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Apr 2007

Volume 14, Issue 4, Articles (04xxxx)

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Derivation of paleoclassical key hypothesis

J. D. Callen

Phys. Plasmas 14, 040701 (2007); http://dx.doi.org/10.1063/1.2715564 (4 pages) | Cited 9 times

Online Publication Date: 12 April 2007

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The paleoclassical model of radial electron heat transport in resistive, current-carrying toroidal plasmas is based on a key hypothesis—that electron guiding centers move and diffuse with radially localized annuli of poloidal magnetic flux. This hypothesis is shown to result from transforming the drift-kinetic-equation to poloidal flux coordinates in situations where this flux is governed by a diffusion equation and analyzing the mathematical characteristic curves (guiding center trajectories) of the resultant drift-kinetic equation on the magnetic field diffusion time scale τη ≡ a2/6Dη. These effects add a τη time-scale Fokker-Planck-type spatial diffusion operator to the drift-kinetic equation.
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52.25.Dg Plasma kinetic equations
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, field structure, etc.
52.25.Fi Transport properties
52.55.Fa Tokamaks, spherical tokamaks
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)

Excitation of macromagnetohydrodynamic mode due to multiscale interaction in a quasi-steady equilibrium formed by a balance between microturbulence and zonal flow

A. Ishizawa and N. Nakajima

Phys. Plasmas 14, 040702 (2007); http://dx.doi.org/10.1063/1.2716669 (4 pages) | Cited 21 times

Online Publication Date: 16 April 2007

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This is the first numerical simulation demonstrating that a macromagnetohydrodynamic (macro-MHD) mode is excited as a result of multi-scale interaction in a quasi-steady equilibrium formed by a balance between microturbulence and zonal flow based on a reduced two-fluid model. This simulation of a macro-MHD mode, a double tearing mode, is accomplished in a reversed shear equilibrium that includes zonal flow and turbulence due to kinetic ballooning modes. In the quasi-steady equilibrium, a macroscale fluctuation that has the same helicity as the double tearing mode is a part of the turbulence. After a certain period of time, the macro-MHD mode begins to grow. It effectively utilizes free energy of the equilibrium current density gradient and is destabilized by a positive feedback loop between zonal flow suppression and magnetic island growth. Thus, once the macro-MHD appears from the quasi-equilibrium, it continues to grow steadily. This simulation is more comparable with experimental observations of growing macro-MHD activity than earlier MHD simulations starting from linear macroinstabilities in a static equilibrium.
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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.)
52.35.Ra Plasma turbulence
52.55.Fa Tokamaks, spherical tokamaks

Self-guiding of 100 TW femtosecond laser pulses in centimeter-scale underdense plasma

L. M. Chen, H. Kotaki, K. Nakajima, J. Koga, S. V. Bulanov, T. Tajima, Y. Q. Gu, H. S. Peng, X. X. Wang, T. S. Wen, H. J. Liu, C. Y. Jiao, C. G. Zhang, X. J. Huang, Y. Guo, et al.

Phys. Plasmas 14, 040703 (2007); http://dx.doi.org/10.1063/1.2720374 (4 pages) | Cited 8 times

Online Publication Date: 20 April 2007

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An experiment for studying laser self-guiding has been carried out for the high power ultrashort pulse laser interaction with an underdense plasma slab. Formation of an extremely long plasma channel and its bending are observed when the laser pulse power is much higher than the critical power for relativistic self-focusing. The long self-guiding channel formation is accompanied by electron acceleration with a low transverse emittance and high electric current. Particle-in-cell simulations show that laser bending occurs when the accelerated electrons overtake the laser pulse and modify the refractive index in the region in front of the laser pulse.
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52.38.Hb Self-focussing, channeling, and filamentation in plasmas
52.38.Kd Laser-plasma acceleration of electrons and ions
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Fi Transport properties
52.65.Rr Particle-in-cell method

Linear and nonlinear development of oblique beam-plasma instabilities in the relativistic kinetic regime

L. Gremillet, D. Bénisti, E. Lefebvre, and A. Bret

Phys. Plasmas 14, 040704 (2007); http://dx.doi.org/10.1063/1.2714509 (4 pages) | Cited 18 times

Online Publication Date: 20 April 2007

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Collisionless beam-plasma instabilities are expected to play a crucial role during the early phase of the relativistic electron transport in the Fast Ignition scheme. This Letter presents a theoretical study of these instabilities in a two-dimensional geometry, highlighting the role of unstable modes propagating obliquely to the beam direction. The main features identified through a linearized analysis in a very general kinetic framework are examined by means of a particle-in-cell simulation. Good agreement between the two approaches is observed in the linear phase. Beam trapping is found to account for the nonlinear wave saturation.
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52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.50.Gj Plasma heating by particle beams
52.65.Rr Particle-in-cell method

Investigation of the interaction potential and thermodynamic functions of dusty plasma by measured correlation functions

V. E. Fortov, A. V. Gavrikov, O. F. Petrov, I. A. Shakhova, and V. S. Vorob’ev

Phys. Plasmas 14, 040705 (2007); http://dx.doi.org/10.1063/1.2717601 (4 pages) | Cited 8 times

Online Publication Date: 20 April 2007

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Results of investigation of the compressibility factor, compressibility, and the internal energy of dusty plasma are reported. The integral equations approach is used to calculate charge, screening radius and the interaction potential of dust particles. This approach is based on experimentally obtained pair correlation functions. It is demonstrated that states of dusty plasma structure correspond to supercritical fluid with a greater or lesser density.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.25.Kn Thermodynamics of plasmas
02.30.Rz Integral equations

On the behavior of ultraintense laser produced hot electrons in self-excited fields

T. Yabuuchi, K. Adumi, H. Habara, R. Kodama, K. Kondo, T. Tanimoto, K. A. Tanaka, Y. Sentoku, T. Matsuoka, Z. L. Chen, M. Tampo, A. L. Lei, and K. Mima

Phys. Plasmas 14, 040706 (2007); http://dx.doi.org/10.1063/1.2722303 (4 pages) | Cited 17 times

Online Publication Date: 27 April 2007

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A large number of hot electrons exceeding the Alfvén current can be produced when an ultraintense laser pulse irradiates a solid target. Self-excited extreme electrostatic and magnetic fields at the target rear could influence the electron trajectory. In order to investigate the influence, we measure the hot electrons when a plasma was created on the target rear surface in advance and observe an increase of the electron number by a factor of 2. This increase may be due to changes in the electrostatic potential formation process with the rear plasma. Using a one-dimensional particle-in-cell simulation, it is shown that the retardation in the electrostatic potential formation lengthens the gate time when electrons can escape from the target. The electron number escaping within the lengthened time window appears to be much smaller than the net produced number and is consistent with our estimation using the Alfvén limit.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Fi Transport properties
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.65.Rr Particle-in-cell method
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back to top Basic Plasma Phenomena, Waves, Instabilities

Alfvénic phenomena triggered by resonant absorption of an O-mode pulse

F. S. Tsung, G. J. Morales, and J. Tonge

Phys. Plasmas 14, 042101 (2007); http://dx.doi.org/10.1063/1.2711428 (10 pages) | Cited 3 times

Online Publication Date: 5 April 2007

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A simulation and modeling study is made of the nonlinear interaction of an electromagnetic pulse, in the O-mode polarization, with a magnetized plasma having a cross-field density gradient. For small amplitudes, the pulse propagates up to the cutoff layer where an Airy pattern develops. Beyond a certain power level, the ponderomotive force produced by the standing electromagnetic fields carves density cavities. The excess density piled up on the side of the cavities causes secondary, field-aligned plasma resonances to arise. Strong electron acceleration occurs due to the short scale of the secondary resonant fields. The fast electrons exiting the new resonant layers induce a return current system in the background plasma. This generates a packet of shear Alfvén waves of small transverse scale and increasing frequency. The results provide insight into microscopic processes associated with a recent laboratory investigation in which large-amplitude Alfvén waves have been generated upon application of high-power microwaves [ B. Van Compernolle et al., Phys. Plasmas 13, 092112 (2006) ].
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.65.Rr Particle-in-cell method

Model of grain charging in collisional plasmas accounting for collisionless layer

L. G. D’yachkov, A. G. Khrapak, S. A. Khrapak, and G. E. Morfill

Phys. Plasmas 14, 042102 (2007); http://dx.doi.org/10.1063/1.2713719 (6 pages) | Cited 14 times

Online Publication Date: 12 April 2007

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Grain charging in collision dominated plasmas is investigated. The transition from a thin collisionless region around the grain, ℓi(e)≪a, to a thick one, ℓi(e)≫a, is studied under the assumptions ℓi(e)≪λD and a≪λD, where ℓi(e) is the ion (electron) mean free path, a is the grain radius, and λD is the plasma screening length. It is also assumed that no ionization and recombination occur in the vicinity of the grain. With these assumptions, the analytical model of grain charging is constructed, the expressions for the ion and electron fluxes to the grain surface are derived, and the grain charge is obtained from their balance. The analytical results are then compared with the available experimental results. The behavior of ion and electron number densities in the vicinity of the grain is briefly discussed.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions

Vlasov-Maxwell plasma equilibria with temperature and density gradients: Weak inhomogeneity limit

C. Montagna and F. Pegoraro

Phys. Plasmas 14, 042103 (2007); http://dx.doi.org/10.1063/1.2718911 (6 pages) | Cited 3 times

Online Publication Date: 18 April 2007

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Stationary self-consistent solutions of the Vlasov-Maxwell system in a magnetized plasma (so called Vlasov equilibria) with both density and temperature gradients are investigated analytically in the limit of weak inhomogeneities. These solutions provide a simple class of self-consistent equilibria that can be used as a convenient starting point for numerical studies such as the study of the effects of temperature gradient and temperature anisotropy on the nonlinear development of reconnection instabilities in a kinetic plasma regime.
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52.25.Xz Magnetized plasmas
52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Vd Magnetic reconnection
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

Experimental and numerical analysis of the electron injection in a Malmberg-Penning trap

G. Bettega, F. Cavaliere, M. Cavenago, A. Illiberi, R. Pozzoli, and M. Romé

Phys. Plasmas 14, 042104 (2007); http://dx.doi.org/10.1063/1.2721072 (7 pages) | Cited 4 times

Online Publication Date: 25 April 2007

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The injection phase in a Malmberg-Penning trap is investigated both experimentally in the ELTRAP [ M. Amoretti et al., Rev. Sci. Instrum. 74, 3991 (2003) ] device, and numerically. The resulting plasma density distribution is studied by varying the source parameters, the external magnetic field strength, and the axial position of the external potential barrier. Space charge phenomena dominate the dynamics of the system; formation of hollow plasma columns and three-dimensional structures are observed. The processes are interpreted using a three-dimensional particle-in-cell code which solves the drift-Poisson system.
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52.40.Mj Particle beam interactions in plasmas
52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps
52.65.Rr Particle-in-cell method
52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
02.60.Lj Ordinary and partial differential equations; boundary value problems

Field statistics and correlation functions for stochastically growing waves

Iver H. Cairns, D. L. Konkolewicz, and P. A. Robinson

Phys. Plasmas 14, 042105 (2007); http://dx.doi.org/10.1063/1.2715572 (20 pages) | Cited 5 times

Online Publication Date: 26 April 2007

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Bursty waves are common in laboratory and space plasmas. This paper simulates the generation of bursty waves using stochastic differential equations, calculating the field statistics and correlation functions with and without thermal effects, linear instability, nonlinear processes, intrinsic spatiotemporal inhomogeneities (clumps), and different sampling techniques. Driven thermal waves are shown to have field statistics that agree very well with an analytic prediction (typically power-law above a low field peak near the thermal level, but whose peak can be moved to high fields with appropriate fine tuning of parameters) and are robust against changes in sampling and inclusion of clumping effects. Purely stochastically growing waves, expected to have the log normal statistics observed in multiple applications, only do so under stringent conditions and inclusion of spatiotemporal clumping effects. These conditions have similar forms to ones derived previously using analytic arguments. Deviations from a log normal can be due to sampling and clumping effects, rather than due to the nonlinear and convolution effects inferred previously. Correlation functions are predicted and observed to have an exponential decrease at small lags, with time constant equal to the inverse effective growth rate, provided stochastic effects are relatively small and sufficient averaging is possible. Extraction of the wave, stochastic, and clump parameters from observed field statistics and correlation functions appears viable. An evolutionary transition must exist between driven thermal waves and stochastically driven waves, since their field statistics have different functional forms, dependencies, and sensitivity to clump effects, but still requires identification.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.65.Pp Monte Carlo methods
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
02.50.Ey Stochastic processes

Effect of secondary electron emission on the Jeans instability in a dusty plasma

Susmita Sarkar, Banamali Roy, Saumyen Maity, Manoranjan Khan, and M. R. Gupta

Phys. Plasmas 14, 042106 (2007); http://dx.doi.org/10.1063/1.2718926 (7 pages) | Cited 2 times

Online Publication Date: 27 April 2007

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In this paper the effect of secondary electron emission on Jeans instability in a dusty plasma has been investigated. Due to secondary electron emission, dust grains may have two stable equilibrium states out of which one is negative and the other is positive. Here both cases have been considered separately. It has been shown that secondary electron emission enhances Jeans instability when equilibrium dust charge is negative. It has also been shown that growth rate of Jeans instability reduces with increasing secondary electron emission when equilibrium dust charge is positive.
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52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.27.Lw Dusty or complex plasmas; plasma crystals
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Tx Emission, absorption, and scattering of particles

Quantum dust-acoustic double layers

W. M. Moslem, P. K. Shukla, S. Ali, and R. Schlickeiser

Phys. Plasmas 14, 042107 (2007); http://dx.doi.org/10.1063/1.2719633 (8 pages) | Cited 30 times

Online Publication Date: 27 April 2007

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The quantum dust-acoustic double layers (QDADLs) are studied in an unmagnetized, collisionless quantum dusty plasma whose constituents are the electrons, ions, and negatively/positively charged dust particles. By employing the quantum hydrodynamical equations and the reductive perturbation technique, a quantum extended Korteweg–de Vries equation is derived. A steady-state double-layer solution of the latter is presented by taking into account the quantum-mechanical effects. It is numerically found that both compressive and rarefactive QDADLs can exist only for positive charged dust particles under the condition ni0/ne0<1, where ni0(ne0) is the unperturbed number density of the ions (electrons). It is further noted that the formation of the compressive and the rarefactive double layers depends on the quantum plasma parameters. The relevance of the present investigation to the dust charge impurities in laser-solid interactions is discussed. In general, this study should be useful for the diagnostics of charged dust impurities in ultrasmall microelectronic and nanoelectronic components, as well as in astrophysical objects where charged dust particles are inherently present.
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03.65.-w Quantum mechanics
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

Gyrokinetic theory and simulation of mirror instability

Hongpeng Qu, Zhihong Lin, and Liu Chen

Phys. Plasmas 14, 042108 (2007); http://dx.doi.org/10.1063/1.2721074 (7 pages) | Cited 3 times

Online Publication Date: 27 April 2007

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The finite Larmor radius (FLR) effects play an important role in determining the threshold and the growth rate of the mirror instability. In this study, a general dispersion relation of the mirror mode with FLR effects is derived by using gyrokinetic theory. It shows that both the FLR effects and the coupling to the slow sound wave are stabilizing. A gyrokinetic particle simulation code has been developed for simulation of compressible magnetic turbulence driven by the mirror instability. Results of the linear simulation of mirror mode agree well with the analytic dispersion relation.
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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.Tt Gyrofluid and gyrokinetic simulations
52.25.Dg Plasma kinetic equations
52.35.Dm Sound waves
52.35.Ra Plasma turbulence
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)

Global nonambipolar flow: Plasma confinement where all electrons are lost to one boundary and all positive ions to another boundary

S. D. Baalrud, N. Hershkowitz, and B. Longmier

Phys. Plasmas 14, 042109 (2007); http://dx.doi.org/10.1063/1.2722262 (6 pages) | Cited 12 times

Online Publication Date: 30 April 2007

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A new mode of plasma confinement is demonstrated in which essentially all positive ions leave the plasma to only one boundary while essentially all electrons are lost to a different boundary. Sheaths near the plasma boundaries are entirely responsible for this global nonambipolar flow. The bulk plasma remains quasineutral and unperturbed even when all electrons are lost to only one, physically small, location. A necessary condition for global nonambipolar flow depends on the ratio of electron collection area to ion collection area. The plasma electron temperature is significantly higher in the global nonambipolar mode than in the typical ambipolar mode due to a relative increase in confinement of high-energy electrons and a relative decrease in confinement of low-energy electrons.
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52.30.-q Plasma dynamics and flow
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, field structure, etc.
52.40.Hf Plasma-material interactions; boundary layer effects
52.40.Kh Plasma sheaths
52.25.Fi Transport properties
back to top Nonlinear Phenomena, Turbulence, Transport

Fluid simulations of turbulent impurity transport

N. Dubuit, X. Garbet, T. Parisot, R. Guirlet, and C. Bourdelle

Phys. Plasmas 14, 042301 (2007); http://dx.doi.org/10.1063/1.2710461 (8 pages) | Cited 25 times

Online Publication Date: 5 April 2007

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Impurity transport in tokamak plasmas is studied with a fluid turbulence code, which has been upgraded to implement two ion species and electrons. The (fixed-flux) simulations are compared to the predictions of a quasilinear model. These simulations mostly agree with quasilinear estimates; they indicate that a turbulent impurity pinch exists. Moreover, this pinch is found to be dominated by curvature terms, as thermodiffusion pinches are found to decrease as 1/Z and observed parallel velocity effects remain weak. The sign of the pinch is also investigated.
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52.25.Fi Transport properties
52.25.Vy Impurities in plasmas
52.35.Ra Plasma turbulence
52.65.Kj Magnetohydrodynamic and fluid equation
52.55.Fa Tokamaks, spherical tokamaks
52.55.Ez Theta pinch

Nonlinear quantum dust acoustic waves in nonuniform complex quantum dusty plasma

W. F. El-Taibany and Miki Wadati

Phys. Plasmas 14, 042302 (2007); http://dx.doi.org/10.1063/1.2717883 (9 pages) | Cited 49 times

Online Publication Date: 5 April 2007

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The quantum hydrodynamic model for plasmas is employed to study the dynamics of the nonlinear quantum dust acoustic (QDA) wave in a nonuniform quantum dusty plasma (QDP). Through the reductive perturbation technique, it is shown that the quantum hydrodynamical basic equations describing the nonlinear QDA waves yield a modified Korteweg-de Veries equation with slowly varying coefficients in the system inhomogeneity. Applying generalized expansion method, it is found that the system admits only rarefactive solitons. The properties of the solitons such as the velocity, the amplitude and the width of the nonlinear QDA waves are analyzed using appropriate choice for initial ion and electron density numbers. For the homogeneous QDP, no critical value is found. Because of the system inhomogeneity, a new criticality is found forcing with the usage of new stretching coordinates. A higher evolution equation with third-order nonlinearity is derived at the critical values. The solution of the latter equation admits rarefactive shock wave attached with an amplitude factor. The present investigations should be useful for researches on astrophysical plasmas as well as for ultra small micro- and nano-electronic devices.
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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.Dm Sound waves
52.27.Lw Dusty or complex plasmas; plasma crystals
52.35.Sb Solitons; BGK modes
52.35.Tc Shock waves and discontinuities
52.25.Fi Transport properties

Heating of ions by low-frequency Alfven waves

Quanming Lu and Xing Li

Phys. Plasmas 14, 042303 (2007); http://dx.doi.org/10.1063/1.2715569 (6 pages) | Cited 12 times

Online Publication Date: 9 April 2007

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This paper reports a new physical mechanism that enables the heating of ions by a low-frequency parallel propagating Alfven wave of finite amplitude in a low beta plasma. The heating does not rely on ion cyclotron resonance. The process has two stages: First, ions, whose initial average velocity is zero, are picked up in the transverse direction by the Alfven wave and obtain an average transverse velocity. Second, at a given location the parallel thermal motions of ions produce phase differences (randomization) between ions leading to the heating of ions. The randomization (or heating) process saturates when phase differences are sufficiently large. The time scale over which ions are significantly heated is ∼ π/(kvth) (vth is the initial ion thermal speed and k is the wave number). The heating is dominant in the perpendicular (to the background magnetic field) direction. Subsequently, a large ion temperature anisotropy is produced. During the heating process, ions are also accelerated in the parallel direction and obtain a bulk flow speed along the background magnetic field.
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52.50.Sw Plasma heating by microwaves; ECR, LH, collisional heating
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.25.Fi Transport properties
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

Nonlinear plasma response to a slowly varying electrostatic wave, and application to stimulated Raman scattering

Didier Bénisti and Laurent Gremillet

Phys. Plasmas 14, 042304 (2007); http://dx.doi.org/10.1063/1.2711819 (22 pages) | Cited 25 times

Online Publication Date: 16 April 2007

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The nonlinear electronic susceptibility induced by an electrostatic wave slowly varying in space and time, which is the key parameter for the kinetic modeling of stimulated Raman scattering (SRS), is derived analytically. When calculating the real part of the susceptibility, by making the adiabatic approximation, account is taken of the amplitude dependence of the wave frequency. Then, the “loss of resonance” of a plasma wave is found to occur at much larger amplitudes than has been predicted by Rose and Russel [ H. A. Rose and D. A. Russell, Phys. Plasmas 11, 4784 (2001) ] using the constant-frequency approximation. The imaginary part of the susceptibility, from which is deduced the Landau damping rate of the plasma wave, is derived using two different approaches (perturbative or not) depending on the wave amplitude. It is shown to be a nonlocal function of the wave amplitude, which underlines the importance of interspeckle interactions in SRS.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.38.Bv Rayleigh scattering; stimulated Brillouin and Raman scattering
52.38.-r Laser-plasma interactions
45.20.Jj Lagrangian and Hamiltonian mechanics

On the relation between secondary and modulational instabilities

D. Strintzi and F. Jenko

Phys. Plasmas 14, 042305 (2007); http://dx.doi.org/10.1063/1.2720370 (6 pages) | Cited 2 times

Online Publication Date: 24 April 2007

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The nonlinear saturation of microinstabilities in toroidal magnetoplasmas is sometimes discussed in the framework of secondary instability theory. At the same time, it has been proposed that the nonlinear generation of zonal flows—which are often responsible for turbulence control—can be explained in terms of modulational instabilities. The question of how these two approaches are connected to each other is addressed.
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52.35.Ra Plasma turbulence
52.35.Kt Drift waves

Intrinsic rotation and electric field shear

Ö. D. Gürcan, P. H. Diamond, T. S. Hahm, and R. Singh

Phys. Plasmas 14, 042306 (2007); http://dx.doi.org/10.1063/1.2717891 (17 pages) | Cited 68 times

Online Publication Date: 26 April 2007

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A novel mechanism for the generation and amplification of intrinsic rotation at the low-mode to high-mode transition is presented. The mechanism is one where the net parallel flow is accelerated by turbulence. A preferential direction of acceleration results from the breaking of k‖→−k‖ symmetry by sheared E×B flow. It is shown that the equilibrium pressure gradient contributes a piece of the parallel Reynolds stress, which is nonzero for vanishing parallel flow, and so can accelerate the plasma, driving net intrinsic rotation. Rotation drive, transport, and fluctuation dynamics are treated self-consistently.
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52.30.-q Plasma dynamics and flow
52.35.Ra Plasma turbulence
52.25.Fi Transport properties
52.25.Gj Fluctuation and chaos phenomena

Wave induced barrier transparency and melting of quasi-crystalline structures in two dimensional plasma turbulence

Amita Das

Phys. Plasmas 14, 042307 (2007); http://dx.doi.org/10.1063/1.2718927 (10 pages)

Online Publication Date: 27 April 2007

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The conservation of energy and enstrophy in two dimensional inviscid hydrodynamics leads to dual cascade behavior. The energy cascades towards long scales and the enstrophy is transferred to shorter scales. The interplay of these dynamical processes leads to self organization and formation of coherent patterns in the two dimensional hydrodynamic turbulence. It was shown by Kukharkin et al. [Phys. Rev. Lett. 25, 2486 (1995)] that this process of self organization occurs in an even more interesting fashion in the Hasegawa Mima (HM) equation [ Phys. Fluids 21, 21 (1978) ] This equation is a generalization of the two dimensional Navier Stokes hydrodynamics model in which there is a characteristic natural scale in the system (e.g., Larmor radius in the drift wave context). Kukharkin et al. observed that this scale acts as a barrier in the energy cascade, such that the cascade rate at the longer wavelength side of the barrier is smaller. This work has also shown that the accumulation of energy around the intrinsic scale leads to the formation of quasi-crystalline patterns. In the present paper it has been demonstrated that the presence of wave excitations leads to an increased cascade towards longer scales past the natural length scale barrier. It has also been demonstrated that wave excitations lead to the melting of quasi-crystalline structures. Another intriguing but interesting observation is that even though the faster cascade is induced by waves arising through an anisotropic inhomogeneity in one of the plasma parameters, the spectrum of the fluctuations continues to remain predominantly isotropic. A physical understanding of the observations is provided by illustrating a close connection between the Kelvin–Helmholtz destabilization of shear flows and the phenomenon of inverse cascade in 2D fluid flows.
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52.35.Ra Plasma turbulence
52.35.We Plasma vorticity
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.Kt Drift waves
52.25.Gj Fluctuation and chaos phenomena

Formulation of the relativistic moment implicit particle-in-cell method

Koichi Noguchi, Cesare Tronci, Gianluca Zuccaro, and Giovanni Lapenta

Phys. Plasmas 14, 042308 (2007); http://dx.doi.org/10.1063/1.2721083 (11 pages) | Cited 7 times

Online Publication Date: 27 April 2007

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A new formulation is presented for the implicit moment method applied to the time-dependent relativistic Vlasov-Maxwell system. The new approach is based on a specific formulation of the implicit moment method that allows us to retain the same formalism that is valid in the classical case despite the formidable complication introduced by the nonlinear nature of the relativistic equations of motion. To demonstrate the validity of the new formulation, an implicit finite difference algorithm is developed to solve the Maxwell’s equations and equations of motion. A number of benchmark problems are run: two stream instability, ion acoustic wave damping, Weibel instability, and Poynting flux acceleration. The numerical results are all in agreement with analytical solutions.
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52.27.Ny Relativistic plasmas
52.65.Rr Particle-in-cell method
52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

Variational approach for the quantum Zakharov system

F. Haas

Phys. Plasmas 14, 042309 (2007); http://dx.doi.org/10.1063/1.2722271 (6 pages) | Cited 15 times

Online Publication Date: 30 April 2007

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The quantum Zakharov system is described in terms of a Lagrangian formalism. A time-dependent Gaussian trial function approach for the envelope electric field and the low-frequency part of the density fluctuation leads to a coupled, nonlinear system of ordinary differential equations. In the semiclassical case, linear stability analysis of this dynamical system shows a destabilizing role played by quantum effects. Arbitrary values of the quantum effects are also considered, yielding the ultimate destruction of the localized, Gaussian trial solution. Numerical simulations are shown for both the semiclassical and the full quantum cases.
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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.Sb Solitons; BGK modes
03.65.-w Quantum mechanics
back to top Magnetically Confined Plasmas, Heating, Confinement

Gyrokinetic analysis of linear microinstabilities for the stellarator Wendelstein 7-X

P. Xanthopoulos and F. Jenko

Phys. Plasmas 14, 042501 (2007); http://dx.doi.org/10.1063/1.2714328 (11 pages) | Cited 5 times

Online Publication Date: 10 April 2007

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A linear collisionless gyrokinetic investigation of ion temperature gradient (ITG) modes—considering both adiabatic and full electron dynamics—and trapped electron modes (TEMs) is presented for the stellarator Wendelstein 7-X (W7-X) [ G. Grieger et al., Plasma Physics and Controlled Nuclear Fusion Research 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 525 ]. The study of ITG modes reveals that in W7-X, microinstabilities of distinct character coexist. The effect of changes in the density gradient and temperature ratio is discussed. Substantial differences with respect to the axisymmetric geometry appear in W7-X, concerning the relative separation of regions with a large fraction of helically trapped particles and those of pronounced bad curvature. For both ITG modes and TEMs, the dependence of their linear growth rates on the background gradients is studied along with their parallel mode structure.
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52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.55.Jd Magnetic mirrors, gas dynamic traps
52.25.Fi Transport properties
52.65.Tt Gyrofluid and gyrokinetic simulations
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
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