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Mar 2013

Volume 20, Issue 3, Articles (03xxxx)

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Phys. Plasmas 20, 032106 (2013); http://dx.doi.org/10.1063/1.4794320 (10 pages)

M. Raghunathan and R. Ganesh
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back to top Nonlinear Phenomena, Turbulence, Transport

Adiabatic trapping in coupled kinetic Alfvén-acoustic waves

H. A. Shah, W. Masood, and Z. Ali

Phys. Plasmas 20, 032301 (2013); http://dx.doi.org/10.1063/1.4794730 (6 pages)

Online Publication Date: 11 March 2013

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In the present work, we have discussed the effects of adiabatic trapping of electrons on obliquely propagating Alfvén waves in a low β plasma. Using the two potential theory and employing the Sagdeev potential approach, we have investigated the existence of arbitrary amplitude coupled kinetic Alfvén-acoustic solitary waves in both the sub and super Alfvénic cases. The results obtained have been analyzed and presented graphically and can be applied to regions of space where the low β assumption holds true.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Sb Solitons; BGK modes
95.30.Qd Magnetohydrodynamics and plasmas

Effects of plasma particle trapping on dust-acoustic solitary waves in an opposite polarity dust-plasma medium

Zulfiqar Ahmad, A. Mushtaq, and A. A. Mamun

Phys. Plasmas 20, 032302 (2013); http://dx.doi.org/10.1063/1.4794732 (9 pages)

Online Publication Date: 12 March 2013

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Dust acoustic solitary waves in a dusty plasma containing dust of opposite polarity (adiabatic positive and negative dust), non-isothermal electrons and ions (following vortex like distribution) are theoretically investigated by employing pseudo-potential approach, which is valid for arbitrary amplitude structures. The propagation of small but finite amplitude solitary structures is also examined by using the reductive perturbation method. The basic properties of large (small) amplitude solitary structures are investigated by analyzing the energy integral (modified Korteweg-de Vries equation). It is shown that the effects of dust polarity, trapping of plasma particles (electrons and ions), and temperatures of dust fluids significantly modify the basic features of the dust-acoustic solitary structures that are found to exist in such an opposite polarity dust-plasma medium. The relevance of the work in opposite polarity dust-plasma, which may occur in cometary tails, upper mesosphere, Jupiter's magnetosphere, is briefly discussed.
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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.Sb Solitons; BGK modes
94.05.Fg Solitons and solitary waves
95.30.Qd Magnetohydrodynamics and plasmas

Nonlinear interaction of kinetic Alfvén wave with fast magnetosonic wave and turbulent spectrum

K. V. Modi and R. P. Sharma

Phys. Plasmas 20, 032303 (2013); http://dx.doi.org/10.1063/1.4794834 (6 pages)

Online Publication Date: 12 March 2013

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In the present paper, authors have investigated nonlinear interaction of kinetic Alfvén wave (KAW) and fast magnetosonic wave for intermediate β-plasma (me/mi≪β≪1). Authors have developed the set of dimensionless equations in the presence of ponderomotive nonlinearity due to KAW in the dynamics of fast magnetosonic wave. Numerical simulation has been carried out to study the effect of nonlinear coupling and resulting turbulent/power spectrum for the different angles of propagation of fast magnetosonic wave applicable to solar wind at 1 AU. The localization of KAW has been found which becomes more complex as the angle of propagation of fast magnetosonic wave decreases. Results also reveal the steepening of power spectrum as the angle of propagation decreases which can be responsible for heating and acceleration of plasma particles in solar wind. Relevance of the obtained result is pointed out with observation received by Cluster spacecraft for the solar wind 1 AU.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Ra Plasma turbulence
52.50.Gj Plasma heating by particle beams
52.65.-y Plasma simulation
FREE

Landau damping in a turbulent setting

G. G. Plunk

Phys. Plasmas 20, 032304 (2013); http://dx.doi.org/10.1063/1.4794851 (6 pages)

Online Publication Date: 12 March 2013

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To address the problem of Landau damping in kinetic turbulence, we consider the forcing of the linearized Vlasov equation by a stationary random source. It is found that the time-asymptotic density response is dominated by resonant particle interactions that are synchronized with the source. The energy consumption of this response is calculated, implying an effective damping rate, which is the main result of this paper. Evaluating several cases, it is found that the effective damping rate can differ from the Landau damping rate in magnitude and also, remarkably, in sign. A limit is demonstrated in which the density and current become phase-locked, which causes the effective damping to be negligible; this result offers a fresh perspective from which to reconsider recent observations of kinetic turbulence satisfying critical balance.
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52.35.Ra Plasma turbulence
02.30.-f Function theory, analysis
52.25.Dg Plasma kinetic equations

Stochastic Lagrangian dynamics for charged flows in the E-F regions of ionosphere

Wenbo Tang and Alex Mahalov

Phys. Plasmas 20, 032305 (2013); http://dx.doi.org/10.1063/1.4794735 (11 pages)

Online Publication Date: 13 March 2013

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We develop a three-dimensional numerical model for the E-F region ionosphere and study the Lagrangian dynamics for plasma flows in this region. Our interest rests on the charge-neutral interactions and the statistics associated with stochastic Lagrangian motion. In particular, we examine the organizing mixing patterns for plasma flows due to polarized gravity wave excitations in the neutral field, using Lagrangian coherent structures (LCS). LCS objectively depict the flow topology—the extracted attractors indicate generation of ionospheric density gradients, due to accumulation of plasma. Using Lagrangian measures such as the finite-time Lyapunov exponents, we locate the Lagrangian skeletons for mixing in plasma, hence where charged fronts are expected to appear. With polarized neutral wind, we find that the corresponding plasma velocity is also polarized. Moreover, the polarized velocity alone, coupled with stochastic Lagrangian motion, may give rise to polarized density fronts in plasma. Statistics of these trajectories indicate high level of non-Gaussianity. This includes clear signatures of variance, skewness, and kurtosis of displacements taking polarized structures aligned with the gravity waves, and being anisotropic.
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94.20.wc Plasma motion; plasma convection; particle acceleration
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Fi Transport properties
94.20.dg E region
94.20.dj F region

Nonlinear compressions in merging plasma jets

S. Messer, A. Case, L. Wu, S. Brockington, and F. D. Witherspoon

Phys. Plasmas 20, 032306 (2013); http://dx.doi.org/10.1063/1.4795304 (9 pages)

Online Publication Date: 15 March 2013

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We investigate the dynamics of merging supersonic plasma jets using an analytic model. The merging structures exhibit supersonic, nonlinear compressions which may steepen into full shocks. We estimate the distance necessary to form such shocks and the resulting jump conditions. These theoretical models are compared to experimental observations and simulated dynamics. We also use those models to extrapolate behavior of the jet-merging compressions in a Plasma Jet Magneto-Inertial Fusion reactor.
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52.30.-q Plasma dynamics and flow
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Tc Shock waves and discontinuities
52.65.-y Plasma simulation
02.60.Ed Interpolation; curve fitting

Propagation of ion-acoustic solitons in an electron beam-superthermal plasma system with finite ion-temperature: Linear and fully nonlinear investigation

E. Saberian, A. Esfandyari-Kalejahi, A. Rastkar-Ebrahimzadeh, and M. Afsari-Ghazi

Phys. Plasmas 20, 032307 (2013); http://dx.doi.org/10.1063/1.4795745 (15 pages)

Online Publication Date: 19 March 2013

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The propagation of ion-acoustic (IA) solitons is studied in a plasma system, comprised of warm ions and superthermal (Kappa distributed) electrons in the presence of an electron-beam by using a hydrodynamic model. In the linear analysis, it is seen that increasing the superthermality lowers the phase speed of the IA waves. On the other hand, in a fully nonlinear investigation, the Mach number range and characteristics of IA solitons are analyzed, parametrically and numerically. It is found that the accessible region for the existence of IA solitons reduces with increasing the superthermality. However, IA solitons with both negative and positive polarities can coexist in the system. Additionally, solitary waves with both subsonic and supersonic speeds are predicted in the plasma, depending on the value of ion-temperature and the superthermality of electrons in the system. It is examined that there are upper critical values for beam parameters (i.e., density and velocity) after which, IA solitary waves could not propagate in the plasma. Furthermore, a typical interaction between IA waves and the electron-beam in the plasma is confirmed.
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52.35.Sb Solitons; BGK modes
52.40.Mj Particle beam interactions in plasmas
02.60.-x Numerical approximation and analysis
52.25.Fi Transport properties
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.)

Nonlinear interaction and parametric instability of kinetic Alfvén waves in multicomponent plasmas

J. S. Zhao, D. J. Wu, L. Yang, and J. Y. Lu

Phys. Plasmas 20, 032308 (2013); http://dx.doi.org/10.1063/1.4796054 (6 pages)

Online Publication Date: 21 March 2013

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Nonlinear couplings among kinetic Alfvén waves are investigated for a three-component plasma consisting of electrons, protons, and heavy ions. The parametric instability is investigated, and the growth rate is obtained. In the kinetic regime, the growth rate for the parallel decay instability increases with the heavy ion content, but the growth rate for the reverse decay is independent of the latter since the perpendicular wavelength is much larger than the ion gyroradius. It decreases with the heavy ion content when the perpendicular wavelength is of the order of the ion gyroradius. It is also found that in the short perpendicular wavelength limit, the growth rate is only weakly affected by the heavy ions. On the other hand, in the inertial regime, for both parallel and reverse decay cases, the growth rate decreases as the number of heavy ions becomes large.
Show PACS
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

Verification of electromagnetic fluid-kinetic hybrid electron model in global gyrokinetic particle simulation

I. Holod and Z. Lin

Phys. Plasmas 20, 032309 (2013); http://dx.doi.org/10.1063/1.4798392 (6 pages)

Online Publication Date: 26 March 2013

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The fluid-kinetic hybrid electron model is verified in global gyrokinetic particle simulation of linear electromagnetic drift-Alfvénic instabilities in tokamak. In particular, we have recovered the β-stabilization of the ion temperature gradient mode, transition to collisionless trapped electron mode, and the onset of kinetic ballooning mode as βe (ratio of electron kinetic pressure to magnetic pressure) increases.
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52.55.Fa Tokamaks, spherical tokamaks
52.65.Ww Hybrid methods
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.)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma

Impurity transport in trapped electron mode driven turbulence

A. Mollén, I. Pusztai, T. Fülöp, and S. Moradi

Phys. Plasmas 20, 032310 (2013); http://dx.doi.org/10.1063/1.4796196 (13 pages)

Online Publication Date: 28 March 2013

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Trapped electron mode turbulence is studied by gyrokinetic simulations with the GYRO code and an analytical model including the effect of a poloidally varying electrostatic potential. Its impact on radial transport of high-Z trace impurities close to the core is thoroughly investigated, and the dependence of the zero-flux impurity density gradient (peaking factor) on local plasma parameters is presented. Parameters such as ion-to-electron temperature ratio, electron temperature gradient, and main species density gradient mainly affect the impurity peaking through their impact on mode characteristics. The poloidal asymmetry, the safety factor, and magnetic shear have the strongest effect on impurity peaking, and it is shown that under certain scenarios where trapped electron modes are dominant, core accumulation of high-Z impurities can be avoided. We demonstrate that accounting for the momentum conservation property of the impurity-impurity collision operator can be important for an accurate evaluation of the impurity peaking factor.
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52.35.Ra Plasma turbulence
52.25.Vy Impurities in plasmas
52.65.Tt Gyrofluid and gyrokinetic simulations
52.25.Fi Transport properties
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.25.Xz Magnetized plasmas
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