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Aug 2003

Volume 10, Issue 8, pp. 3043-3440

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Nonstationary nonlinear dust-acoustic waves in unmagnetized plasma

Nikhil Chakrabarti and M. S. Janaki

Phys. Plasmas 10, 3043 (2003); http://dx.doi.org/10.1063/1.1588309 (4 pages) | Cited 2 times

Online Publication Date: 18 July 2003

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The nonstationary and nonlinear dust-acoustic wave is considered in the framework of the Lagrangian fluid description. A single nonlinear equation and its solutions are obtained for dust-acoustic waves with nontrivial space and time dependence in both the large and small amplitude limit. In the absence of linear dispersion solutions in the large amplitude limit, it is demonstrated that under well-defined initial and boundary conditions the amplitude of the solutions is decreasing and the spatial profile spreads. This is a new class of nonlinear solutions leading to short-lived nonlinear structures. In the small amplitude limit, the soliton-like solution indicates close association with Korteweg–de Vries solitons. © 2003 American Institute of Physics.
Show PACS
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.27.Lw Dusty or complex plasmas; plasma crystals
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Sb Solitons; BGK modes
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back to top Basic Plasma Phenomena, Waves, Instabilities

Modification of the shielding and wake potentials in a streaming dusty magnetoplasma

M. Salimullah, P. K. Shukla, M. Nambu, H. Nitta, O. Ishihara, and A. M. Rizwan

Phys. Plasmas 10, 3047 (2003); http://dx.doi.org/10.1063/1.1589008 (4 pages) | Cited 3 times

Online Publication Date: 18 July 2003

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The effect of an external magnetic field on the Debye shielding and dynamical wake potentials has been examined analytically in a uniform dusty plasma containing equilibrium ion and dust flows. The effects of the ion polarization drift and dust particle dynamics on the strength and the effective length of the new static Debye shielding potential and the dynamical oscillatory potential are studied. It is found that for the supersonic ion flow, the modified Debye–Hückel screening length, and the effective length, L∥, of the oscillatory wake potential due to the modified dust acoustic modes [cf. Eqs. (7) and (17)] become larger by a factor of ωpi/ωci than those due to the usual dust-acoustic wave, where ωpi and ωci are the ion plasma and ion gyrofrequencies, respectively. © 2003 American Institute of Physics.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.25.Vy Impurities in plasmas

Quantum screening effects on the electron-ion occurrence scattering time advance in strongly coupled semiclassical plasmas

Mi-Young Song and Young-Dae Jung

Phys. Plasmas 10, 3051 (2003); http://dx.doi.org/10.1063/1.1589750 (5 pages)

Online Publication Date: 18 July 2003

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Quantum screening effects on the occurrence scattering time advance for elastic electron-ion collisions in strongly coupled semiclassical plasmas are investigated using the second-order eikonal analysis. The electron-ion interaction in strongly coupled semiclassical plasmas is obtained by the pseudopotential model taking into account the plasma screening and quantum effects. It is found that the quantum-mechanical effects significantly reduce the occurrence scattering time advance. It is also found that the occurrence scattering time advance increases with increasing Debye length. It is quite interesting to note that the domain of the maximum occurrence time advance is localized for the forward scattering case. The region of the scaled thermal de Broglie wave length (math) for the maximum occurrence time advance is found to be 0.4 ⩽ math ⩽ 1.4. © 2003 American Institute of Physics.
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52.20.-j Elementary processes in plasmas
52.20.Fs Electron collisions
34.80.Bm Elastic scattering

Complete nondestructive diagnostic of nonneutral plasmas based on the detection of electrostatic modes

M. Amoretti, G. Bonomi, A. Bouchta, P. D. Bowe, C. Carraro, C. L. Cesar, M. Charlton, M. Doser, A. Fontana, M. C. Fujiwara, R. Funakoshi, P. Genova, J. S. Hangst, R. S. Hayano, L. V. Jørgensen, et al.

Phys. Plasmas 10, 3056 (2003); http://dx.doi.org/10.1063/1.1591187 (9 pages) | Cited 19 times

Online Publication Date: 18 July 2003

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The detection of electrostatic nonneutral plasma modes in the ATHENA (ApparaTus for High precision Experiment on Neutral Antimatter) experiment [M. Amoretti, C. Amsler, G. Bonomi et al., Nature (London) 419, 456 (2002)] is described. A complete nondestructive diagnostic of the plasma based on a fit to the line shape of the function describing the power transmitted through the plasma around the frequency of the fundamental mode is developed and the experimental results are presented and discussed. © 2003 American Institute of Physics.
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52.27.Jt Nonneutral plasmas
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.70.-m Plasma diagnostic techniques and instrumentation
36.10.-k Exotic atoms and molecules (containing mesons, antiprotons and other unusual particles)
back to top Nonlinear Phenomena, Turbulence, Transport

Anisotropic weak whistler wave turbulence in electron magnetohydrodynamics

S. Galtier and A. Bhattacharjee

Phys. Plasmas 10, 3065 (2003); http://dx.doi.org/10.1063/1.1584433 (12 pages) | Cited 22 times

Online Publication Date: 18 July 2003

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A weak wave turbulence theory is given for electron magnetohydrodynamics in the presence of a strong and uniform external magnetic field. Using helicity decomposition, the wave kinetic equations for energy and magnetic helicity are derived at the level of three-wave interactions between whistler waves. It is shown that nonlinear interactions of whistler waves transfer energy and magnetic helicity mainly in the direction perpendicular to the external magnetic field. The anisotropic turbulence thus generated has exact stationary power law solutions which scale as k⊥−5/2k∥−1/2 for the energy spectrum and k⊥−7/2k∥−1/2 for the magnetic helicity spectrum. © 2003 American Institute of Physics.
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52.30.Ex Two-fluid and multi-fluid plasmas
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.)
52.35.Ra Plasma turbulence

Spectral properties of decaying turbulence in electron magnetohydrodynamics

T. M. Abdalla, V. P. Lakhin, T. J. Schep, and E. Westerhof

Phys. Plasmas 10, 3077 (2003); http://dx.doi.org/10.1063/1.1588308 (16 pages) | Cited 2 times

Online Publication Date: 18 July 2003

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The spectral properties of decaying turbulence in 2½-dimensional electron magnetohydrodynamics are studied numerically. In the range kde<1 the energy exhibits a direct cascade while mean square momentum exhibits an inverse cascade. Their spectra are characterized by k−7/3 and k−13/3, respectively. The self-similar decay state of the turbulence is reached after an initial phase of fast exchange between the axial and poloidal magnetic energies. The time behavior t−2/3 of the total energy is found to be consistent with that obtained from selective decay. The maximum of the energy spectrum shifts towards low mode numbers and decays in time as t−1, in agreement with the infrared scaling of the turbulence. In the large de limit, both energy and mean square generalized momentum exhibit direct cascades. No stationary turbulent state could be found as long as the axial kinetic energy is large as compared to the poloidal kinetic energy initially. The global physical quantities decay well before turbulent macroscopic quantities have established similar space–time behavior, and the turbulence is infected by the lack of stationarity. The system decouples into a Navier–Stokes equation and a passive scalar equation only if the poloidal kinetic energy is larger than or equal to the axial kinetic energy. In this limit the k−5/3 and k−3 spectra of the poloidal kinetic energy are recovered. © 2003 American Institute of Physics.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Ra Plasma turbulence
52.25.Dg Plasma kinetic equations

Interaction of a wave packet with a thin electron beam spiraling in a magnetized plasma

C. Krafft and A. S. Volokitin

Phys. Plasmas 10, 3093 (2003); http://dx.doi.org/10.1063/1.1591183 (10 pages) | Cited 4 times

Online Publication Date: 18 July 2003

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The nonlinear processes governing the resonant interaction of a packet of lower hybrid waves with a radially bounded electron beam spiraling in a magnetized plasma are investigated. In particular, the paper tries to answer the fundamental following questions: What are the causes of the beam bunching and the main agents of the beam self-organization occurring during the nonlinear wave–particle evolution? What is the influence of the wave packet on the stability of the formed bunches? This paper shows that, owing to the presence of wave energy dissipation out of the bounded beam volume, a competition takes place between the beam relaxation and the particle bunching processes, leading to the structuring of the beam over long distances from the injection point. In particular, two main mechanisms govern the behavior of the particles in resonance with the waves: First, the process of particle bunching which gives rise to dynamically stable and long living bunches of particles which keep resonance and strong correlations with several waves of the packet while continuously decelerated (Cherenkov resonance is considered) in the frame moving with the initial parallel beam velocity and, second, a process of particle diffusion in the velocity space concerning particles which do not experience trapping by waves or which leave a bunch through the action of large stochastic oscillations. This diffusion process cannot be well described in the frame of the weak turbulence theory, as it is noticeably perturbed by the presence of a large number of small unstable bunches which appear, merge together and disappear during the system’s evolution. © 2003 American Institute of Physics.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.40.Mj Particle beam interactions in plasmas
52.25.Fi Transport properties
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.35.Vd Magnetic reconnection
52.55.Tn Ideal and resistive MHD modes; kinetic modes
52.35.Ra Plasma turbulence
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

Electromagnetic properties of the lower-hybrid drift instability in a thin current sheet

William Daughton

Phys. Plasmas 10, 3103 (2003); http://dx.doi.org/10.1063/1.1594724 (17 pages) | Cited 68 times

Online Publication Date: 18 July 2003

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The linear and nonlinear properties of the lower-hybrid drift instability are examined in a thin current sheet with thickness comparable to a thermal ion gyroradius ρi ∼ L. The linear Vlasov stability is calculated using a formally exact technique in which the orbit integrals are treated numerically and the eigenvalue problem for the resulting system of integrodifferential equations is solved using a finite element representation of the eigenfunction. For the fastest growing lower-hybrid modes with wavelength on the electron gyroscale (kyρe ∼ 1), the resulting mode structure is localized on the edge of the current sheet. However, for modes with wavelengths intermediate between the electron and ion gyroscale kymath ∼ 1, the lower-hybrid instability has a significant electromagnetic component to the mode structure which is localized in the central region of the sheet. The addition of a weak guide field complicates the mode structure and gives rise to fluctuations in all three components of the magnetic field. These new predictions from linear Vlasov theory are confirmed using fully kinetic particle-in-cell simulations which indicate the modes saturate at large amplitude in the central region of the sheet. These results suggest the possibility that the electromagnetic fluctuations may potentially influence the development of magnetic reconnection. © 2003 American Institute of Physics.
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52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.35.Vd Magnetic reconnection
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.65.Rr Particle-in-cell method
52.25.Gj Fluctuation and chaos phenomena

Hall current effects in dynamic magnetic reconnection solutions

I. J. D. Craig, J. Heerikhuisen, and P. G. Watson

Phys. Plasmas 10, 3120 (2003); http://dx.doi.org/10.1063/1.1590980 (11 pages) | Cited 13 times

Online Publication Date: 18 July 2003

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The impact of Hall current contributions on flow driven planar magnetic merging solutions is discussed. The Hall current is important if the dimensionless Hall parameter (or normalized ion skin depth) satisfies cH>η, where η is the inverse Lundquist number for the plasma. A dynamic analysis of the problem shows, however, that the Hall current initially manifests itself, not by modifying the planar reconnection field, but by inducing a non-reconnecting perpendicular “separator” component in the magnetic field. Only if the stronger condition cH2>η is satisfied can Hall currents be expected to affect the planar merging. These analytic predictions are then tested by performing a series of numerical experiments in periodic geometry, using the full system of planar magnetohydrodynamic (MHD) equations. The numerical results confirm that the nature of the merging changes dramatically when the Hall coupling satisfies cH2>η. In line with the analytic treatment of sheared reconnection, the coupling provided by the Hall term leads to the emergence of multiple current layers that can enhance the global Ohmic dissipation at the expense of the reconnection rate. However, the details of the dissipation depend critically on the symmetries of the simulation, and when the merging is “head-on” (i.e., comprises fourfold symmetry) the reconnection rate can be enhanced. © 2003 American Institute of Physics.
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52.35.Vd Magnetic reconnection
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.25.Fi Transport properties
52.65.Kj Magnetohydrodynamic and fluid equation

Magnetohydrodynamic modeling of two-dimensional reconnection in the Magnetic Reconnection Experiment

V. S. Lukin and S. C. Jardin

Phys. Plasmas 10, 3131 (2003); http://dx.doi.org/10.1063/1.1591182 (8 pages) | Cited 3 times

Online Publication Date: 18 July 2003

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A two-dimensional magnetohydrodynamics (MHD) code is used to investigate the dynamical evolution of driven reconnection in the Magnetic Reconnection Experiment (MRX) [M. Yamada et al., Phys. Plasmas 7, 1781 (2000)]. The initial conditions and dimensionless parameters of the simulation are set to be similar to the experimental values. Many features of the time-evolution of magnetic configurations for both co- and counter-helicity reconnection in MRX are successfully reproduced in the framework of resistive MHD. The resistive MHD model is then augmented by the addition of a “model Hall” term to begin to assess the importance of two-fluid physics in the experiment. The effective decoupling of the ion fluid from the reconnecting magnetic field due to the model Hall term is shown to be important during the early dynamic X-phase of MRX reconnection, while effectively negligible during the late “steady-state” Y-phase, when plasma heating takes place. These results are consistent with the available experimental evidence. Based on simple symmetry considerations, an experiment to directly measure the Hall effect in MRX configuration is proposed and numerical evidence for the expected outcome is given. © 2003 American Institute of Physics.
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52.35.Vd Magnetic reconnection
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.50.-b Plasma production and heating
52.65.Kj Magnetohydrodynamic and fluid equation
52.25.Fi Transport properties

Hall magnetohydrodynamics of neutral layers

J. D. Huba and L. I. Rudakov

Phys. Plasmas 10, 3139 (2003); http://dx.doi.org/10.1063/1.1582474 (12 pages) | Cited 8 times

Online Publication Date: 18 July 2003

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New analytical and numerical results of the dynamics of inhomogeneous, reversed field current layers in the Hall limit (i.e., characteristic length scales ≲ the ion inertial length) are presented. Specifically, the two- and three-dimensional evolution of a current layer that supports a reversed field plasma configuration and has a density gradient along the current direction is studied. The two-dimensional study demonstrates that a density inhomogeneity along the current direction can dramatically redistribute the magnetic field and plasma via magnetic shock-like or rarefaction waves. The relative direction between the density gradient and current flow plays a critical role in the evolution of the current sheet. One important result is that the current sheet can become very thin rapidly when the density gradient is directed opposite to the current. The three-dimensional study uses the same plasma and field configuration as the two-dimensional study but is also initialized with a magnetic field perturbation localized along the current channel upstream of the plasma inhomogeneity. The perturbation induces a magnetic wave structure that propagates in the direction of the electron drift (i.e., opposite to the current). The propagating wave structure is a Hall phenomenon associated with magnetic field curvature. The interaction between the propagating wave structure and the evolving current layer can lead to rapid magnetic field line reconnection. The results are applied to laboratory and space plasma processes. © 2003 American Institute of Physics.  
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Tc Shock waves and discontinuities

Double tearing mode in plasmas with anomalous electron viscosity

J. Q. Dong, S. M. Mahajan, and W. Horton

Phys. Plasmas 10, 3151 (2003); http://dx.doi.org/10.1063/1.1581286 (9 pages) | Cited 22 times

Online Publication Date: 18 July 2003

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The linear behavior of the double tearing mode in plasmas with a phenomenological anomalous electron viscosity is investigated within the framework of magnetohydrodynamic theory. In the large Reynolds number R = τv/τh (τv and τh are, respectively, the viscosity penetration time of the magnetic field and the Alfvén time for a plasma sheet of width a) limit, the growth rate is found to scale as R−1/5 if the two resonant surfaces, at x = ±xs, are close enough to satisfy xs/a≪(kya)−11/15R−1/15. For larger separation between the resonant surfaces, the growth rate transits to a R−1/3 scaling. The transition occurs at xs/a ∼ (kya)−11/15R−1/15. The R−1/5 is shown to be closely correlated with the violation of the constant-ψ approximation. The nonlinear velocity perturbations associated with the unstable double tearing mode are estimated to saturate at a level high enough to serve as a trigger for the formation of transport barriers observed in advanced tokamaks. © 2003 American Institute of Physics.
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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.Fa Tokamaks, spherical tokamaks

Parametric instabilities of Alfvén waves in a dusty plasma

M. P. Hertzberg, N. F. Cramer, and S. V. Vladimirov

Phys. Plasmas 10, 3160 (2003); http://dx.doi.org/10.1063/1.1591184 (8 pages) | Cited 17 times

Online Publication Date: 18 July 2003

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The excitation of low frequency modes of oscillations in a magnetized dusty plasma with parametric pumping of the magnetic field is analyzed. The dust is taken to be stationary, but acts as a sink for negative charge: The absence of a proportion of the electrons in the overall neutral plasma modifies the dispersion properties of the pump and excited waves. The pump is a magnetoacoustic wave modified by the dust, and the excited waves are modifications of Alfvén waves due to the dust and due to ion cyclotron effects. The equation of motion governing the perturbed plasma is derived and pump wave fields are found. The stability of the pump to modes propagating parallel to the magnetic field is investigated as a function of the plasma parameters. It is found that pairs of slow and fast parallel propagating modes are parametrically excited. The growth rates of the various interactions are calculated, and it is shown that the growth rates of slow–fast and fast–fast mode interactions can be maximized by varying the proportion of negative charge on the dust. © 2003 American Institute of Physics.
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52.27.Lw Dusty or complex plasmas; plasma crystals
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.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.65.Vv Perturbative methods

Linear and nonlinear properties of dust-acoustic waves in collisional, magnetized dusty plasmas

Waleed M. Moslem

Phys. Plasmas 10, 3168 (2003); http://dx.doi.org/10.1063/1.1591768 (6 pages) | Cited 5 times

Online Publication Date: 18 July 2003

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Effects of dust-neutral collision and densities of positive ions and electrons have been investigated for the propagation of dust-acoustic waves (DAWs) in magnetized dusty plasmas. It is found that, due to collisions, the DAWs damp waves and the damping rate of the waves depends mainly on the collision frequency (i.e., if there are no collisions the waves do not damp waves). The collisions are found to significantly change the basic properties (viz., the amplitude and the width) of the DAWs. The densities of positive ions and electrons have important roles in the behavior of the DAWs. The present analysis shows that only rarefactive solitary waves exist in the system. This investigation can be relevant to the DAWs in various space plasma environments, such as Jupiter’s ring, the F ring of Saturn, and interstellar dusty clouds. © 2003 American Institute of Physics.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.27.Lw Dusty or complex plasmas; plasma crystals
52.25.Kn Thermodynamics of plasmas

Experimental investigation of isotope scaling of anomalous ion thermal transport

V. Sokolov and A. K. Sen

Phys. Plasmas 10, 3174 (2003); http://dx.doi.org/10.1063/1.1592801 (7 pages) | Cited 2 times

Online Publication Date: 18 July 2003

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There is a significant divergence between tokamak experimental results and most theoretical predictions in isotopic mass scaling of transport. It indicates a fundamental open physics issue of great importance, as well as a serious question for magnetic fusion. This divergence has motivated a series of basic physics experiments in the Columbia Linear Machine (CLM) [R. Scarmozzino et al., Phys. Rev. Lett. 57, 1729 (1986)], which are reported here. The experimental focus is on the anomalous ion thermal conduction due to ion temperature gradient driven modes in two different gases: hydrogen and deuterium. Unlike in tokamaks, all plasma parameters are kept nearly identical in the CLM for both gases. The results indicate inverse dependence of ion thermal conductivity on the isotopic mass close to K⊥ ∼ Ai−0.5 to −0.8, where Ai is the mass number of the isotope of hydrogen. This is close to the tokamak results, but in contradiction to most theoretical models, especially of the Bohm/gyro-Bohm-types. © 2003 American Institute of Physics.
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52.25.Fi Transport properties
52.25.Kn Thermodynamics of plasmas
52.55.-s Magnetic confinement and equilibrium
52.55.Fa Tokamaks, spherical tokamaks
52.55.Jd Magnetic mirrors, gas dynamic traps

Filamentary magnetohydrodynamic simulation model, current-vortex method

Yuichi Yatsuyanagi, Toshikazu Ebisuzaki, Tadatsugu Hatori, and Tomokazu Kato

Phys. Plasmas 10, 3181 (2003); http://dx.doi.org/10.1063/1.1594725 (7 pages) | Cited 4 times

Online Publication Date: 18 July 2003

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A two-dimensional simulation model of the “magnetohydrodynamic (MHD)” vortex method, current-vortex method, is developed. The concept is based on the previously developed current-vortex filament model in three-dimensional space. It is assumed that electric current and vorticity have discontinuous filamentary (point) distributions on the two-dimensional plane, and both the point electric current and the point vortex are confined in a filament. In other words, they share the same point on the two-dimensional plane, which is called the “current-vortex filament.” The spatial profiles of the electric current and the vorticity are determined by the sum of such filaments. Time development equations for a filament are obtained by integrating the two-dimensional MHD equations around the filament. It is found that a special-purpose computer, MDGRAPE-2, is capable not only of molecular dynamics simulations but also of MHD simulations, because MDGRAPE-2 accelerates calculations of the Biot–Savart integral. The current-vortex method on MDGRAPE-2 reproduces the result obtained by the traditional MHD code on a general-purpose computer. © 2003 American Institute of Physics.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
47.32.C- Vortex dynamics
52.65.Kj Magnetohydrodynamic and fluid equation

Simulations of diocotron instability using a special-purpose computer, MDGRAPE-2

Yuichi Yatsuyanagi, Yasuhito Kiwamoto, Toshikazu Ebisuzaki, Tadatsugu Hatori, and Tomokazu Kato

Phys. Plasmas 10, 3188 (2003); http://dx.doi.org/10.1063/1.1592516 (8 pages) | Cited 3 times

Online Publication Date: 18 July 2003

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The diocotron instability in a low-density non-neutral electron plasma is examined via numerical simulations. For the simulations, a current-vortex filament model and a special-purpose computer, MDGRAPE-2 are used. In the previous work, a simulation method based on the current-vortex filament model, which is called “current-vortex method,” is developed. It is assumed that electric current and vorticity have discontinuous filamentary distributions, and both point electric current and point vortex are confined in a filament, which is called “current-vortex filament.” In this paper, the current-vortex method with no electric current is applied to simulations of the non-neutral electron plasma. This is equivalent to the traditional point-vortex method. MDGRAPE-2 was originally designed for molecular dynamics simulations. It accelerates calculations of the Coulomb interactions, the van der Waals interactions and so on. It can also be used to accelerate calculations of the Biot–Savart integral. The diocotron modes reproduced by the simulations agree with the result predicted by linear theory. This indicates that the current-vortex method is applicable to problems of the non-neutral plasma. The linear growth rates of the diocotron instability in the simulations also agree with the theoretical ones. This implies that MDGRAPE-2 gives the sufficiently accurate results for the calculations of the current-vortex method. A mechanism of merging of electron clumps is demonstrated by the simulations. It is concluded that the electric field induced by the conducting wall makes the nonlinear stage unstable and causes the clumps to merge. © 2003 American Institute of Physics.
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52.27.Jt Nonneutral plasmas
47.32.C- Vortex dynamics
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
back to top Magnetically Confined Plasmas, Heating, Confinement

Alfvén waves in gyrokinetic plasmas

W. W. Lee and H. Qin

Phys. Plasmas 10, 3196 (2003); http://dx.doi.org/10.1063/1.1590666 (8 pages) | Cited 9 times

Online Publication Date: 18 July 2003

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A brief comparison of the properties of Alfvén waves that are based on the gyrokinetic description with those derived from the magnetohydrodynamics (MHD) equations is presented. The critical differences between these two approaches are the treatment of the ion polarization effects. As such, the compressional Alfvén waves in a gyrokinetic plasma can be eliminated through frequency ordering, whereas geometric simplifications are needed to decouple the shear Alfvén waves from the compressional Alfvén waves within the context of MHD. Theoretical and numerical procedures of using gyrokinetic particle simulation for studying microturbulence and kinetic-MHD physics including finite Larmor radius effects are also presented. © 2003 American Institute of Physics.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.65.Kj Magnetohydrodynamic and fluid equation
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.65.-y Plasma simulation
52.35.Ra Plasma turbulence
52.25.Dg Plasma kinetic equations

Multigrid particle-in-cell simulations of plasma microturbulence

J. L. V. Lewandowski

Phys. Plasmas 10, 3204 (2003); http://dx.doi.org/10.1063/1.1591186 (8 pages) | Cited 9 times

Online Publication Date: 18 July 2003

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A new scheme to accurately retain kinetic electron effects in particle-in-cell (PIC) simulations for the case of electrostatic drift waves is presented. The splitting scheme, which is based on exact separation between adiabatic and nonadiabatic electron responses, is shown to yield more accurate linear growth rates than the standard δf scheme. The linear and nonlinear elliptic problems that arise in the splitting scheme are solved using a multigrid solver. The multigrid PIC approach offers an attractive path, both from the physics and numerical points of view, to simulate kinetic electron dynamics in global toroidal plasmas. © 2003 American Institute of Physics.
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52.35.Kt Drift waves
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Ra Plasma turbulence

Effect of a ferromagnetic wall on low β tearing modes in the Japan Atomic Energy Research Institute Fusion Torus-2 Modified

M. Bakhtiari, M. Azumi, K. Tsuzuki, K. Kamiya, H. Kawashima, Y. Kusama, M. Sato, and K. Hoshino

Phys. Plasmas 10, 3212 (2003); http://dx.doi.org/10.1063/1.1593022 (5 pages) | Cited 6 times

Online Publication Date: 18 July 2003

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A ferritic steel wall, which might be employed in fusion demonstration reactors, has been installed in Japan Atomic Energy Research Institute Fusion Torus-2 Modified [Nucl. Fusion 41, 257 (2001)] to study the applicability of ferromagnetic walls to plasmas. The tearing mode equation is solved in presence of a ferromagnetic/resistive wall to study the effect of the ferromagnetism on the tearing mode stability in tokamaks. It is shown that a ferromagnetic wall has a weak effect on the surface tearing modes depending on the current profile. The destabilization effect due to the attraction of the perturbed magnetic field by permeability is shown to be very small compared to the stabilization effect of the conducting wall. © 2003 American Institute of Physics.
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52.55.Fa Tokamaks, spherical tokamaks
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.40.Hf Plasma-material interactions; boundary layer effects
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
75.50.Bb Fe and its alloys

Shear Alfvén continua in stellarators

D. A. Spong, R. Sanchez, and A. Weller

Phys. Plasmas 10, 3217 (2003); http://dx.doi.org/10.1063/1.1590316 (8 pages) | Cited 13 times

Online Publication Date: 18 July 2003

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Shear Alfvén continua have been calculated for stellarators over a range of shapes and aspect ratios as a first step toward understanding Alfvén instability induced fast ion losses in such systems and possible means for minimizing these losses. Stellarators introduce strong poloidal/toroidal couplings in both ∣B∣ and the gρρ metric coefficient that can induce new continuum gap structures not present in axisymmetric tokamaks. Low field period (Nfp = 2–3), low aspect ratio devices result in strongly coupled toroidal mode families (n = ±n0,±n0±Nfp,±n0±2Nfp, etc.) that lead to helically coupled Alfvén gaps at lower frequencies and with wider gap structures than are the case for larger aspect ratio, higher field period stellarator devices. © 2003 American Institute of Physics.
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52.55.Jd Magnetic mirrors, gas dynamic traps
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.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

Theory-based modeling of particle transport in ASDEX Upgrade H-mode plasmas, density peaking, anomalous pinch and collisionality

C. Angioni, A. G. Peeters, G. V. Pereverzev, F. Ryter, and G. Tardini

Phys. Plasmas 10, 3225 (2003); http://dx.doi.org/10.1063/1.1589009 (15 pages) | Cited 45 times

Online Publication Date: 18 July 2003

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The theoretical prediction of density profiles in tokamak plasmas plays a major role for the prediction of the plasma performance in a fusion reactor. The density peaking measured in plasmas in high confinement mode of the ASDEX Upgrade tokamak [O. Gruber, H.-S. Bosch, S. Günter et al., Nucl. Fusion 39, 1321 (1999)] is shown to decrease with increasing collisionality. This experimental behavior is explained with a theoretical fluid transport model for ion temperature gradient and trapped electron modes, GLF23, which includes a valid description of the effects of collisions on these instabilities. Collisionless reactive models, like the Weiland model, are in disagreement with the experimental observations. The difference between the predictions of the two models must be ascribed to collisionality. This has been ascertained by a detailed comparison of the physics content of the two models and by the implementation of modified, collisionless versions of the GLF23 model, which yield results analogous to those of the Weiland model and in disagreement with the experiment. It is shown that the anomalous particle pinch decreases with collisionality and the relative role of the neoclassical Ware pinch becomes important at high collisionality, that is close to the density limit in present large tokamak experiments, while it is practically negligible at low collisionality. The present results reconciliate apparently contradictory observations on the existence of an anomalous particle pinch collected so far in tokamaks.© 2003 American Institute of Physics.
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52.25.Fi Transport properties
52.35.Kt Drift waves
52.55.Fa Tokamaks, spherical tokamaks

Self-consistent equilibrium model of low aspect-ratio toroidal plasma with energetic beam ions

E. V. Belova, N. N. Gorelenkov, and C. Z. Cheng

Phys. Plasmas 10, 3240 (2003); http://dx.doi.org/10.1063/1.1592155 (12 pages) | Cited 7 times

Online Publication Date: 18 July 2003

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A theoretical model is developed which allows the self-consistent inclusion of the effects of energetic beam ions in equilibrium calculations of low-aspect-ratio toroidal devices. A two-component plasma is considered, where the energetic ions are treated using a kinetic Vlasov description, while a one-fluid magnetohydrodynamic description is used to represent the thermal plasma. The model allows for an anisotropic distribution function and a large Larmor radius of the beam ions. Numerical results are obtained for neutral-beam-heated plasmas in the National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, Y.-K. M. Peng et al., Nucl. Fusion 40, 557 (2000)]. Self-consistent equilibria with an anisotropic fast ion distribution have been calculated for NSTX. It is shown for typical experimental parameters that the contribution of the energetic neutral beam ions to the total current can be comparable to that of the background plasma, and that the kinetic modifications of the equilibrium can be significant. The range of validity of the finite-Larmor-radius expansion and of the reduced kinetic descriptions for the beam ions in NSTX is discussed. The calculated kinetic equilibria can be used for self-consistent numerical studies of beam-ion-driven instabilities in NSTX. © 2003 American Institute of Physics.
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52.55.Jd Magnetic mirrors, gas dynamic traps
52.40.Mj Particle beam interactions in plasmas
52.25.Fi Transport properties
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.50.Gj Plasma heating by particle beams
back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

Trends in radiation production from dynamic-hohlraums driven by single and nested wire arrays

T. W. L. Sanford, R. W. Lemke, R. C. Mock, and D. L. Peterson

Phys. Plasmas 10, 3252 (2003); http://dx.doi.org/10.1063/1.1587708 (13 pages) | Cited 14 times

Online Publication Date: 18 July 2003

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The axial radiation developed primarily from the interior of an imploding dynamic hohlraum (DH) target within a Z pinch using a single array with a large number of tungsten wires is compared with that generated using a standard [Phys. Plasmas 9, 3573 (2002)] nested (outer plus inner) array on Z. Measurements indicate that a single-array with a mass (2.5 mg) near that of the combined mass of the nested-array maximizes the DH axial power. At this mass, the DH utilizing the standard nested array generates (23±15)% more axial power than that of a single array. Measurements over a range of single-array masses (2–6 mg) show a decrease in radiation power for masses above 3.5 mg. Two-dimensional radiation magnetohydrodynamic simulations, which have successfully described radial emission from targetless implosions for both single and nested-array configurations [Phys. Plasmas 6, 2178 (1999)], however, do not follow the observed trends well. This lack of tracking implies that current 2D models, which take into account the development of the magnetic Rayleigh–Taylor (RT) instability in the r–z plane, require improvements in order to provide a self-consistent description of the implosion dynamics and radiation production for DH experiments. © 2003 American Institute of Physics.
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52.57.-z Laser inertial confinement
52.55.Ez Theta pinch

Experimental study for angular distribution of the hot electrons generated by femtosecond laser interaction with solid targets

D. F. Cai, Y. Q. Gu, Z. J. Zheng, T. S. Wen, S. T. Chunyu, Z. B. Wang, and X. D. Yang

Phys. Plasmas 10, 3265 (2003); http://dx.doi.org/10.1063/1.1587709 (5 pages) | Cited 14 times

Online Publication Date: 18 July 2003

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The experimental results of angular distribution of hot electrons in the interaction of a 60 fs, 125 mJ, 800 nm, ∼ 1017 W cm−2 laser pulse with Al targets are reported. Three obvious peaks of hot electrons emission have been observed, as there is a weak normal component of the laser electric field. These emission peaks are located in the directions of the specular reflection of the laser, the target normal, and the backreflection of the laser, respectively. In the case of the P-polarized laser pulse, which has a strong normal component of the laser electric field, the peak in the backreflection of the laser disappeared, and only two obvious peaks of hot electron emissions existed. It shows that the different directions of hot electrons emission are dominated by different absorption or acceleration mechanisms. The experimental result of the hot electrons energy spectrum at the target normal shows that the effective temperature of hot electrons is about 190 keV, which is consistent with a scaling law of the resonance absorption. © 2003 American Institute of Physics.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
72.30.+q High-frequency effects; plasma effects
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
79.20.Ds Laser-beam impact phenomena
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