricted Euler solution. The purpose of this paper is to show that, by relaxing the assumption Hij=0 while retaining a model of dAij/dt motivated by the asymptotic form of the restricted Euler solution, one can begin to account for these features of the (Q,R) scatter plots. The results suggest that the velocity gradient tensor in three-dimensional flow tends to evolve toward an attractor in the space of tensor invariants. A significant feature of the model is that, although Hij≠0, singular behavior of Aij(t) can still occur along specific paths in the (Q,R) plane corresponding to zero values of the discriminant of Hij.
Periodic flow in the near wake of straight circular cylinders
Authors: Plaschko Peter , Berger Eberhard , Peralta-Fabi Ramón
Published: July 2002

The formation of periodic waves in the near wake of straight circular cylinders with arbitrary aspect ratios in crosswise flows at low Reynolds numbers (Re) is analyzed. Using a semiempirical model it is shown that raising the Reynolds number beyond a critical value of about Re(1)=22 yields a supercritical Hopf bifurcation preceding the known onset of the von Kármán vortex flow at about Re(2)=46.7. In agreement with experimental trends a stable periodic, secondary transversal motion arises in the previously steady crosswise flow.
Relativistic phase fluctuations of beat wave accelerators and wakeless triple solitons
Authors: Osuga T. , Mima K. , Takabe H. , Tajima T.
Published: July 2002

The coupled wave equations for two incident laser beams, their cascade beams, and a relativistic electron plasma wave are numerically analyzed to show phase fluctuations of the acceleration field. It is found that the phase fluctuations are induced by the relativistic nonlinear shift of the plasma frequency together with the electromagnetic pump wave depletion. When the phase fluctuations become significant, the accelerated particle energy is reduced strongly. The triple-soliton concept, which is proposed to overcome the above difficulties, is also numerically investigated. In particular, effects of the relativistic nonlinearity and the frequency mismatch are discussed. The numerical analysis clarified that the appropriate initial frequency mismatch cancels the relativistic nonlinearity, as indicated by McKinstrie and DuBois [Phys. Rev. Lett. 57, 2022 (1986)] and the triple-soliton propagates for a long distance.
Stabilization of the absolute instability in cyclotron autoresonance maser amplifiers by a drive wave
Authors: Lin A. T. , Lin Chih-Chien
Published: July 2002

It is demonstrated through computer simulations that a cyclotron autoresonance maser (CARM) amplifier with finite output pulse width operated in a high-order waveguide mode, such as the TE01 mode, is feasible. This is because the absolute instability grows from the initial beam noise fluctuation and takes a certain time interval to become disruptive to the desired amplification process. A drive wave with sufficiently high intensity can further reduce the growth rate of the absolute instability and prolong the stable amplification period.
Neoclassical viscosity effects on resistive magnetohydrodynamic modes in toroidal geometry
Authors: Yang J. G. , Oh Y. H. , Choi D. I. , Kim J. Y. , Horton W.
Published: July 2002

The flux-surface-averaged linearized resistive magnetohydrodynamic (MHD) boundary-layer equations including the compressibility, diamagnetic drift, and neoclassical viscosity terms are derived in toroidal geometry. These equations describe the resistive layer dynamics of resistive MHD modes over the collisionality regime between the banana plateau and the Pfirsch–Schlüter. From the resulting equations, the effects of neoclassical viscosity on the stability of the tearing and resistive ballooning modes are investigated numerically. Also, a study is given for the problem of how the neoclassical resistive MHD mode is generated as the collisionality is reduced. It is shown that the neoclassical viscosity terms give a significant destabilizing effect for the tearing and resistive ballooning modes. This destabilization comes mainly from the reduction of the stabilizing effect of the parallel ion sound compression by the ion neoclassical viscosity. In the banana-plateau collisionality limit, where the compressibility is negligible, the dispersion relations of the tearing and resistive ballooning modes reduce to the same form, with the threshold value of the driving force given by Δc=0. On the other hand, with the finite neoclassical effect it is found that the neoclassical resistive MHD instability is generated in agreement with previous results. Furthermore, it is shown that this later instability can be generated in a wide range of the collisionality including near the Pfirsch–Schlüter regime as well as the banana-plateau regime, suggesting that this mode is a probable cause of anomalous transport.
Short-wavelength electromagnetic fluctuations and anomalous electron energy transport in collisional tokamak edges
Authors: Saleem H. , Shukla P. K.
Published: July 2002

It is shown that free energy stored in the equilibrium electron density and temperature gradients can drive short-wavelength electromagnetic fluctuations in collisional plasmas embedded in a homogeneous magnetic field. The enhanced electromagnetic fluctuations can cause anomalous cross-field electron energy transport. The present investigation can have relevance to short scale electric and magnetic field fluctuations, as well as anomalous thermal conduction in tokamak edges.
Stabilizing effect of dissipative-trapped electrons on the energetic ion modes
Authors: Hirose A.
Published: July 2002

It is shown that dissipative-trapped electrons have a significant stabilizing influence on long-wavelength magnetohydrodynamic (MHD) modes driven unstable by energetic ions. For modes with m (the poloidal mode number)=𝒪(10), an electron collisionality parameter of the order ν*e≂𝒪(10−2) is sufficient to deactivate the instabilities.
Central magnetohydrodynamic activity in pellet-fueled JT-60 plasmas
Authors: Kamada Y. , Ozeki T. , Azumi M.
Published: July 2002

The central magnetohydrodynamic (MHD) activities are strongly affected by hydrogen pellet injection. The change in the sawtooth characteristics (viz., crash time, crash mechanisms, and sawtooth period) seem to be dependent on the density (and pressure) peakedness. With deepening pellet penetration, the sawtooth frequency becomes longer. At the sawtooth emerging after the deep pellet penetration into high-Ip limiter discharges, only a small amount of the central kinetic energy is released and the crash does not follow the fully reconnecting style. The sawtooth crash after the pellet injection tends to have more ideal-like characteristics for higher density and pressure peaking factors. At each sawtooth, the m=1 rotation frequency changes suddenly to the ion-diamagnetic direction or the codirection (parallel to the plasma current).
Measurement of current drive profile using electron cyclotron wave attenuation near the O-mode cutoff
Authors: Fidone I. , Meyer R. L. , Caron X.
Published: July 2002

A method for determining the radial profile of the lower-hybrid current drive in tokamaks using electron cyclotron attenuation of the O mode for frequencies ω near the cutoff frequency is discussed. The basic idea is that, for a given wave frequency, the cutoff plays the role of a spatial filter selecting a variable portion of the noninductive current. It is shown that the incremental attenuation resulting from a small increase of ω displays specific features related to the current density near the cutoff point. Using the relation between the wave damping and the current density, it is possible to determine the radial profile of the current drive from the wave attenuation measurements. A numerical application is also presented for plasma parameters in the reactor regime.
Free boundary resistive modes in tokamaks
Authors: Huysmans G. T. A. , Goedbloed J. P. , Kerner W.
Published: July 2002

There exist a number of observations of magnetohydrodynamic (MHD) activity that can be related to resistive MHD modes localized near the plasma boundary. To study the stability of these modes, a free boundary description of the plasma is essential. The resistive plasma–vacuum boundary conditions have been implemented in the fully toroidal resistive spectral code castor (Complex Alfvén Spectrum in Toroidal Geometry) [Proceedings of the 18th Conference on Controlled Fusion and Plasma Physics, Berlin, edited by P. Bachmann and D. C. Robinson (European Physical Society, Petit-Lancy, Switzerland, 1991), p. 89]. The influence of a free boundary, as compared to a fixed boundary on the stability of low-m tearing modes, is studied. It is found that the stabilizing (toroidal) effect of a finite pressure due the plasma compression is lost in the free boundary case for modes localized near the boundary. Since the stabilization due to the favorable average curvature in combination with a pressure gradient near the boundary is small, the influence of the pressure on the stability is much less important for free boundary modes than for fixed boundary modes.
Relations between spectra of spatial derivatives of temperature in a turbulent jet
Authors: Antonia R. A. , Browne L. W. B. , Chambers A. J.
Published: July 2002

The spectrum of the lateral derivative of temperature has been measured on the center line of a turbulent plane jet and compared with calculations, based on local isotropy, derived from the spectra of either the streamwise derivative or the temporal derivative of temperature. To within the experimental uncertainty, quantitative agreement between measurement and calculation is satisfactory for sufficiently large wavenumbers.
Dynamics of a gas mixture in an extended kinetic theory
Authors: Boffi V. C. , Franceschini V. , Spiga G.
Published: July 2002

The dynamics of a mixture of N rarefied gases is studied by analyzing the set of nonlinear continuity equations for the number densities. Removal and regeneration effects are also taken into account. Various physical situations are considered, corresponding to N=2 and N=3. The relevant diagrams (trajectories in the phase space and curves of the single densities as functions of time) are reported and briefly discussed on physical grounds.
Comments on ‘‘Bifurcation phenomena and the radial electric field in a nonaxisymmetric plasma’’ [Phys. Fluids 2
9, 536 (1986)]
Authors: Catto Peter J. , Myra J. R. , Hastings D. E.
Published: July 2002

The smallest total collisional entropy production rate technique of choosing among multiple ambipolar roots is contrasted with a linearized stability method in which only the ambipolar potential is perturbed.
Self-consistent theory of a harmonic gyroklystron with a minimum Q cavity
Authors: Tran T. M. , Kreischer K. E. , Temkin R. J.
Published: July 2002

In this paper, the energy extraction stage of the gyroklystron [in Advances in Electronics and Electron Physics, edited by C. Marton (Academic, New York, 1979), Vol. 1, pp. 1–54], with a minimum Q cavity is investigated by using a self-consistent radio-frequency (rf) field model. In the low-field, low-current limit, expressions for the self-consistent field and the resulting energy extraction efficiency are derived analytically for an arbitrary cyclotron harmonic number. To our knowledge, these are the first analytic results for the self-consistent field structure and efficiency of a gyrotron device. The large signal regime analysis is carried out by numerically integrating the coupled self-consistent equations. Several examples in this regime are presented.
Evolution of flow in the developing region of the mixing layer with a skew laminar wake as an initial condition
Authors: Miau Jiun-Jih , Karlsson Sture K. F.
Published: July 2002

The mixing layer was studied at a Reynolds number (U1δ*/ν) of 270 and at six velocity ratios ranging from 1.0 to 0.46. Velocity measurements were carried out in the developing region of the mixing layer. Results show that naturally developing velocity fluctuations reach the maximum at a certain stream location in the developing region, then decay, and that the streamwise velocity fluctuation increases again in the further downstream region where the mean flow approaches the hyperbolic-tangent shape. There is an indication that the fluctuating motion initiated in the wake region with its characteristic scale can pick up additional energy in the downstream hyperbolic-tangent mean-flow region, although stability theory predicts a most unstable length scale that is substantially larger.
Nonlinear gyrokinetic theory, the direct interaction approximation, and anomalous thermal transport in tokamaks
Authors: Hagan W. K. , Frieman E. A.
Published: July 2002

Invariance properties under scale transformations of the nonlinear gyrokinetic Vlasov and heat transport equations are used to examine anomalous thermal transport due to drift wave turbulence. To fully exploit the gyrokinetic expansion, separation of the fluctuations from the background by means of averaging is required. This leads to a statistical description of the system and the use of the direct interaction approximation. The invariance properties of the gyrokinetic and statistical descriptions produce the same results for χ, the thermal diffusivity. For a collisionless, low-β, quasineutral plasma in a general magnetic field, a unique result is derived for χ.
Coulomb scattering between Maxwellian plasma and monoenergetic beam
Authors: Riedler J. M. , Miley G. H. , Heindler M.
Published: July 2002

The use of the theory of generalized function to solve the linearized Fokker–Planck equation for certain special cases is illustrated. As an example, an infinitely extended fusion plasma is considered where the lost particles are continuously refueled by injection of monoenergetic particles perpendicular to the magnetic field lines. The stationary velocity distribution of the injected particles during scattering with a Maxwellian background plasma is calculated. A local solution is presented for the case where the density of the non-Maxwellian component of the distribution is less than ∼10% of the total. Resulting plots of the velocity distribution are presented and the extension of the technique to other situations discussed.
Classical single-particle dynamics of the anomalous Doppler resonance
Authors: Dendy R. O.
Published: July 2002

A gyroaveraged Lagrangian is used to describe the motion of a single electron undergoing anomalous Doppler resonance with a wave that has both electrostatic and electromagnetic components, propagating at arbitrary inclination to the magnetic field. It is shown that the flows of parallel and perpendicular energy are oppositely directed, and have magnitudes in the ratio 1+ω/(Ω/γ):1. The change in perpendicular kinetic energy, or equivalently Larmor radius, is related very simply to the E×B drift occurring at Landau resonance. The classical single-particle description of the anomalous Doppler resonance underlies the existing classical collective descriptions, and is the classical counterpart to the well-known quantum single-particle description.
Linear stability for plane relativistic shock waves
Authors: Anile A. M. , Russo G.
Published: July 2002

The linear stability of a plane relativistic shock has been investigated. Restrictions are found on the equation of state in order for the shock to be stable. A comparison is made with the results obtained in the framework of (nonlinear) corrugation stability.
Current driven weak double layers under linearly stable conditions
Authors: Verga A. D. , Chanteur G. , Pellat R.
Published: July 2002

Extensive one-dimensional Vlasov simulations have been performed in order to study the dynamics of double-layer generation in a stable current carrying plasma. An initial density perturbation, which shortly builds a potential well, leads to a weak double layer and to a recurrent formation of electron vortices for a large range of temperature ratios and electron drift velocities. The electron–vortex formation is inhibited for very small velocity drifts. While the electrostatic energy is generally almost constant, a weak growth develops for an electron drift velocity that is sufficiently high, but less than the critical drift velocity for marginal stability. The amplitude of individual double layers is rather weak, but the collision of two double layers drives a nonlinear instability related to the fusion of electron vortices, amplifying the double-layer potential to several times the electron thermal energy.
A time-dependent model for railgun plasma armatures
Authors: Batteh Jad H. , Rolader Glenn E. , Powell John D. , Desai Prateen V.
Published: July 2002

In this paper a one-dimensional, time-dependent model is described for the analysis of railgun plasma armatures. The model assumes that the armature is isothermal, and that the electrical conductivity and degree of ionization in the plasma are uniform and constant in time. The model is applied to the analysis of three problems—armature initiation, armature response to a change in current, and armature response to a change in mass. In each case, the perturbation induces damped oscillations in the armature length and projectile acceleration about the corresponding steady-state values. The period of the oscillations is, for early times, approximately equal to 3leq/a0, where leq is the equilibrium armature length corresponding to the steady-state solution and a0 is the acoustic propagation velocity in the plasma. The exponential decay time for the cases studied ranges from 140 to 200 μsec. Although most calculations are completely numerical, a partly analytic, limiting-case perturbation solution of the governing equations is also carried out. This analysis suggests why the same oscillation period is obtained in all three cases. The impact of transient phenomena on gun performance and diagnostics, as well as plans for additional analyses, are discussed.
Effect of a self-generated dc-magnetic field on forward Raman scattering and hot electrons in laser produced plasmas
Authors: Sharma R. P. , Dragila R.
Published: July 2002

A study is made of (forward) stimulated Raman scattering in the presence of a background dc-magnetic field. Two special cases have been considered: when the pump laser beam propagates (i) perpendicular to the background magnetic field as an elliptically polarized extraordinary wave, and (ii) along the background magnetic field as a right/left-hand circularly polarized wave. Explicit expressions for the growth rate and threshold power are presented. It has been demonstrated that the background magnetic field can significantly affect the growth rate and threshold for forward Raman scattering and the temperature of hot electrons.
The fine-scale intermittency of turbulence
Authors: Britz D. , Shah D. A. , Antonia R. A.
Published: July 2002

The technique of Rao et al. [J. Fluid Mech. 48, 339 (1971)], which consists of identifying pulses or regions of strong activity in a narrow bandpass filtered signal, is reexamined in the context of Sreenivasan’s theory [J. Fluid Mech. 151, 81 (1985)], by applying it to white noise and turbulent signals. For white noise, the dependence of pulse characteristics on the threshold and filter center frequency are in close agreement with the theory. There are, however, important differences between white noise and turbulence results, even when the white noise spectrum is shaped to simulate the turbulent spectrum. For the turbulent signal, the theory is valid only for a range of filter parameters for which the departure of the filtered signal from a Gaussian distribution is small. Using wall shear stress and velocity fluctuations in a fully developed turbulent duct flow, the pulse frequency is found to be closely related to the zero-crossing frequency. It is concluded that the pulse frequency, which is proportional to the Kolmogorov frequency, cannot scale on outer variables.
Closure of the Reynolds stress and scalar flux equations
Authors: Jones W. P. , Musonge P.
Published: July 2002

A second-order, single-point closure model for calculating the transport of momentum and passive scalar quantities in turbulent flows is described. Of the unknown terms that appear in the Reynolds stress and scalar flux balance equations, it is those which involve the fluctuating pressure that exert a dominant influence in the majority of turbulent flows. A closure approximation (linear in the Reynolds stress) has been formulated for the velocity-pressure gradient correlation appearing in the Reynolds stress equation. When this is used in conjunction with previous proposals for the other unknown terms in the stress equation, the proposed model closely simulates most of the data on high Reynolds number homogeneous turbulent flows. For the fluctuating scalar-pressure gradient correlation appearing in the scalar flux equation, an approximation has been devised that satisfies the linear transformation properties of the exact equation. Additional characteristics of the fluctuating scalar field are obtained from the solution of modeled balance equations for the scalar variance and its ‘‘dissipation’’ rate. The resulting complete scalar field model is capable of reproducing measured data in decaying scalar grid turbulence and strongly sheared, nearly homogeneous flow in the presence of a mean scalar gradient. In addition, applications to the thermal mixing layer developing downstream from a partially heated grid and to a slightly heated plane jet issuing into stagnant surrounds result in calculated profiles in close agreement with those measured.
Linear dependence of the bulk viscosity on shock wave thickness
Authors: Emanuel George , Argrow Brian M.
Published: July 2002

Currently, the bulk viscosity μb of a gas can only be obtained with an acoustic absorption experiment. A method is proposed that is primarily applicable to a dense polyatomic gas. In this circumstance, the density-based thickness Λρ is large, consisting of many thousands of mean-free paths. Moreover, the ratio μb/μ (μ is the shear viscosity) is linear with this thickness. Consequently, shock measurements of Λρ can be used to evaluate μb. The approach is illustrated using sulfur hexaflouride.