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  • 1
    Digitale Medien
    Digitale Medien
    Electron parametric instabilities of ultraintense laser pulses propagating in plasmas of arbitrary density (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3358-3368 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The dispersion relation for electron parametric instabilities of a circularly polarized laser wave of arbitrary intensity is established without restrictions on the plasma density. It is obtained in an implicit analytical form and solved numerically. The well-known stimulated Raman scattering, relativistic modulational instability, relativistic filamentation instability, and two-plasmon decay are recovered at low intensity. Their behavior in the ultrarelativistic regime is characterized by a wide extent of the unstable region in the wave vector space, with growth rates equal to a fraction of the laser frequency, and a strong harmonic generation. Particle-in-cell simulations confirm these results and show that the instability leads to a very strong heating of the plasma. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872494
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  • 2
    Digitale Medien
    Digitale Medien
    Theory and simulation of electronic relativistic parametric instabilities for ultraintense laser pulses propagating in hot plasmas (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 1664-1672 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The dispersion relation for electronic parametric instabilities of a circularly polarized laser wave is solved in the case where the distribution function is supposed to be cold in the transverse direction and to be a linear combination of a cold distribution function and of a Maxwellian in momentum in the longitudinal direction. Only densities below the critical density are considered. It is shown that the longitudinal temperature as expected reduces the growth rate, but that the existence of a hot tail is not sufficient to significantly reduce the instability. It is the bulk of the distribution function that must be heated to efficiently stabilize the system. Another important effect of the heating is to reduce the backscattered component of the instability. An example of a one-dimensional particle simulation performed in the exact conditions of validity of the theory is discussed. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1359744
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  • 3
    Digitale Medien
    Digitale Medien
    Modulational and Raman instabilities in the relativistic regime (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2807-2814 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A large amplitude electromagnetic wave propagating in a plasma is known to be subject to severe modulational and Raman instabilities. Previous works were devoted to the weakly relativistic limit and applied mainly to a cold underdense plasma. One extends these works to include the fully relativistic limit for a circularly polarized light for which one derives the dispersion relation in a one-dimensional plasma. The characteristics of the instabilities are also calculated in the case where the plasma is classically overdense, with 1〈(ωp/ω0)2〈γ, where ωp is the plasma frequency, ω0 is the laser frequency, and γ is the relativistic factor of an electron in the laser field. Particle-in-cell simulations confirm the results of the numerical solutions of the dispersion relation. For (ωp/ω0)2/γ=0.57 the growth rate can be as large as 0.52ω0. The nonlinear stage of the instability results in a strong heating of the electron distribution function. The theory is further extended to the case of an initially hot plasma, for which the dispersion relation of the instabilities is established. Its analytical solution is given in the case of a low density plasma. Particle-in-cell simulations are used to treat the general case. One observes a strong reduction of the growth rate of the instability, which tends to restore the possibility to propagate relativistic waves in plasmas. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871178
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  • 4
    Digitale Medien
    Digitale Medien
    Turbulent transport in mixed states of convective cells and sheared flows (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2912-2923 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Low-order mode coupling equations are used to describe recent computer simulations of resistive-g turbulent convection that show bifurcations for the onset of steady and pulsating sheared mass flows. The three convective transport states are identified with the tokamak confinement regimes called low-mode (L-mode), high-mode (H-mode), and edge-localized modes (ELMs). The first bifurcation (L→H) and the second bifurcation (H→ELMs) conditions are derived analytically and compared with direct solutions of the 6-ODE mode coupling equations. First an exact expression is given for the energy transfer rate from the fluctuations to the sheared mass flow through the triplet velocity correlation function. Then the time scale expansion required to derive the Markovian closure formula is given. Markovian closure formulas form the basis for the thermodynamic-like L–H models used in several recently proposed models. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871651
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  • 5
    Digitale Medien
    Digitale Medien
    Propagation of ultraintense laser pulses through overdense plasma layers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2693-2701 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Due to relativistic effects, a large amplitude electromagnetic wave can propagate in a classically overdense plasma with ω2p(approximately-greater-than)ω2(approximately-greater-than)ω2p/γ, where ωp is the plasma frequency, ω the laser frequency, and γ the relativistic factor of an electron in the laser field. Particle-in-cell simulations are used to study the interaction of an ultrahigh intensity laser pulse in normal incidence on a one-dimensional preformed plasma layer. Both electrons and ions dynamics are included. The width of the layer is 10 to 30 μm and the plasma is characterized by (ωp/ω)2=1.5. During the penetration of the electromagnetic wave a large longitudinal electric field is generated. It results in a strong longitudinal heating of electrons which reach relativistic temperatures. This heating further lowers the effective plasma frequency ωp/γ so the layer becomes almost transparent after the plasma crossing by the wave front. Velocity of the wave front, reflection and transmission rates are studied as functions of the incident energy flux, the plasma thickness, and the pulse duration. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871526
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  • 6
    Digitale Medien
    Digitale Medien
    Parametric instabilities due to relativistic electron mass variation (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 376-380 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The stability of an electronic plasma in a large-amplitude dipolar field is analyzed. In such a wave the relativistic electron mass variation must be taken into account and in an overdense plasma an instability arises. The corresponding weakly relativistic theory of Tsintsadze [Sov. Phys. JETP 32, 684 (1971)] is extended to the fully relativistic regime. The growth rate of the instability can attain a significant fraction of the dipolar field frequency. The relevance of this instability to the fast ignitor concept is discussed. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872719
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  • 7
    Digitale Medien
    Digitale Medien
    Particle diffusion in stochastic magnetic fields (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 711-721 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Particle transport across braided magnetic surfaces is studied by using simple field and collision models. Diffusion along and across field lines is taken into account. A general variational principle is established. It provides a useful guide for numerical computations. In a special case an explicit formula for the diffusion coefficient is obtained. Several diffusion regimes are clearly identified, and their domain of validity is determined. A new form of the diffusion coefficient has to be introduced in the long-mean-free-path regime.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.860961
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  • 8
    Digitale Medien
    Digitale Medien
    Suppression of sidebands by diffraction in a free-electron laser (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1721-1727 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The stability of sidebands in a free-electron laser is determined in the regime in which the three-dimensional structure of the modes is important. It is found that the growth rate of the sidebands in the presence of a fundamental mode that is weakly guided by the beam is reduced. The indications are that for some parameters the spatial growth rate of the sidebands can be made less than that of the fundamental.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.858951
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  • 9
    Digitale Medien
    Digitale Medien
    Numerical simulations of turbulent trapping in the weak beam–plasma instability (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 3129-3149 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Numerical simulations of the weak beam–plasma instability were done in the turbulent regime where small-scale trapping is a dominant feature of the instability, a regime with behavior not predicted by quasilinear theory. It occurs when the trapping frequency ν=(k2D)1/3 is larger than the growth rate γk of the instability. The results of the simulations were compared with those of a specific model of the turbulence, the so-called "turbulent trapping'' model, which gives precise formulas for the particle correlation functions, and predicts a growth rate well enhanced over the quasilinear value. It was found that the model gives accurate predictions for the correlation functions, and thus provides a good description of the turbulent structure of phase space. On the other hand, while growth rates were enhanced over the quasilinear values, the enhancements observed are smaller than expected from the quantitative predictions of the model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.866488
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  • 10
    Digitale Medien
    Digitale Medien
    Behavior of outer radiation zone and a new model of magnetospheric substorm
    Amsterdam : Elsevier
    Planetary and Space Science 20 (1972), S. 1391-1408 
    Details
    ISSN: 0032-0633
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/0032-0633(72)90047-5
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