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322 results on '"Balescu, Radu"'

1. V-Langevin Equations, Continuous Time Random Walks and Fractional Diffusion

Author

Balescu, Radu

Subjects
Physics - Plasma Physics, Physics - Data Analysis, Statistics and Probability
Abstract

The following question is addressed: under what conditions can a strange diffusive process, defined by a semi-dynamical V-Langevin equation or its associated Hybrid kinetic equation (HKE), be described by an equivalent purely stochastic process, defined by a Continuous Time Random Walk (CTRW) or by a Fractional Differential Equation (FDE)? More specifically, does there exist a class of V-Langevin equations with long-range (algebraic) velocity temporal correlation, that leads to a time-fractional superdiffusive process? The answer is always affirmative in one dimension. It is always negative in two dimensions: any algebraically decaying temporal velocity correlation (with a Gaussian spatial correlation) produces a normal diffusive process. General conditions relating the diffusive nature of the process to the temporal exponent of the Lagrangian velocity correlation (in Corrsin approximation) are derived., Comment: Latex 69 pages including 23 EPS figures

Published
2007
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2. S

Author

Fowles, Grant R., Whetten, N. Rey, Bolt, Bruce A., Dresselhaus, Mildred S., Sze, S. M., O’Neil, Stephen J., Gupta, Y. M., Arya, Atam P., Corbin, John C., Burkhard, Donald G., Mcdaniels, David K., Zarem, A. M., Erway, Duane D., Mohler, Orren C., Willson, Richard C., Wert, Charles A., Kunz, A. Barry, Johnson, Francis S., Shutt, R. P., Sakai, Hajime, De Wames, R. E., Wolfram, T., Armstrong, H. L., Cunningham, R. G., Montgomery, D. J., Jammer, Max, Balescu, Radu C., Wolf, Frank L., Matthews, P. T., Chandrasekhar, B. S., Lane, C. T., Unertl, W. N., Harasima, Akira, Wolfe, Hugh C., White, Milton G., and Besançon, Robert M., editor

Published
1990
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7. Anisotropic electrostatic turbulence and zonal flow generation

Author

Balescu, Radu, Petrisor, Iulian, Negrea, Marian, Balescu, Radu, Petrisor, Iulian, and Negrea, Marian

Abstract

In this paper we analyse the running and asymptotic diffusion coefficients of a plasma in the case of zonal flow generation by an anisotropic stochastic electrostatic potential. Both the weak and relatively strong turbulence regimes were analysed. The analysis of the diffusion coefficients in wave vector space provides an illustration of the fragmentation of drift wave structures in the radial direction and the generation of long-wavelength structures in the poloidal direction that are identified as zonal flows. We have shown that the fragmentation of drift wave structures is strongly influenced by the anisotropy parameter, the electrostatic Kubo number and by the initial values of the wave vector. © 2005 IOP Publishing Ltd., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2005

8. Intrinsic trapping of stochastic sheared magnetic field lines

Author

Negrea, Marian, Petrisor, Iulian, Balescu, Radu, Negrea, Marian, Petrisor, Iulian, and Balescu, Radu

Abstract

The properties of the magnetic lines of a shared stochastic magnetic field were discussed. The decorrelation trajectories for several values of the magnetic Kubo number and of the shear parameter were exhibited. It was found that the symmetry of the decorrelation trajectories appears in comparison with those obtained in electrostatic case. The diffusion coefficients for the magnetic field lines were also studied for both small and large Kubo-number regime., SCOPUS: ar.j, SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2004

9. A model for inductive plasma wind tunnels

Author

Degrez, Gérard, Deconinck, Herman, Fletcher, Douglas, Ern, Alexandre, Kolesnikov, Anatoly, Balescu, Radu, Louis, Yves, Carati, Daniele, Magin, Thierry, Degrez, Gérard, Deconinck, Herman, Fletcher, Douglas, Ern, Alexandre, Kolesnikov, Anatoly, Balescu, Radu, Louis, Yves, Carati, Daniele, and Magin, Thierry

Abstract

A numerical model for inductive plasma wind tunnels is developed. This model provides the flow conditions at the edge of a boundary layer in front of a thermal protection material placed in the plasma jet stream at the outlet of an inductive torch. The governing equations for the hydrodynamic field are derided from the kinetic theory. The electromagnetic field is deduced from the Maxwell equations. The transport properties of partially ionized and unmagnetized plasma in weak thermal nonequilibrium are derived from the Boltzmann equation. A kinetic data base of transport collision integrals is given for the Martian atmosphere. Multicomponent transport algorithms based upon Krylov subspaces are compared to mixture rules in terms of accuracy and computational cost. The composition and thermodynamic properties in local thermodynamicequilibrium are computed from the semi-classical statistical mechanics.The electromagnetic and hydrodynamic fields of an inductive wind tunnel is presented. A total pressure measurement technique is thoroughly investigated by means of numerical simulations., Doctorat en sciences appliquées, info:eu-repo/semantics/nonPublished

Published
2004

10. Lagrangian versus Eulerian correlations and transport scaling

Author

Vlad, Mǎdǎlina, Spineanu, F., Misguich, Jacques, Reuss, Jörg, Balescu, Radu, Itoh, Koichi, Itoh, S.-I., Vlad, Mǎdǎlina, Spineanu, F., Misguich, Jacques, Reuss, Jörg, Balescu, Radu, Itoh, Koichi, and Itoh, S.-I.

Abstract

SCOPUS: cp.j, info:eu-repo/semantics/published

Published
2004

11. Anomalous transport in plasmas

Author

Balescu, Radu, Vlad, Mǎdǎlina, Spineanu, Florin, Misguich, Jacques, Balescu, Radu, Vlad, Mǎdǎlina, Spineanu, Florin, and Misguich, Jacques

Abstract

The application of stochastic methods to the problem of particle and energy transport in turbulent plasmas is briefly reviewed. The "classical" Corrsin approximation is shown to be valid only in the limit of weak turbulence. The recently developed method of decorrelation trajectories is applicable over the whole range of turbulence intensities and yields the correct asymptotic behavior in the limit of very strong turbulence (subdiffusion). © 2004 Wiley Periodicals, Inc., SCOPUS: cp.j, FLWIN, info:eu-repo/semantics/published

Published
2004

12. Drift-wave turbulence and zonal flow generation

Author

Balescu, Radu and Balescu, Radu

Abstract

Liouville equation was used to analyze drift-wave turbulence in a plasma. The distribution function of wave packets characterized by position x and wave vector k was described. A closed kinetic equation for the ensemble-averaged part of the function has the form of a non-Markovian advection-diffusion equation, which described coupled diffusion processes in x and k spaces. Individual decorrelation trajectories analysis illustrated the generation of long wavelength structures in the poloidal direction that are identified as zonal flows., SCOPUS: ar.j, SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2003

14. Magnetic line trapping and effective transport in stochastic magnetic fields

Author

Vlad, Mǎdǎlina, Spineanu, F., Misguich, Jacques, Balescu, Radu, Vlad, Mǎdǎlina, Spineanu, F., Misguich, Jacques, and Balescu, Radu

Abstract

The transport of collisional particles in stochastic magnetic fields is studied using the decorrelation trajectory method. The nonlinear effect of magnetic line trapping is considered together with particle collisions. The running diffusion coefficient is determined for arbitrary values of the statistical parameters of the stochastic magnetic field and of the collisional velocity. The effect of the magnetic line trapping is determined. New anomalous diffusion regimes are found. © 2003 The American Physical Society., SCOPUS: ar.j, SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2003

17. Comment on 'diffusion in biased turbulence'

Author

Gleeson, James J.P., Vlad, Mǎdǎlina, Spineanu, Florin, Misguich, Jacques, Balescu, Radu, Gleeson, James J.P., Vlad, Mǎdǎlina, Spineanu, Florin, Misguich, Jacques, and Balescu, Radu

Abstract

SCOPUS: no.j, info:eu-repo/semantics/published

Published
2002

18. Noble Cantor sets acting as partial onternal transport barriers in fusion plasmas

Author

Misguich, J. H., Reuss, Jörg, Constantinescu, Dana, Steinbrecher, György, Vlad, Mǎdǎlina, Spineanu, F., Weyssow, Boris, Balescu, Radu, Misguich, J. H., Reuss, Jörg, Constantinescu, Dana, Steinbrecher, György, Vlad, Mǎdǎlina, Spineanu, F., Weyssow, Boris, and Balescu, Radu

Abstract

info:eu-repo/semantics/nonPublished

Published
2002

19. Noble Cantor sets acting as partial internal transport barriers in fusion plasmas

Author

Misguich, Jacques, Reuss, Jörg, Constantinescu, Dana, Steinbrecher, György, Vlad, Mǎdǎlina, Spineanu, F., Weyssow, Boris, Balescu, Radu, Misguich, Jacques, Reuss, Jörg, Constantinescu, Dana, Steinbrecher, György, Vlad, Mǎdǎlina, Spineanu, F., Weyssow, Boris, and Balescu, Radu

Abstract

SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2002

21. Reply to “Comment on ‘Diffusion in biased turbulence’ ”

Author

Vlad, Mǎdǎlina, Spineanu, Florin, Misguich, Jacques, Balescu, Radu, Vlad, Mǎdǎlina, Spineanu, Florin, Misguich, Jacques, and Balescu, Radu

Abstract

We agree with the results presented in the previous Comment [Phys. Rev. E 66, 038301 (2002)] concerning the equality, at any time moment, of the average Lagrangian and Eulerian velocities in two-dimensional incompressible stochastic velocity fields. We show that this statistical invariance is the effect of a complex nonlinear process that determines particle trapping and a compensatory acceleration of the nontrapped particles. We discuss the possibility of developing the decorrelation trajectory method which is able to describe the process of trapping but not the statistical acceleration. © 2002 The American Physical Society., SCOPUS: le.j, info:eu-repo/semantics/published

Published
2002

23. Diffusion in biased turbulence

Author

Vlad, Mǎdǎlina, Spineanu, Florin, Misguich, Jacques, Balescu, Radu, Vlad, Mǎdǎlina, Spineanu, Florin, Misguich, Jacques, and Balescu, Radu

Abstract

Analytical expressions were obtained for the Lagrangian velocity correlations and for the time-dependent diffusion coefficients of particle motion in divergence-free stochastic velocity fields with constant average Vd. The expressions were obtained by considering both the static and the time-dependent problems with the use of the decorrelation trajectory method., SCOPUS: ar.j, SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2001

34. Equilibrium statistical mechanics

Author

Balescu, Radu, Prigogine, Ilya, Balescu, Radu, and Prigogine, Ilya

Abstract

NOTXT, info:eu-repo/semantics/published

Published
2000

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