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Mar 2007

Volume 14, Issue 3, Articles (03xxxx)

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Energetic protons generated by ultrahigh contrast laser pulses interacting with ultrathin targets

P. Antici, J. Fuchs, E. d’Humières, E. Lefebvre, M. Borghesi, E. Brambrink, C. A. Cecchetti, S. Gaillard, L. Romagnani, Y. Sentoku, T. Toncian, O. Willi, P. Audebert, and H. Pépin

Phys. Plasmas 14, 030701 (2007); http://dx.doi.org/10.1063/1.2480610 (4 pages) | Cited 21 times

Online Publication Date: 19 March 2007

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A regime of laser acceleration of protons, which relies on the interaction of ultrahigh contrast laser pulses with ultrathin targets, has been validated using experiments and simulations. Proton beams were accelerated to a maximum energy of ∼ 7.3 MeV from targets as thin as 30 nm irradiated at 1018 W cm−2 μm2 (1 J, 320 fs) with an estimated peak laser pulse to pedestal intensity contrast ratio of 1011. This represents nearly a tenfold increase in proton energy compared to the highest energies obtainable using non contrast enhanced pulses and thicker targets (>5 μm) at the same intensity. To obtain similar proton energy with thicker targets and the same laser pulse duration, a much higher laser intensity (i.e., above 1019 W cm−2 μm2) is required. The simulations are in close agreement with the experimental results, showing efficient electron heating compared to the case of thicker targets. Rapid target expansion, allowing laser absorption in density gradients, is key to enhanced electron heating and ion acceleration in ultrathin targets.
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52.38.Kd Laser-plasma acceleration of electrons and ions
52.38.Ph X-ray, γ-ray, and particle generation
52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.)
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
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back to top Basic Plasma Phenomena, Waves, Instabilities

Stimulated trapped electron acoustic wave scattering, electromagnetic soliton and ion vortices in intense laser interaction with subcritical plasmas

Baiwen Li, S. Ishiguro, M. M. Škorić, and T. Sato

Phys. Plasmas 14, 032101 (2007); http://dx.doi.org/10.1063/1.2436737 (5 pages) | Cited 2 times

Online Publication Date: 1 March 2007

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Stimulated trapped electron acoustic wave scattering by a linearly polarized intense laser in a subcritical plasma is studied by particle simulation. The scattering process is a three-wave parametric decay of the laser pump into a critical Stokes electromagnetic sideband wave and the trapped electron acoustic wave. As the ion acoustic wave grows in time, it breaks locally, followed by a large relativistic electromagnetic soliton. A new phenomenon, MeV ion vortex in ion phase space, forms by local electromagnetic and electrostatic fields inside the soliton. It is found that the electron acoustic wave mode is similar to the kinetic electrostatic electron nonlinear waves.
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52.38.Bv Rayleigh scattering; stimulated Brillouin and Raman scattering
52.35.Sb Solitons; BGK modes
52.35.We Plasma vorticity
52.65.Rr Particle-in-cell method
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

Enhancement of vacuum polarization effects in a plasma

A. Di Piazza, K. Z. Hatsagortsyan, and C. H. Keitel

Phys. Plasmas 14, 032102 (2007); http://dx.doi.org/10.1063/1.2646541 (13 pages) | Cited 10 times

Online Publication Date: 8 March 2007

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The dispersive effects of vacuum polarization on the propagation of a strong circularly polarized electromagnetic wave through a cold collisional plasma are studied analytically. It is found that, due to the singular dielectric features of the plasma, the vacuum effects on the wave propagation in a plasma are qualitatively different and much larger than those in pure vacuum in the regime when the frequency of the propagating wave approaches the plasma frequency. A possible experimental setup to detect these effects in plasma is described.
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.25.Mq Dielectric properties
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

How really transverse is the filamentation instability?

A. Bret, L. Gremillet, and J. C. Bellido

Phys. Plasmas 14, 032103 (2007); http://dx.doi.org/10.1063/1.2710810 (6 pages) | Cited 20 times

Online Publication Date: 19 March 2007

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It is generally considered that the linear filamentation instability encountered when two counter streaming electron beams interpenetrate is purely transverse. Exact and approximated results are derived in the relativistic fluid approximation showing that within some parameter range, filamentation can be indeed almost longitudinal with cos(math)≲1−3.1/γb, where γb is the relativistic factor of the beam. Temperature effects are then evaluated through relativistic kinetic theory and yield even fewer transverse filamentation modes. In the cold case, the transverse approximation overestimates the growth rate by a factor ∝math.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.40.Mj Particle beam interactions in plasmas
52.27.Ny Relativistic plasmas
52.25.Dg Plasma kinetic equations

Ion heating in the presheath

Albert Meige, Orson Sutherland, Helen B. Smith, and Rod W. Boswell

Phys. Plasmas 14, 032104 (2007); http://dx.doi.org/10.1063/1.2709648 (7 pages) | Cited 4 times

Online Publication Date: 19 March 2007

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A one-dimensional model of a small plasma ion source (10 cm long) is studied. A hybrid simulation where ions are treated as particles and electrons as a fluid obeying the Boltzmann relation is used to investigate ion heating in the plasma presheath. At low pressure (below a few mTorr), the ion velocity distribution is Maxwellian in the bulk and becomes a drifting Maxwellian distribution while transiting the presheath. The distribution remains essentially isotropic as the ions are accelerated through the presheath to satisfy the Bohm criterion. At intermediate pressures (around 10 mTorr), ion-neutral collisions scatter a significant part of the ion kinetic energy from the parallel direction to the perpendicular direction, leading to a net heating of the ions. In addition, the ion velocity distribution becomes distinctly anisotropic. At higher pressure (above a few tens of mTorr), ion heating is still observed, but yields isotropic ion velocity distributions.
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52.50.Gj Plasma heating by particle beams
52.40.Kh Plasma sheaths
52.50.Dg Plasma sources
52.65.Ww Hybrid methods
52.25.Fi Transport properties
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

Kinetic Alfvén waves in a homogeneous dusty magnetoplasma with dust charge fluctuation effects

K. Zubia, N. Rubab, H. A. Shah, M. Salimullah, and G. Murtaza

Phys. Plasmas 14, 032105 (2007); http://dx.doi.org/10.1063/1.2710457 (6 pages) | Cited 8 times

Online Publication Date: 23 March 2007

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Kinetic Alfvén waves with finite Larmor radius effects have been examined rigorously in a uniform dusty plasma in the presence of an external/ambient magnetic field. Two-potential theory has been applied for these electromagnetic waves and the dispersion relation is derived which shows a cutoff frequency at the dust-lower-hybrid frequency due to the hybrid motion of magnetized ions and cold and unmagnetized dust dynamics. The dust charge fluctuation effect was analyzed for finding the damping of the electromagnetic kinetic Alfvén waves, which arises on account of the electrostatic parallel component of the waves. The dust charge fluctuation damping is seen to be contributed dominantly by the perpendicular motion of electrons and ions in the dusty magnetoplasma.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.27.Lw Dusty or complex plasmas; plasma crystals
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.25.Gj Fluctuation and chaos phenomena
52.25.Fi Transport properties
52.25.Xz Magnetized plasmas

Gas acoustic and ion acoustic waves in partially ionized plasmas with magnetized electrons

J. Vranjes, B. P. Pandey, and S. Poedts

Phys. Plasmas 14, 032106 (2007); http://dx.doi.org/10.1063/1.2710796 (7 pages) | Cited 4 times

Online Publication Date: 23 March 2007

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The properties of gas acoustic and ion acoustic modes are investigated in a collisional, weakly ionized plasma in the presence of unmagnetized ions and magnetized electrons. In such a plasma, an ion acoustic mode, driven by an electron flow along the magnetic field lines, can propagate almost at any angle with respect to the ambient field lines as long as the electrons are capable of participating in the perturbations by moving only along the field lines. Several effects, including the electron-ion collisions, the perturbations of the neutral gas, and the electromagnetic perturbations, are studied in the present work. The electron-ion collisions are shown to modify the previously obtained angle-dependent instability threshold for the driving electron flow. The inclusion of the neutral dynamics implies an additional neutral sound mode, which couples to the current driven ion acoustic mode, and these two modes can interchange their identities in certain parameter regimes. The electromagnetic effects, which in the present model imply a bending of the magnetic field lines, result in a further destabilization of an already unstable ion acoustic wave. The applicability of these results to the solar and/or space and laboratory plasmas is discussed.
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52.35.Dm Sound waves
52.30.Ex Two-fluid and multi-fluid plasmas
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.25.Xz Magnetized plasmas

Finite amplitude envelope solitons in a pair-ion plasma

W. M. Moslem, I. Kourakis, and P. K. Shukla

Phys. Plasmas 14, 032107 (2007); http://dx.doi.org/10.1063/1.2710455 (6 pages) | Cited 8 times

Online Publication Date: 28 March 2007

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See Also: Erratum

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The nonlinear coupling between finite amplitude ion thermal waves (ITWs) and quasistationary density perturbations in a pair-ion plasma is considered. A generalized nonlinear Schrödinger equation is derived for the ITW electric field envelope, accounting for large amplitude quasistationary plasma slow motion describing the ITW ponderomotive force. The present theory accounts for the trapping of ITWs in a large amplitude ion density hole. The small amplitude limit is considered and exact analytical solutions are obtained. Finite amplitude solutions are obtained numerically and their characteristics are discussed.
Show PACS
52.35.Sb Solitons; BGK modes
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.25.Fi Transport properties
52.25.Dg Plasma kinetic equations
52.27.Aj Single-component, electron-positive-ion plasmas
02.60.Lj Ordinary and partial differential equations; boundary value problems

Criterion for bulk behavior of a Yukawa disk

T. E. Sheridan

Phys. Plasmas 14, 032108 (2007); http://dx.doi.org/10.1063/1.2713722 (6 pages) | Cited 8 times

Online Publication Date: 28 March 2007

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A Yukawa disk is a two-dimensional system of n particles interacting through a Yukawa potential (i.e., a screened Coulomb or Debye potential) with Debye length λ and confined in an isotropic parabolic well where the single-particle oscillation frequency is ω0. One example of a Yukawa disk is a two-dimensional complex (dusty) plasma. The emergence of bulk (macroscopic) behavior in a strongly coupled Yukawa disk is studied by considering the dependence of the normalized, squared breathing frequency ωbr2/ω02 (i.e., the bulk modulus) on n, λ, the disk radius R0, and the nearest-neighbor distance a. An analytical expression for ωbr2/ω02 is derived for the bulk limit, R0≫λ, with a/λ finite. In the plasma regime a≲λ, so that each particle interacts with many other particles, ωbr2/ω02 ≈ 4 independent of a/λ. In the nearest-neighbor regime a≳λ, short-range interactions dominate and ωbr2/ω02 ∼ a/λ. Computational solutions of the model for n = 100−3200 particles approach the theoretical bulk limit as n increases. Solutions with n = 3200 and a/λ between 0.25 and 0.5 are found to give the best approximation to an unbounded plasma.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.27.Gr Strongly-coupled plasmas
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

Stimulated forward Raman scattering of a laser in a magnetized plasma

Vivek Sajal, Deepak Dahiya, and V. K. Tripathi

Phys. Plasmas 14, 032109 (2007); http://dx.doi.org/10.1063/1.2714499 (5 pages) | Cited 1 time

Online Publication Date: 28 March 2007

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A Gaussian laser beam propagating through a low-density plasma in the presence of an azimuthal magnetic field undergoes stimulated forward Raman scattering producing a lower hybrid wave and two radially localized electromagnetic sideband waves. The radial widths of the sidebands are of the order of the spot size of the pump, whereas the radial width of the lower hybrid wave depends on the growth rate of the Raman process. The nonlocal effect arising, due to the azimuthal magnetic field, reduces the region of nonlocal interaction and hence the growth rate. The growth rate of stimulated Raman forward scattering first increases on increasing magnetic field, maximizes at some optimum value of magnetic field, and then decreases.
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52.38.Bv Rayleigh scattering; stimulated Brillouin and Raman scattering
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Xz Magnetized plasmas
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)

Effect of self-gravitation and dust-charge fluctuations on the shielding and energy loss of N×M projectiles in a collisional dusty plasma

M. Adnan Sarwar and Arshad M. Mirza

Phys. Plasmas 14, 032110 (2007); http://dx.doi.org/10.1063/1.2714501 (7 pages)

Online Publication Date: 29 March 2007

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A simple derivation of the electrostatic potential and energy loss of N×M test charge projectiles traveling through dusty plasma has been presented. The effect of dust-charge fluctuations, dust neutral collisions, and self-gravitation on the shielded potential and energy loss of charge projectiles has been investigated both analytically as well as numerically. An interference contribution of these projectiles to the shielded potential and energy loss has been observed, which depends upon their relative orientation and separation distance. A comparison has been made for correlated and uncorrelated motion of the two projectiles. The amplitude of the shielded potential is enhanced with the increase of dust Jeans frequency for separation less than the effective Debye length. The dust-charge fluctuations produce a potential well for a slow charge relaxation rate and energy is gained, not lost, by the test charge projectiles. However, a fast charge relaxation rate with a fixed value of Jeans frequency enhances the energy loss. The dust neutral collisions are also found to enhance the energy loss for the test charge velocities greater than the dust acoustic speeds. The present investigation might be useful to explain the coagulation of dust particles such as those in molecular clouds, the interstellar medium, comet tails, planetary rings, etc.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.25.Gj Fluctuation and chaos phenomena
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.20.Fs Electron collisions
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.25.Fi Transport properties

Finite Larmor radius magnetohydrodynamic analysis of the Rayleigh-Taylor instability in Z pinches with sheared axial flow

X. M. Qiu, L. Huang, and G. D. Jian

Phys. Plasmas 14, 032111 (2007); http://dx.doi.org/10.1063/1.2717583 (8 pages) | Cited 2 times

Online Publication Date: 29 March 2007

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The Rayleigh-Taylor (RT) instability in Z pinches with sheared axial flow (SAF) is analyzed using finite Larmor radius (FLR) magnetohydrodynamic theory, in whose momentum equation the FLR effect (also referred to as the effect of gyroviscosity) is introduced through an anisotropic ion (FLR) stress tensor. A dispersion relation is derived for the linear RT instability. Both analytical and numerical solutions of the dispersion equation are given. The results indicate that the short-wavelength modes of the RT instability can be stabilized by a sufficient FLR, whereas the long-wavelength modes can be stabilized by a sufficient SAF. In the small-wavenumber region, for normalized wavenumber K<2.4, the hybrid RT/KH (Kelvin-Helmholtz) instability is shown to be the most difficult to stabilize. However the synergistic effect of the SAF and gyroviscosity can mitigate both the RT instability in the large-wavenumber region (K>2.4) and the hybrid RT/KH instability in the small-wavenumber region. In addition, this synergistic effect can compress the RT instability to a narrow wavenumber region. Even the thorough stabilization of the RT instability in the large-wavenumber region is possible with a sufficient SAF and a sufficient gyroviscosity.
Show PACS
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.25.Fi Transport properties
52.25.Dg Plasma kinetic equations

Landau damping of dust acoustic waves in a Lorentzian plasma

Myoung-Jae Lee

Phys. Plasmas 14, 032112 (2007); http://dx.doi.org/10.1063/1.2716661 (5 pages) | Cited 19 times

Online Publication Date: 30 March 2007

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The Landau damping of dust acoustic waves propagating in a dusty plasma modeled by a Lorentzian (kappa) distribution for electrons and ions, and by a Maxwellian distribution for the dust grains is kinetically investigated. The dust acoustic waves are found in the range of kvd≪ω≪kvi≪kve, where vα is the thermal velocity of species α( = i,e,d). The damping rate is shown to be dependent on the spectral index κ as well as the ratio of ion density to electron. The maximum Landau damping rate is derived and found to be approximately 0.2σκωpd where ωpd is the dust plasma frequency and σκ is a κ-dependent factor, which has the maximum value of 1.33 (for the smallest κ) and reduces to unity as the nonthermal effect disappears.
Show PACS
52.27.Lw Dusty or complex plasmas; plasma crystals
52.35.Dm Sound waves
52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

Nonlinear regime of the filamentation of a microwave produced plasma

B. Shokri and A. R. Niknam

Phys. Plasmas 14, 032113 (2007); http://dx.doi.org/10.1063/1.2717893 (5 pages) | Cited 1 time

Online Publication Date: 30 March 2007

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The nonlinear dynamics of the magnetic field and anisotropic instability due to interaction of a plasma with microwave radiation, by making use of magnetohydrodynamic equations and Ampere-Maxwell law, are investigated. Also, it is shown that the Lienard nonlinear differential equation describes the evolution of the magnetic field in the plasma. We investigate the profiles of magnetic field and electron density variation in plasma and show that these profiles have a nonsinusoidal shape in the nonlinear regime. Furthermore, it is shown that the electron density becomes highly peaked in this regime. Also, due to the nonlinear effect, the cross section and shape of transverse filamentation can vary in the static limit.
Show PACS
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
02.30.Hq Ordinary differential equations
back to top Nonlinear Phenomena, Turbulence, Transport

The impact of small-scale turbulence on laminar magnetic reconnection

P. G. Watson, S. Oughton, and I. J. D. Craig

Phys. Plasmas 14, 032301 (2007); http://dx.doi.org/10.1063/1.2458595 (11 pages) | Cited 3 times

Online Publication Date: 2 March 2007

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Initial states in incompressible two-dimensional magnetohydrodynamics that are known to lead to strong current sheets and (laminar) magnetic reconnection are modified by the addition of small-scale turbulent perturbations of various energies. The evolution of these states is computed with the aim of ascertaining the influence of the turbulence on the underlying laminar solution. Two main questions are addressed here: (1) What effect does small-scale turbulence have on the energy dissipation rate of the underlying solution? (2) What is the threshold turbulent perturbation level above which the original laminar reconnective dynamics is no longer recognizable. The simulations show that while the laminar dynamics persist the dissipation rates are largely unaffected by the turbulence, other than modest increases attributable to the additional small length scales present in the new initial condition. The solutions themselves are also remarkably insensitive to small-scale turbulent perturbations unless the perturbations are large enough to undermine the integrity of the underlying cellular flow pattern. Indeed, even initial states that lead to the evolution of small-scale microscopic sheets can survive the addition of modest turbulence. The role of a large-scale organizing background magnetic field is also addressed.
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52.35.Ra Plasma turbulence
52.35.Vd Magnetic reconnection
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.25.Fi Transport properties
52.65.Kj Magnetohydrodynamic and fluid equation

Collisional damping for ion temperature gradient mode driven zonal flow

Yong Xiao, Peter J. Catto, and Kim Molvig

Phys. Plasmas 14, 032302 (2007); http://dx.doi.org/10.1063/1.2536297 (11 pages) | Cited 12 times

Online Publication Date: 2 March 2007

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Zonal flow helps reduce and control the level of ion temperature gradient turbulence in a tokamak. The collisional damping of zonal flow has been estimated by Hinton and Rosenbluth (HR) in the large radial wavelength limit. Their calculation shows that the damping of zonal flow is closely related to the frequency response of neoclassical polarization of the plasma. Based on a variational principle, HR calculated the neoclassical polarization in the low and high collisionality limits. A new approach, based on an eigenfunction expansion of the collision operator, is employed to evaluate the neoclassical polarization and the zonal flow residual for arbitrary collisionality. An analytical expression for the temporal behavior of the zonal flow is also given showing that the damping rate tends to be somewhat slower than previously thought. These results are expected to be useful extensions of the original HR collisional work that can provide an effective benchmark for numerical codes for all regimes of collisionality.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.35.Ra Plasma turbulence
52.55.Fa Tokamaks, spherical tokamaks
52.25.Fi Transport properties

On the kinetic stability of magnetic structures in electron drift turbulence

Martin Jucker and Vladimir P. Pavlenko

Phys. Plasmas 14, 032303 (2007); http://dx.doi.org/10.1063/1.2646436 (5 pages) | Cited 5 times

Online Publication Date: 2 March 2007

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The generation of large-scale magnetic fields in magnetic electron drift mode turbulence is investigated. The mechanism of magnetic Reynolds stress is elucidated with the help of kinetic theory, and a sufficient criterion in the form of Nyquist’s criterion for the generation of zonal magnetic fields is developed. This criterion is then applied to a narrow wave packet, where an amplitude threshold due to finite width of the wave spectrum in k space is found.
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52.35.Kt Drift waves
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Ra Plasma turbulence

Nonlinear dust acoustic waves in a nonuniform magnetized complex plasma with nonthermal ions and dust charge variation

W. F. El-Taibany, Miki Wadati, and R. Sabry

Phys. Plasmas 14, 032304 (2007); http://dx.doi.org/10.1063/1.2646587 (11 pages) | Cited 24 times

Online Publication Date: 2 March 2007

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Propagations of nonlinear dust acoustic (DA) solitary waves and shock waves in a nonuniform magnetized dusty plasma are investigated. The incorporation of the combined effects of nonthermally distributed ions, nonadiabatic dust charge fluctuation, and the inhomogeneity caused by nonuniform equilibrium values of particle density, charging variable, and particle potential on the waves leads to a significant modification to the nature of nonlinear DA solitary waves. The nonlinear wave evolution is governed by a modified Zakhavov-Kusnetsov-Burgers (MZKB) equation, whose coefficients are space dependent. Using a generalized expansion method, new solutions for the MZKB equation are obtained. The form of solutions consists of two parts; one of them is the amplitude factor and the other is a superposition of bell-shaped and kink-type shock waves. New solutions are classified into three categories. A type of the solution is determined depending on the nonthermal parameter. Findings in this investigation should be useful for understanding the ion acceleration mechanisms close to the Moon and also enhancing our knowledge on pickup ions around unmagnetized bodies, such as comets, Mars, and Venus, including medium inhomogeneities with nonadiabatic dust charging processes.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Sb Solitons; BGK modes
52.35.Tc Shock waves and discontinuities
52.25.Gj Fluctuation and chaos phenomena
52.25.Xz Magnetized plasmas

Small-scale drift-Alfven wave driven zonal flows in plasmas

T. D. Kaladze, D. J. Wu, and L. Yang

Phys. Plasmas 14, 032305 (2007); http://dx.doi.org/10.1063/1.2709658 (8 pages) | Cited 5 times

Online Publication Date: 5 March 2007

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The problem of generation of zonal flows by small-scale drift-Alfven waves is illuminated more completely. The growth rate of zonal-flow instabilities much greater than known by previous investigations is obtained. Dependence of the growth rate on the spectrum purity of the wave packet is also investigated. It is shown that the sufficient broadening of the wave packet gives resonant-type instability with the growth rate of the order of hydrodynamic one. The appropriate conditions for instabilities are determined.
Show PACS
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Kt Drift waves
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

Statistical analysis of fluctuations and noise-driven transport in particle-in-cell simulations of plasma turbulence

I. Holod and Z. Lin

Phys. Plasmas 14, 032306 (2007); http://dx.doi.org/10.1063/1.2673002 (6 pages) | Cited 16 times

Online Publication Date: 6 March 2007

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The problem of discrete particle noise has been studied based on direct fluctuation measurements from gyrokinetic particle-in-cell simulations of stable plasmas. From the statistical analysis of electrostatic potential time evolution, the space-time correlation function has been measured. Fluctuation spectra have been constructed and analyzed in detail. Noise-driven transport is calculated using the quasilinear expression for the diffusion coefficient and the obtained noise spectrum. The theoretical value of electron heat conductivity shows good agreement with that measured in the simulation. It has been shown that for the realistic parameters in actual turbulence simulations, the noise-driven transport depends linearly on the entropy of the system. This study makes it possible to estimate and subtract the noise contribution to the total transport during turbulence simulations.
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52.35.Ra Plasma turbulence
52.25.Gj Fluctuation and chaos phenomena
52.25.Fi Transport properties
52.65.Rr Particle-in-cell method
52.25.Dg Plasma kinetic equations
52.25.Kn Thermodynamics of plasmas

Fluctuations and discrete particle noise in gyrokinetic simulation of drift waves

Thomas G. Jenkins and W. W. Lee

Phys. Plasmas 14, 032307 (2007); http://dx.doi.org/10.1063/1.2710808 (10 pages) | Cited 4 times

Online Publication Date: 20 March 2007

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The relevance of the gyrokinetic fluctuation-dissipation theorem (FDT) to thermal equilibrium and nonequilibrium states of the gyrokinetic plasma is explored, with particular focus being given to the contribution of weakly damped normal modes to the fluctuation spectrum. It is found that the fluctuation energy carried in the normal modes exhibits the proper scaling with particle count (as predicted by the FDT in thermal equilibrium) even in the presence of drift waves, which grow linearly and attain a nonlinearly saturated steady state. This favorable scaling is preserved, and the saturation amplitude of the drift wave unaffected, for parameter regimes in which the normal modes become strongly damped and introduce a broad spectrum of discreteness-induced background noise in frequency space.
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52.25.Gj Fluctuation and chaos phenomena
52.35.Kt Drift waves
52.65.Tt Gyrofluid and gyrokinetic simulations
52.25.Dg Plasma kinetic equations
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)

Saturation of a tearing mode in zero-β full magnetohydrodynamics

N. Arcis, D. F. Escande, and M. Ottaviani

Phys. Plasmas 14, 032308 (2007); http://dx.doi.org/10.1063/1.2710799 (6 pages) | Cited 11 times

Online Publication Date: 23 March 2007

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Within the cylindrical approximation, the nonlinear saturation of a tearing mode island in the full magnetohydrodynamics (MHD) model with no pressure and a uniform resistivity profile is described using a recent perturbation method based on the technique of matched asymptotic expansion, where the perturbation parameter is the island width ws. The matching condition provides the saturation equation for ws that is given to the adequate order and does not depend on the normalization length. This enables to prove that the errors due to reduced MHD (RMHD) are negligible in the calculation of tearing mode saturation in the tokamak. It also provides a way to benchmark MHD numerical simulations of magnetic self-reversal for the reversed-field pinch where RMHD does not apply.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.25.Fi Transport properties
52.55.Fa Tokamaks, spherical tokamaks
52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps
back to top Magnetically Confined Plasmas, Heating, Confinement

Mach probe interpretation in the presence of suprathermal electrons

J. P. Gunn and V. Fuchs

Phys. Plasmas 14, 032501 (2007); http://dx.doi.org/10.1063/1.2672896 (13 pages) | Cited 6 times

Online Publication Date: 2 March 2007

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The collisionless theory of Mach probes assuming isothermal, Maxwellian electrons is extended to include an isotropic, two-temperature electron distribution function. The kinetic equations for ion and electron motion in the probe wake are solved using a quasineutral particle-in-cell method, which compares qualitatively well with the results of a simple fluid model. The measured Mach number decreases slightly with increasing hot electron concentration, but the main effect is on the measured electron temperature. Due to the fact that the probe is sensitive to even a tiny population of hot electrons, the resulting ion sound speed can be overestimated by up to a factor of 2, leading to measurements of absolute flow speed that are too large.
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52.30.-q Plasma dynamics and flow
52.65.-y Plasma simulation
52.70.-m Plasma diagnostic techniques and instrumentation
back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

The influence of target irradiation conditions on the parameters of laser-produced plasma jets

A. Kasperczuk, T. Pisarczyk, S. Borodziuk, J. Ullschmied, E. Krousky, K. Masek, M. Pfeifer, K. Rohlena, J. Skala, and P. Pisarczyk

Phys. Plasmas 14, 032701 (2007); http://dx.doi.org/10.1063/1.2715560 (4 pages) | Cited 6 times

Online Publication Date: 28 March 2007

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Recent experimental results demonstrate that the forming of plasma jets is a fundamental process accompanying the laser-produced plasma expansion, if a massive planar target with relatively high atomic number is irradiated by a defocused laser beam. In this paper some new results on the influence of target irradiation conditions on plasma jet parameters are presented. The experiment was carried out at the Prague Asterix Laser System (PALS) iodine laser [ K. Jungwirth, A. Cejnarova, L. Juha, B. Kralikova, J. Krasa, E. Krousky, P. Krupickova, L. Laska, K. Masek, A. Prag, O. Renner, K. Rohlena, B. Rus, J. Skala, P. Straka, and J. Ullschmied, Phys. Plasmas 8, 2495 (2001) ]. with the third harmonic beam of the pulse duration of 250 ps. The beam energies varied in the range of 13–160 J. The planar massive targets used in the experiment were made of copper. For measurements of the electron density evolution a three frame interferometric system was employed. The jets were produced in the whole range of the laser energy used. Calculations of the efficiency of the plasma jet production show that it decreases with increasing the laser energy.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Measurements of the effects of the intensity pickets on laser imprinting for direct-drive, adiabat-shaping designs on OMEGA

V. A. Smalyuk, V. N. Goncharov, K. S. Anderson, R. Betti, R. S. Craxton, J. A. Delettrez, D. D. Meyerhofer, S. P. Regan, and T. C. Sangster

Phys. Plasmas 14, 032702 (2007); http://dx.doi.org/10.1063/1.2715550 (4 pages) | Cited 3 times

Online Publication Date: 29 March 2007

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Effects of the intensity pickets on laser imprinting were investigated using laser-driven, planar plastic and foam targets on the OMEGA laser system [ T. R. Boehly et al., Opt. Commun. 133, 495 (1997) ]. Intensity pickets are used in adiabat-shaping techniques designed to improve stability of inertial confinement fusion targets. The measurements were performed in planar foam targets using the decaying shock method of adiabat shaping and in planar plastic targets using the relaxation (RX) method. In foam targets, the picket reduced the target areal-density modulations by ∼ 6 times at shorter spatial wavelengths of 30 and 60 μm, while at a longer wavelength of 120 μm there was no reduction. The “imprint efficiency,” the equivalent surface amplitude produced by imprinting, was reduced by the intensity picket by a factor of ∼ 3 at a spatial wavelength of 60 μm, while it was increased by a factor of ∼ 2 at a 120-μm spatial wavelength. In plastic targets, used to test the RX method, the imprint efficiency was reduced by the intensity picket by a factor of ∼ 2 at spatial wavelengths of 30 and 60 μm, while it was about the same at a 120-μm spatial wavelength.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.57.Fg Implosion symmetry and hydrodynamic instability (Rayleigh-Taylor, Richtmyer-Meshkov, imprint, etc.)
52.35.Tc Shock waves and discontinuities
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
28.52.Cx Fueling, heating and ignition
28.52.Av Theory, design, and computerized simulation
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