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Apr 2009

Volume 16, Issue 4, Articles (04xxxx)

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Phys. Plasmas 16, 041004 (2009); http://dx.doi.org/10.1063/1.3101816 (5 pages)

R. P. Drake, C. C. Kuranz, A. R. Miles, H. J. Muthsam, and T. Plewa
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Anomalous energy dissipation of electron current pulses propagating through an inhomogeneous collisionless plasma medium

Sharad Kumar Yadav, Amita Das, Predhiman Kaw, and Sudip Sengupta

Phys. Plasmas 16, 040701 (2009); http://dx.doi.org/10.1063/1.3122939 (4 pages) | Cited 9 times

Online Publication Date: 20 April 2009

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The evolution of fast rising electron current pulses propagating through an inhomogeneous plasma has been studied through electron magnetohydrodynamic fluid simulations. A novel process of anomalous energy dissipation and stopping of the electron pulse in the presence of plasma density inhomogeneity is demonstrated. The electron current essentially dissipates its energy through the process of electromagnetic shock formation in the presence of density inhomogeneity. A direct relevance of this rapid energy dissipation process to the fast ignition concept of laser fusion is shown.
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52.40.-w Plasma interactions (nonlaser)
52.65.Kj Magnetohydrodynamic and fluid equation
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Tc Shock waves and discontinuities
52.57.-z Laser inertial confinement

On the physical interpretation of Malyshkin’s (2008) model of resistive Hall magnetohydrodynamic reconnection

Dmitri A. Uzdensky

Phys. Plasmas 16, 040702 (2009); http://dx.doi.org/10.1063/1.3125819 (2 pages) | Cited 5 times

Online Publication Date: 27 April 2009

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A simple Sweet–Parker-like model for the electron current layer in resistive Hall magnetohydrodynamic reconnection is presented, with the focus on the small-resistivity limit. The derivation readily recovers the main results obtained recently by Malyshkin [Phys. Rev. Lett. 101, 225001 (2008) ], but is much quicker and more physically transparent. In particular, it highlights the role of resistive drag in determining the electron outflow velocity. The principal limitations of any such approach are discussed.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.30.Ex Two-fluid and multi-fluid plasmas
52.35.Vd Magnetic reconnection
94.30.cp Magnetic reconnection
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Preface to Special Topic: High Energy Density Laboratory Astrophysics: Summaries of Papers Given During a Special Session at the American Physical Society 2008 April Meeting, St. Louis, Missouri

Bruce A. Remington

Phys. Plasmas 16, 040901 (2009); http://dx.doi.org/10.1063/1.3117362 (2 pages)

Online Publication Date: 22 April 2009

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Abstract Unavailable
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95.30.Cq Elementary particle processes
95.30.Qd Magnetohydrodynamics and plasmas

Accretion disk dynamics, photoionized plasmas, and stellar opacities

R. C. Mancini, J. E. Bailey, J. F. Hawley, T. Kallman, M. Witthoeft, S. J. Rose, and H. Takabe

Phys. Plasmas 16, 041001 (2009); http://dx.doi.org/10.1063/1.3101819 (11 pages) | Cited 7 times

Online Publication Date: 22 April 2009

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We present a brief review on the atomic kinetics, modeling and interpretation of astrophysical observations, and laboratory astrophysics experiments. The emphasis is on benchmarking of opacity calculations relevant for solar structure models, photoionized plasmas research, the magnetohydrodynamic numerical simulation of accretion disk dynamics, and a connection between radiation transport effects and plasma source geometry details. Specific cases of application are discussed with relevance to recent and proposed laboratory astrophysics experiments as well as Chandra and X-ray Multi-Mirror Mission Newton observations.
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97.10.Ex Stellar atmospheres (photospheres, chromospheres, coronae, magnetospheres); radiative transfer; opacity and line formation
97.10.Cv Stellar structure, interiors, evolution, nucleosynthesis, ages
96.50.Tf MHD waves; plasma waves, turbulence
95.30.Qd Magnetohydrodynamics and plasmas
52.65.Kj Magnetohydrodynamic and fluid equation
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

Intense laser-plasma interactions: New frontiers in high energy density physics

P. A. Norreys, F. N. Beg, Y. Sentoku, L. O. Silva, R. A. Smith, and R. M. G. M. Trines

Phys. Plasmas 16, 041002 (2009); http://dx.doi.org/10.1063/1.3101813 (15 pages) | Cited 20 times

Online Publication Date: 22 April 2009

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A review is presented here of a number of invited papers presented at the 2008 American Physical Society April meeting [held jointly with High Energy Density Physics/High Energy Density Laboratory Astrophysics (HEDP/HEDLA) Conference] devoted to intense laser-matter interactions. They include new insights gained from wave-kinetic theory into laser-wakefield accelerators and drift wave turbulence interacting with zonal flows in magnetized plasmas; interactions with cluster media for the generation of radiative blast waves; fast electron energy transport in cone-wire targets; numerical investigations into Weibel instability in electron-positron-ion plasmas and the generation of gigabar pressures with thin foil interactions.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.35.Kt Drift waves
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.35.Ra Plasma turbulence

Frontiers of the physics of dense plasmas and planetary interiors: Experiments, theory, and applications

J. J. Fortney, S. H. Glenzer, M. Koenig, B. Militzer, D. Saumon, and D. Valencia

Phys. Plasmas 16, 041003 (2009); http://dx.doi.org/10.1063/1.3101818 (7 pages) | Cited 13 times

Online Publication Date: 22 April 2009

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Recent developments of dynamic x-ray characterization experiments of dense matter are reviewed, with particular emphasis on conditions relevant to interiors of terrestrial and gas giant planets. These studies include characterization of compressed states of matter in light elements by x-ray scattering and imaging of shocked iron by radiography. Several applications of this work are examined. These include the structure of massive “super-Earth” terrestrial planets around other stars, the 40 known extrasolar gas giants with measured masses and radii, and Jupiter itself, which serves as the benchmark for giant planets.
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95.30.Qd Magnetohydrodynamics and plasmas
97.82.-j Extrasolar planetary systems
52.70.La X-ray and γ-ray measurements
95.85.Nv X-ray
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Stellar explosions, instabilities, and turbulence

R. P. Drake, C. C. Kuranz, A. R. Miles, H. J. Muthsam, and T. Plewa

Phys. Plasmas 16, 041004 (2009); http://dx.doi.org/10.1063/1.3101816 (5 pages) | Cited 2 times

Online Publication Date: 22 April 2009

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It has become very clear that the evolution of structure during supernovae is centrally dependent on the pre-existing structure in the star. Modeling of the pre-existing structure has advanced significantly, leading to improved understanding and to a physically based assessment of the structure that will be present when a star explodes. It remains an open question whether low-mode asymmetries in the explosion process can produce the observed effects or whether the explosion mechanism somehow produces jets of material. In any event, the workhorse processes that produce structure in an exploding star are blast-wave driven instabilities. Laboratory experiments have explored these blast-wave-driven instabilities and specifically their dependence on initial conditions. Theoretical work has shown that the relative importance of Richtmyer–Meshkov and Rayleigh–Taylor instabilities varies with the initial conditions and does so in ways that can make sense of a range of astrophysical observations.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
95.30.Lz Hydrodynamics
97.60.Bw Supernovae

Astrophysical jets: Observations, numerical simulations, and laboratory experiments

P. M. Bellan, M. Livio, Y. Kato, S. V. Lebedev, T. P. Ray, A. Ferrari, P. Hartigan, A. Frank, J. M. Foster, and P. Nicolaï

Phys. Plasmas 16, 041005 (2009); http://dx.doi.org/10.1063/1.3101812 (8 pages) | Cited 9 times

Online Publication Date: 22 April 2009

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This paper provides summaries of ten talks on astrophysical jets given at the HEDP/HEDLA-08 International Conference in St. Louis. The talks are topically divided into the areas of observation, numerical modeling, and laboratory experiment. One essential feature of jets, namely, their filamentary (i.e., collimated) nature, can be reproduced in both numerical models and laboratory experiments. Another essential feature of jets, their scalability, is evident from the large number of astrophysical situations where jets occur. This scalability is the reason why laboratory experiments simulating jets are possible and why the same theoretical models can be used for both observed astrophysical jets and laboratory simulations.
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95.30.Qd Magnetohydrodynamics and plasmas
95.30.Lz Hydrodynamics
52.72.+v Laboratory studies of space- and astrophysical-plasma processes
52.30.-q Plasma dynamics and flow

The National Ignition Facility: Ushering in a new age for high energy density science

E. I. Moses, R. N. Boyd, B. A. Remington, C. J. Keane, and R. Al-Ayat

Phys. Plasmas 16, 041006 (2009); http://dx.doi.org/10.1063/1.3116505 (13 pages) | Cited 33 times

Online Publication Date: 22 April 2009

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The National Ignition Facility (NIF) [ https://lasers.llnl.gov/ ], completed in March 2009, is the highest energy laser ever constructed. The high temperatures and densities achievable at NIF will enable a number of experiments in inertial confinement fusion and stockpile stewardship, as well as access to new regimes in a variety of experiments relevant to x-ray astronomy, laser-plasma interactions, hydrodynamic instabilities, nuclear astrophysics, and planetary science. The experiments will impact research on black holes and other accreting objects, the understanding of stellar evolution and explosions, nuclear reactions in dense plasmas relevant to stellar nucleosynthesis, properties of warm dense matter in planetary interiors, molecular cloud dynamics and star formation, and fusion energy generation.
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52.57.-z Laser inertial confinement
52.58.Hm Heavy-ion inertial confinement
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back to top Basic Plasma Phenomena, Waves, Instabilities

The Weibel instability inside the electron-positron Harris sheet

Yi-Hsin Liu, M. Swisdak, and J. F. Drake

Phys. Plasmas 16, 042101 (2009); http://dx.doi.org/10.1063/1.3097474 (10 pages) | Cited 2 times

Online Publication Date: 2 April 2009

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Recent full-particle simulations of electron-positron reconnection revealed that the Weibel instability plays an active role in controlling the dynamics of the current layer and maintaining fast reconnection. A four-beam model is developed to explore the development of the instability within a narrow current layer characteristic of reconnection. The problem is reduced to two coupled second-order differential equations, whose growing eigenmodes are obtained via both asymptotic approximations and finite difference methods. Full particle simulations confirm the linear theory and help probe the nonlinear development of the instability. The current layer broadening in the reconnection outflow jet is linked to the scattering of high-velocity streaming particles in the Weibel-generated, out-of-plane magnetic field.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.65.Rr Particle-in-cell method
52.35.Vd Magnetic reconnection
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.)
52.27.Ep Electron-positron plasmas

Effects of line tying on resistive tearing instability in slab geometry

Yi-Min Huang and Ellen G. Zweibel

Phys. Plasmas 16, 042102 (2009); http://dx.doi.org/10.1063/1.3103789 (10 pages) | Cited 9 times

Online Publication Date: 7 April 2009

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The effects of line tying on resistive tearing instability in slab geometry are studied within the framework of reduced magnetohydrodynamics [ B. B. Kadomtsev and O. P. Pogutse, Sov. Phys. JETP 38, 283 (1974) ; H. R. Strauss, Phys. Fluids 19, 134 (1976) ]. It is found that line tying has a stabilizing effect. The tearing mode is stabilized when the system length L is shorter than a critical length Lc, which is independent of the resistivity η. When L is not too much longer than Lc, the growth rate γ is proportional to η. When L is sufficiently long, the tearing mode scaling γ ∼ η3/5 is recovered. The transition from γ ∼ η to γ ∼ η3/5 occurs at a transition length Lt ∼ η−2/5.
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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)
52.55.Tn Ideal and resistive MHD modes; kinetic modes

Fast magnetic reconnection in a kinked current sheet

Keizo Fujimoto

Phys. Plasmas 16, 042103 (2009); http://dx.doi.org/10.1063/1.3106685 (11 pages) | Cited 6 times

Online Publication Date: 9 April 2009

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Magnetic reconnection processes in a kinked current sheet are investigated using three-dimensional electromagnetic particle-in-cell simulations in a large system where both the tearing and kink modes are able to be captured. The spatial resolution is efficiently enhanced using the adaptive mesh refinement and particle splitting-coalescence method. The kink mode scaled by the current sheet width such as kyL ∼ 1 is driven by the ions that are accelerated due to the reconnection electric field in the ion-scale diffusion region. Although the kink mode deforms the current sheet structure drastically, the gross rate of reconnection is almost identical to the case without the kink mode and fast magnetic reconnection is achieved. The magnetic dissipation mechanism is, however, found very different between the cases with and without the kink mode. The kink mode broadens the current sheet width and reduces the electron flow velocity, so that the electron inertia resistivity is decreased. Nevertheless, anomalous dissipation through the electron thermalization compensates the decrease in the inertia resistivity so as to keep a high reconnection rate. This suggests that the electron dynamics in the electron diffusion region is automatically adjusted so as to generate sufficient dissipation for fast magnetic reconnection. The electron thermalization occurs effectively because the electron meandering scale along the current sheet is comparable to the wavelength of the kink mode. On the other hand, two-dimensional simulations in the plane orthogonal to the magnetic field shows that in higher mass ratio cases with mi/me>100 the electron thermalization is caused due to a hybrid-scale mode with wavelength intermediate between the ion and electron inertia lengths kymath ∼ 1 rather than the large-scale kink mode with kyL ∼ 1, because the electron meandering scale is shortened as the mass ratio increases.
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52.35.Vd Magnetic reconnection
52.65.Rr Particle-in-cell method
94.30.cp Magnetic reconnection

Fluctuations in electron-positron plasmas: Linear theory and implications for turbulence

S. Peter Gary and Homa Karimabadi

Phys. Plasmas 16, 042104 (2009); http://dx.doi.org/10.1063/1.3106686 (7 pages) | Cited 1 time

Online Publication Date: 10 April 2009

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Linear kinetic theory of electromagnetic fluctuations in a homogeneous, magnetized, collisionless electron-positron plasma predicts two lightly damped modes propagate at relatively long wavelengths: an Alfvén-like mode with dispersion ωr = k∥mathA and a magnetosonic-like mode with dispersion ωr ≃ kmathA if βe⪡1. Here mathA is the Alfvén speed in an electron-positron plasma and ∥ refers to the direction relative to the background magnetic field Bo. Both modes have phase speeds ωr/k which monotonically decrease with increasing wavenumber. The Alfvén-like fluctuations are almost incompressible, but the magnetosonic-like fluctuations become strongly compressible at short wavelengths and propagation sufficiently oblique to Bo. Using the linear dispersion properties of these modes, scaling relations are derived which predict that turbulence of both modes should be relatively anisotropic, with fluctuating magnetic energy preferentially cascading in directions perpendicular to Bo. Turbulent spectra in the solar wind show two distinct power-law regimes separated by a distinct breakpoint in observed frequency; this characteristic should not be present in electron-positron turbulence because of the absence of whistler-like dispersion. Linear theory properties of the cyclotron and mirror instabilities driven by either electron or positron temperature anisotropies are generally analogous to those of the corresponding instabilities in electron-proton plasmas.
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52.25.Gj Fluctuation and chaos phenomena
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.)
52.35.Ra Plasma turbulence
52.25.Dg Plasma kinetic equations
96.20.Br Origin and evolution

Persistent subplasma-frequency kinetic electrostatic electron nonlinear waves

T. W. Johnston, Y. Tyshetskiy, A. Ghizzo, and P. Bertrand

Phys. Plasmas 16, 042105 (2009); http://dx.doi.org/10.1063/1.3094061 (15 pages) | Cited 6 times

Online Publication Date: 10 April 2009

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Driving a one-dimensional collisionless Maxwellian (Vlasov) plasma with a sufficiently strong longitudinal ponderomotive driver for a sufficiently long time results in a self-sustaining nonsinusoidal wave train with well-trapped electrons even for frequencies well below the plasma frequency, i.e., in the plasma wave spectral gap. Typical phase velocities of these waves are somewhat above the electron thermal velocity. This new nonlinear wave is being termed a kinetic electrostatic electron nonlinear (KEEN) wave. The drive duration must exceed the bounce period τB of the trapped electrons subject to the drive, as calculated from the drive force and the linear plasma response to the drive. For a given wavenumber a wide range of KEEN wave frequencies can be readily excited. The basic KEEN structure is essentially kinetic, with the trapped electron density variation being almost completely shielded by the free electrons, leaving just enough net charge to support the wave.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.25.-b Plasma properties

Tearing modes with pressure gradient effect in pair plasmas

Huishan Cai, Ding Li, and Jian Zheng

Phys. Plasmas 16, 042106 (2009); http://dx.doi.org/10.1063/1.3103787 (6 pages) | Cited 2 times

Online Publication Date: 14 April 2009

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The general dispersion relation of tearing mode with pressure gradient effect in pair plasmas is derived analytically. If the pressure gradients of positron and electron are not identical in pair plasmas, the pressure gradient has significant influence at tearing mode in both collisionless and collisional regimes. In collisionless regime, the effects of pressure gradient depend on its magnitude. For small pressure gradient, the growth rate of tearing mode is enhanced by pressure gradient. For large pressure gradient, the growth rate is reduced by pressure gradient. The tearing mode can even be stabilized if pressure gradient is large enough. In collisional regime, the growth rate of tearing mode is reduced by the pressure gradient. While the positron and electron have equal pressure gradient, tearing mode is not affected by pressure gradient in pair plasmas.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.20.Fs Electron collisions

Lower-hybrid drift instability in a thin current sheet with κ velocity distribution

Feng Huang, Yinhua Chen, Guifen Shi, Zuquan Hu, Haiou Peng, Jugao Zheng, and M. Y. Yu

Phys. Plasmas 16, 042107 (2009); http://dx.doi.org/10.1063/1.3116643 (6 pages) | Cited 2 times

Online Publication Date: 20 April 2009

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The lower-hybrid drift instability (LHDI) in a thin current sheet in the intermediate-wavelength (kymath ∼ 1, where ky, ρe, and ρi are the wave vector and the electron and ion gyroradii, respectively) regime for particles with κ velocity distribution is studied. The latter is more suitable for describing nonthermal distributions with an enhanced high-energy tail and includes the Maxwellian as a limiting case. It is shown that linear electromagnetic LHDI can be excited near the center of the current sheet. The growth rate decreases, but the electromagnetic component of the LHD mode increases with increase in hot particles.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
94.20.wf Plasma waves and instabilities
94.30.Tz Electromagnetic wave propagation

Drift ion acoustic shock waves in an inhomogeneous two-dimensional quantum magnetoplasma

W. Masood, S. Karim, H. A. Shah, and M. Siddiq

Phys. Plasmas 16, 042108 (2009); http://dx.doi.org/10.1063/1.3109663 (8 pages) | Cited 10 times

Online Publication Date: 27 April 2009

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Linear and nonlinear propagation characteristics of drift ion acoustic waves are investigated in an inhomogeneous quantum plasma with neutrals in the background employing the quantum hydrodynamics (QHD) model. In this regard, a quantum Kadomtsev–Petviashvili–Burgers (KPB) equation is derived for the first time. It is shown that the ion acoustic wave couples with the drift wave if the parallel motion of ions is taken into account. Discrepancies in the earlier works on drift solitons and shocks in inhomogeneous plasmas are also pointed out and a correct theoretical framework is presented to study the one-dimensional as well as the two-dimensional propagation of shock waves in an inhomogeneous quantum plasma. Furthermore, the solution of KPB equation is presented using the tangent hyperbolic (tanh) method. The variation of the shock profile with the quantum Bohm potential, collision frequency, and ratio of drift to shock velocity in the comoving frame, v∗/u, are also investigated. It is found that increasing the number density and collision frequency enhances the strength of the shock. It is also shown that the fast drift shock (i.e., v∗/u>0) increases, whereas the slow drift shock (i.e., v∗/u<0) decreases the strength of the shock. The relevance of the present investigation with regard to dense astrophysical environments is also pointed out.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Kt Drift waves
52.35.Sb Solitons; BGK modes

Resonant magnetohydrodynamic waves in high-beta plasmas

M. S. Ruderman

Phys. Plasmas 16, 042109 (2009); http://dx.doi.org/10.1063/1.3119689 (6 pages) | Cited 1 time

Online Publication Date: 28 April 2009

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When a global magnetohydrodynamic (MHD) wave propagates in a weakly dissipative inhomogeneous plasma, the resonant interaction of this wave with either local Alfvén or slow MHD waves is possible. This interaction occurs at the resonant position where the phase velocity of the global wave coincides with the phase velocity of either Alfvén or slow MHD waves. As a result of this interaction a dissipative layer embracing the resonant position is formed, its thickness being proportional to R−1/3, where R⪢1 is the Reynolds number. The wave motion in the resonant layer is characterized by large amplitudes and large gradients. The presence of large gradients causes strong dissipation of the global wave even in very weakly dissipative plasmas. Very often the global wave motion is characterized by the presence of both Alfvén and slow resonances. In plasmas with small or moderate plasma beta β, the resonance positions corresponding to the Alfvén and slow resonances are well separated, so that the wave motion in the Alfvén and slow dissipative layers embracing the Alfvén and slow resonant positions, respectively, can be studied separately. However, when β≳R1/3, the two resonance positions are so close that the two dissipative layers overlap. In this case, instead of two dissipative layers, there is one mixed Alfvén-slow dissipative layer. In this paper the wave motion in such a mixed dissipative layer is studied. It is shown that this motion is a linear superposition of two motions, one corresponding to the Alfvén and the other to the slow dissipative layer. The jump of normal velocity across the mixed dissipative layer related to the energy dissipation rate is equal to the sum of two jumps, one that occurs across the Alfvén dissipative layer and the other across the slow dissipative layer.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.50.Gj Plasma heating by particle beams
96.60.Ly Helioseismology, pulsations, and shock waves
back to top Nonlinear Phenomena, Turbulence, Transport

Effect of resonant helical magnetic fields on plasma rotation

Q. Yu, S. Günter, and K. H. Finken

Phys. Plasmas 16, 042301 (2009); http://dx.doi.org/10.1063/1.3100236 (5 pages) | Cited 15 times

Online Publication Date: 1 April 2009

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The effect of a resonant helical magnetic field on plasma rotation is investigated numerically based on the two fluid equations. It is found that depending on the frequency and the direction of the original plasma rotation, a static helical field of a small amplitude can either increase or decrease the rotation speed. With increasing the field amplitude, the plasma rotation frequency approaches the electron diamagnetic drift frequency but rotates in the ion drift direction. These results provide a new understanding of the recent experimental observations of TEXTOR [ K. H. Finken et al., Phys. Rev. Lett. 94, 015003 (2005) ].
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.25.Dg Plasma kinetic equations
52.65.Kj Magnetohydrodynamic and fluid equation
52.55.Fa Tokamaks, spherical tokamaks

The truncation model of the derivative nonlinear Schrödinger equation

G. Sánchez-Arriaga, T. Hada, and Y. Nariyuki

Phys. Plasmas 16, 042302 (2009); http://dx.doi.org/10.1063/1.3093383 (8 pages) | Cited 7 times

Online Publication Date: 3 April 2009

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The derivative nonlinear Schrödinger (DNLS) equation is explored using a truncation model with three resonant traveling waves. In the conservative case, the system derives from a time-independent Hamiltonian function with only one degree of freedom and the solutions can be written using elliptic functions. In spite of its low dimensional order, the truncation model preserves some features from the DNLS equation. In particular, the modulational instability criterion fits with the existence of two hyperbolic fixed points joined by a heteroclinic orbit that forces the exchange of energy between the three waves. On the other hand, numerical integrations of the DNLS equation show that the truncation model fails when wave energy is increased or left-hand polarized modulational unstable modes are present. When dissipative and growth terms are added the system exhibits a very complex dynamics including appearance of several attractors, period doubling bifurcations leading to chaos as well as other nonlinear phenomenon. In this case, the validity of the truncation model depends on the strength of the dissipation and the kind of attractor investigated.
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52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
05.45.-a Nonlinear dynamics and chaos

Truncation model in the triple-degenerate derivative nonlinear Schrödinger equation

G. Sánchez-Arriaga, T. Hada, and Y. Nariyuki

Phys. Plasmas 16, 042303 (2009); http://dx.doi.org/10.1063/1.3093394 (9 pages) | Cited 2 times

Online Publication Date: 3 April 2009

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The triple-degenerate derivative nonlinear Schrödinger (TDNLS) system modified with resistive wave damping and growth is truncated to study the coherent coupling of four waves, three Alfven and one acoustic, near resonance. In the conservative case, the truncation equations derive from a time independent Hamiltonian function with two degrees of freedom. Using a Poincare map analysis, two parameters regimes are explored. In the first regime we check how the modulational instability of the TDNLS system affects to the dynamics of the truncation model, while in the second one the exact triple degenerated case is discussed. In the dissipative case, the truncation model gives rise to a six dimensional flow with five free parameters. Computing some bifurcation diagrams the dependence with the sound to Alfven velocity ratio as well as the Alfven modes involved in the truncation is analyzed. The system exhibits a wealth of dynamics including chaotic attractor, several kinds of bifurcations, and crises. The truncation model was compared to numerical integrations of the TDNLS system.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
03.65.Ge Solutions of wave equations: bound states
02.30.Uu Integral transforms

Global characteristics of zonal flows due to the effect of finite bandwidth in drift wave turbulence

K. Uzawa, Jiquan Li, and Y. Kishimoto

Phys. Plasmas 16, 042304 (2009); http://dx.doi.org/10.1063/1.3097490 (7 pages) | Cited 1 time

Online Publication Date: 6 April 2009

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The spectral effect of the zonal flow (ZF) on its generation is investigated based on the Charney–Hasegawa–Mima turbulence model. It is found that the effect of finite ZF bandwidth qualitatively changes the characteristics of ZF instability. A spatially localized (namely, global) nonlinear ZF state with an enhanced, unique growth rate for all spectral components is created under a given turbulent fluctuation. It is identified that such state originates from the successive cross couplings among Fourier components of the ZF and turbulence spectra through the sideband modulation. Furthermore, it is observed that the growth rate of the global ZF is determined not only by the spectral distribution and amplitudes of turbulent pumps as usual, but also statistically by the turbulence structure, namely, their probabilistic initial phase factors. A ten-wave coupling model of the ZF modulation instability involving the essential effect of the ZF spectrum is developed to clarify the basic features of the global nonlinear ZF state.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Kt Drift waves
52.35.Ra Plasma turbulence

Nonlinear resonant absorption of fast magnetoacoustic waves in strongly anisotropic and dispersive plasmas

Christopher T. M. Clack and Istvan Ballai

Phys. Plasmas 16, 042305 (2009); http://dx.doi.org/10.1063/1.3104714 (11 pages) | Cited 1 time

Online Publication Date: 7 April 2009

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The nonlinear theory of driven magnetohydrodynamics (MHD) waves in strongly anisotropic and dispersive plasmas, developed for slow resonance by Clack and Ballai [Phys. Plasmas 15, 2310 (2008)] and Alfvén resonance by Clack et al. [Astron. Astrophys. 494, 317 (2009)] , is used to study the weakly nonlinear interaction of fast magnetoacoustic (FMA) waves in a one-dimensional planar plasma. The magnetic configuration consists of an inhomogeneous magnetic slab sandwiched between two regions of semi-infinite homogeneous magnetic plasmas. Laterally driven FMA waves penetrate the inhomogeneous slab interacting with the localized slow or Alfvén dissipative layer and are partly reflected, dissipated, and transmitted by this region. The nonlinearity parameter defined by Clack and Ballai (2008) is assumed to be small and a regular perturbation method is used to obtain analytical solutions in the slow dissipative layer. The effect of dispersion in the slow dissipative layer is to further decrease the coefficient of energy absorption, compared to its standard weakly nonlinear counterpart, and the generation of higher harmonics in the outgoing wave in addition to the fundamental one. The absorption of external drivers at the Alfvén resonance is described within the linear MHD with great accuracy.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
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.)

Dynamics of nonlinearly interacting magnetic electron drift vortex modes in a nonuniform plasma

B. Eliasson, P. K. Shukla, and V. P. Pavlenko

Phys. Plasmas 16, 042306 (2009); http://dx.doi.org/10.1063/1.3103785 (8 pages) | Cited 1 time

Online Publication Date: 10 April 2009

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A simulation study of dynamical evolution of nonlinearly interacting two-dimensional magnetic electron drift vortex (MEDV) modes in a nonuniform plasma is presented. Depending on the equilibrium density and temperature gradients, the system can either be stable or unstable. The unstable system reveals spontaneous generation of magnetic fields from noise level, and large-scale magnetic field structures are formed. When the system is linearly stable, one encounters MEDV mode turbulence in which there is a competition between zonons (zonal flows) and streamers. For large MEDV mode amplitudes, one encounters the formation of localized and small-scale magnetic vortices and vortex pairs with scale sizes of the order of the electron skin depth. The MEDV turbulence exhibits nonuniversal (non-Kolmogorov-type) spectra for different sets of plasma parameters. The relevance of this work to laboratory and cosmic plasmas is briefly mentioned.
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52.25.Gj Fluctuation and chaos phenomena
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
98.62.En Electric and magnetic fields

Forward and inverse cascades in decaying two-dimensional electron magnetohydrodynamic turbulence

C. J. Wareing and R. Hollerbach

Phys. Plasmas 16, 042307 (2009); http://dx.doi.org/10.1063/1.3111033 (8 pages) | Cited 6 times

Online Publication Date: 15 April 2009

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Electron magnetohydrodynamic (EMHD) turbulence in two dimensions is studied via high-resolution numerical simulations with a normal diffusivity. The resulting energy spectra asymptotically approach a k−5/2 law with increasing RB, the ratio of the nonlinear to linear time scales in the governing equation. No evidence is found of a dissipative cutoff, consistent with nonlocal spectral energy transfer. Dissipative cutoffs found in previous studies are explained as artificial effects of hyperdiffusivity. Relatively stationary structures are found to develop in time, rather than the variability found in ordinary or MHD turbulence. Further, EMHD turbulence displays scale-dependent anisotropy with reduced energy transfer in the direction parallel to the uniform background field, consistent with previous studies. Finally, the governing equation is found to yield an inverse cascade, at least partially transferring magnetic energy from small to large scales.
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52.35.Ra Plasma turbulence
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
95.30.Qd Magnetohydrodynamics and plasmas
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