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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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Measurement of energetic-particle-driven core magnetic fluctuations and induced fast-ion transport

L. Lin, W. X. Ding, D. L. Brower, J. J. Koliner, S. Eilerman, J. A. Reusch, J. K. Anderson, M. D. Nornberg, J. S. Sarff, J. Waksman, and D. Liu

Phys. Plasmas 20, 030701 (2013); http://dx.doi.org/10.1063/1.4798397 (4 pages) | Cited 1 time

Online Publication Date: 22 March 2013

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Internal fluctuations arising from energetic-particle-driven instabilities, including both density and radial magnetic field, are measured in a reversed-field-pinch plasma. The fluctuations peak near the core where fast ions reside and shift outward along the major radius as the instability transits from the n = 5 to n = 4 mode. During this transition, strong nonlinear three-wave interaction among multiple modes accompanied by enhanced fast-ion transport is observed.
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52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.58.Lq Z-pinches, plasma focus, and other pinch devices
52.70.Nc Particle measurements
52.25.Fi Transport properties
52.25.Gj Fluctuation and chaos phenomena
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
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back to top Basic Plasma Phenomena, Waves, Instabilities

Linear mode conversion of Langmuir/z-mode waves to radiation: Scalings of conversion efficiencies and propagation angles with temperature and magnetic field orientation

F. Schleyer, Iver H. Cairns, and E.-H. Kim

Phys. Plasmas 20, 032101 (2013); http://dx.doi.org/10.1063/1.4793726 (11 pages)

Online Publication Date: 1 March 2013

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Linear mode conversion (LMC) is the linear transfer of energy from one wave mode to another in an inhomogeneous plasma. It is relevant to laboratory plasmas and multiple solar system radio emissions, such as continuum radiation from planetary magnetospheres and type II and III radio bursts from the solar corona and solar wind. This paper simulates LMC of waves defined by warm, magnetized fluid theory, specifically the conversion of Langmuir/z-mode waves to electromagnetic (EM) radiation. The primary focus is the calculation of the energy and power conversion efficiencies for LMC as functions of the angle of incidence θ of the Langmuir/z-mode wave, temperature β = Te/mec2, adiabatic index γ, and orientation angle ϕ between the ambient density gradient ∇N0 and ambient magnetic field B0 in a warm, unmagnetized plasma. The ratio of these efficiencies is found to agree well as a function of θ, γ, and β with an analytical relation that depends on the group speeds of the Langmuir/z and EM wave modes. The results demonstrate that the energy conversion efficiency ϵ is strongly dependent on γβ, ϕ and θ, with ϵ∝(γβ)1/2 and θ∝(γβ)1/2. The power conversion efficiency ϵp, on the other hand, is independent of γβ but does vary significantly with θ and ϕ. The efficiencies are shown to be maximum for approximately perpendicular density gradients (ϕ ≈ 90°) and minimal for parallel orientation (ϕ = 0°) and both the energy and power conversion efficiencies peak at the same θ.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.65.Kj Magnetohydrodynamic and fluid equation
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.65.-y Plasma simulation

Magnetorotational instability in plasmas with mobile dust grains

Haijun Ren, Jintao Cao, Ding Li, and Paul K. Chu

Phys. Plasmas 20, 032102 (2013); http://dx.doi.org/10.1063/1.4794342 (7 pages)

Online Publication Date: 4 March 2013

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The magnetorotational instability of dusty plasmas is investigated using the multi-fluid model and the general dispersion relation is derived based on local approximation. The dust grains are found to play an important role in the dispersion relation in the low-frequency mode and exhibit destabilizing effects on the plasma. Both the instability criterion and growth rate are affected significantly by the dust and when the dust is heavy enough to be unperturbed, the reduced dispersion relations are obtained. The instability criteria show that the dust grains have stabilizing effects on the instability when the rotation frequency decreases outwards and conversely lead to destabilizing effects when the rotation frequency increases outwards. The results are relevant to accession and protoplanetary disks.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.27.Lw Dusty or complex plasmas; plasma crystals

Ion heating and short wavelength fluctuations in a helicon plasma source

E. E. Scime, J. Carr, Jr., M. Galante, R. M. Magee, and R. Hardin

Phys. Plasmas 20, 032103 (2013); http://dx.doi.org/10.1063/1.4794351 (10 pages)

Online Publication Date: 4 March 2013

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For typical helicon source parameters, the driving antenna can couple to two plasma modes; the weakly damped “helicon” wave, and the strongly damped, short wavelength, slow wave. Here, we present direct measurements, obtained with two different techniques, of few hundred kHz, short wavelength fluctuations that are parametrically driven by the primary antenna and localized to the edge of the plasma. The short wavelength fluctuations appear for plasma source parameters such that the driving frequency is approximately equal to the lower hybrid frequency. Measurements of the steady-state ion temperature and fluctuation amplitude radial profiles suggest that the anomalously high ion temperatures observed at the edge of helicon sources result from damping of the short wavelength fluctuations. Additional measurements of the time evolution of the ion temperature and fluctuation profiles in pulsed helicon source plasmas support the same conclusion.
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52.50.Dg Plasma sources
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.25.-b Plasma properties
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.40.Hf Plasma-material interactions; boundary layer effects

Plasma equilibrium in a semiclassical plasma due to non-resonant wave particle interactions

Anirban Bose and M. S. Janaki

Phys. Plasmas 20, 032104 (2013); http://dx.doi.org/10.1063/1.4794279 (5 pages)

Online Publication Date: 11 March 2013

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A nonresonant perturbative approach has been utilized to probe the modification of the equilibrium plasma distribution function due to plasma interaction with externally launched high-frequency large-amplitude RF waves in the presence of quantum effects. The quantum distribution function from the complete Wigner equation has been obtained for a high-frequency wave with constant amplitude. For waves with weak spatial or temporal modulation, the equilibrium distribution function has been obtained by solving the Wigner equation as an initial or boundary-value problem and retaining only lowest-order quantum effects. In the dipole approximation, a higher order diffusion has been identified in addition to quantum modified ponderomotive and quasilinear diffusion effects. Additional terms of the Wigner equation give the impression of higher order diffusion effects in the system.
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
02.50.Ng Distribution theory and Monte Carlo studies
02.60.Lj Ordinary and partial differential equations; boundary value problems
52.25.Fi Transport properties

Low-frequency electromagnetic field in a Wigner crystal

Anton Stupka

Phys. Plasmas 20, 032105 (2013); http://dx.doi.org/10.1063/1.4794960 (3 pages)

Online Publication Date: 11 March 2013

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Long-wave low-frequency oscillations are described in a Wigner crystal by generalization of the reverse continuum model for the case of electronic lattice. The internal self-consistent long-wave electromagnetic field is used to describe the collective motions in the system. The eigenvectors and eigenvalues of the obtained system of equations are derived. The velocities of longitudinal and transversal sound waves are found.
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71.45.-d Collective effects
62.65.+k Acoustical properties of solids
02.10.Ud Linear algebra

Nonlinear Landau damping and formation of Bernstein-Greene-Kruskal structures for plasmas with q-nonextensive velocity distributions

M. Raghunathan and R. Ganesh

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

Online Publication Date: 12 March 2013

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In the past, long-time evolution of an initial perturbation in collisionless Maxwellian plasma (q = 1) has been simulated numerically. The controversy over the nonlinear fate of such electrostatic perturbations was resolved by Manfredi [Phys. Rev. Lett. 79, 2815–2818 (1997)] using long-time simulations up to t = 1600ωp−1. The oscillations were found to continue indefinitely leading to Bernstein-Greene-Kruskal (BGK)-like phase-space vortices (from here on referred as “BGK structures”). Using a newly developed, high resolution 1D Vlasov-Poisson solver based on piecewise-parabolic method (PPM) advection scheme, we investigate the nonlinear Landau damping in 1D plasma described by toy q-distributions for long times, up to t = 3000ωp−1. We show that BGK structures are found only for a certain range of q-values around q = 1. Beyond this window, for the generic parameters, no BGK structures were observed. We observe that for values of q<1 where velocity distributions have long tails, strong Landau damping inhibits the formation of BGK structures. On the other hand, for q>1 where distribution has a sharp fall in velocity, the formation of BGK structures is rendered difficult due to high wave number damping imposed by the steep velocity profile, which had not been previously reported. Wherever relevant, we compare our results with past work.
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52.65.Ff Fokker-Planck and Vlasov equation
52.25.Dg Plasma kinetic equations
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.We Plasma vorticity

Electron and ion kinetic effects on non-linearly driven electron plasma and ion acoustic waves

R. L. Berger, S. Brunner, T. Chapman, L. Divol, C. H. Still, and E. J. Valeo

Phys. Plasmas 20, 032107 (2013); http://dx.doi.org/10.1063/1.4794346 (30 pages)

Online Publication Date: 13 March 2013

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Fully non-linear kinetic simulations of electron plasma and ion acoustic waves (IAWs) have been carried out with a new multi-species, parallelized Vlasov code. The numerical implementation of the Vlasov model and the methods used to compute the wave frequency are described in detail. For the first time, the nonlinear frequency of IAWs, combining the contributions from electron and ion kinetic effects and from harmonic generation, has been calculated and compared to Vlasov results. Excellent agreement of theory with simulation results is shown at all amplitudes, harmonic generation being an essential component at large amplitudes. For IAWs, the positive frequency shift from trapped electrons is confirmed and is dominant for the effective electron-to-ion temperature ratio, Z Te/Ti ≳ 10 with Z as the charge state. Furthermore, numerical results demonstrate unambiguously the dependence [R. L. Dewar, Phys. Fluids 15, 712 (1972)] of the kinetic shifts on details of the distribution of the trapped particles, which depends in turn on the conditions under which the waves were generated. The trapped particle fractions and energy distributions are derived and, upon inclusion of harmonic effects, shown to agree with the simulation results, completing a consistent picture. Fluid models of the wave evolution are considered but prove unable to capture essential details of the kinetic simulations. Detrapping by collisions and sideloss is also discussed.
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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.-y Plasma simulation
52.65.Ff Fokker-Planck and Vlasov equation
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Fi Transport properties

A simplified approach to calculate atomic partition functions in plasmas

Giuliano D'Ammando, Gianpiero Colonna, and Mario Capitelli

Phys. Plasmas 20, 032108 (2013); http://dx.doi.org/10.1063/1.4794286 (7 pages)

Online Publication Date: 15 March 2013

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A simplified method to calculate the electronic partition functions and the corresponding thermodynamic properties of atomic species is presented and applied to C(I) up to C(VI) ions. The method consists in reducing the complex structure of an atom to three lumped levels. The ground level of the lumped model describes the ground term of the real atom, while the second lumped level represents the low lying states and the last one groups all the other atomic levels. It is also shown that for the purpose of thermodynamic function calculation, the energy and the statistical weight of the upper lumped level, describing high-lying excited atomic states, can be satisfactorily approximated by an analytic hydrogenlike formula. The results of the simplified method are in good agreement with those obtained by direct summation over a complete set (i.e., including all possible terms and configurations below a given cutoff energy) of atomic energy levels. The method can be generalized to include more lumped levels in order to improve the accuracy.
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52.25.Kn Thermodynamics of plasmas

Lifting particle coordinate changes of magnetic moment type to Vlasov-Maxwell Hamiltonian dynamics

P. J. Morrison, M. Vittot, and L. de Guillebon

Phys. Plasmas 20, 032109 (2013); http://dx.doi.org/10.1063/1.4794828 (9 pages)

Online Publication Date: 18 March 2013

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Techniques for coordinate changes that depend on both dependent and independent variables are developed and applied to the Maxwell-Vlasov Hamiltonian theory. Particle coordinate changes with a new velocity variable dependent on the magnetic field, with spatial coordinates unchanged, are lifted to the field theoretic level, by transforming the noncanonical Poisson bracket and Hamiltonian structure of the Vlasov-Maxwell dynamics. Several examples are given including magnetic coordinates, where the velocity is decomposed into components parallel and perpendicular to the local magnetic field, and the case of spherical velocity coordinates. An example of the lifting procedure is performed to obtain a simplified version of gyrokinetics, where the magnetic moment is used as a coordinate and the dynamics is reduced by elimination of the electric field energy in the Hamiltonian.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
02.30.Jr Partial differential equations

Laboratory studies of the dynamic of resonance cones formation in magnetized plasmas

V. V. Nazarov, M. V. Starodubtsev, and A. V. Kostrov

Phys. Plasmas 20, 032110 (2013); http://dx.doi.org/10.1063/1.4794965 (10 pages)

Online Publication Date: 18 March 2013

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The paper is devoted to experimental studies of formation of resonance cones in magnetized plasmas by pulsed RF source in the lower-hybrid (whistler) and the upper-hybrid frequency ranges. It is shown that in both frequency ranges, resonance cones exhibit similar dynamics after switching-on the RF source: at first, wide maxima of radiation are formed in non-resonance directions, which then become narrower, with their direction approaching the resonance one. While the resonance cones are being formed, one observes a fine structure in the form of secondary radiation maxima. It is shown that the characteristic formation time of stationary resonance cones is determined by the minimal value of the group velocity of the quasi-electrostatic waves excited by the antenna. In the low-temperature plasma, this value is limited in the lower-hybrid frequency range by the spatial spectrum of the emitting antenna and in the upper-hybrid range, by the effects of spatial plasma dispersion.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Dg Plasma sources
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.25.Xz Magnetized plasmas

Waves generated in the plasma plume of helicon magnetic nozzle

Nagendra Singh, Sathyanarayan Rao, and Praveen Ranganath

Phys. Plasmas 20, 032111 (2013); http://dx.doi.org/10.1063/1.4795734 (7 pages)

Online Publication Date: 18 March 2013

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Experimental measurements have shown that the plasma plume created in a helicon plasma device contains a conical structure in the plasma density and a U-shaped double layer (US-DL) tightly confined near the throat where plasma begins to expand from the source. Recently reported two-dimensional particle-in-cell simulations verified these density and US-DL features of the plasma plume. Simulations also showed that the plasma in the plume develops non-thermal feature consisting of radial ion beams with large densities near the conical surface of the density structure. The plasma waves that are generated by the radial ion beams affecting the structure of the plasma plume are studied here. We find that most intense waves persist in the high-density regions of the conical density structure, where the transversely accelerated ions in the radial electric fields in the plume are reflected setting up counter-streaming. The waves generated are primarily ion Bernstein modes. The nonlinear evolution of the waves leads to magnetic field-aligned striations in the fields and the plasma near the conical surface of the density structure.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.50.Gj Plasma heating by particle beams
52.70.-m Plasma diagnostic techniques and instrumentation
52.75.-d Plasma devices
52.25.-b Plasma properties

Modified Korteweg-de Vries soliton reflection in a magnetized plasma with dust grains and trapped electrons

Ravinder Kumar and Hitendra K. Malik

Phys. Plasmas 20, 032112 (2013); http://dx.doi.org/10.1063/1.4795738 (6 pages)

Online Publication Date: 19 March 2013

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This article aims at studying the reflection of solitons in an inhomogeneous magnetized warm plasma having dust grains with positive or negative charge and trapped electrons (low temperature nonisothermal electrons). In order to study the soliton reflection, a coupled modified Korteweg-de Vries equation is derived and solved along with the use of incident soliton solution. The expressions for the reflected soliton amplitude, width, and reflection coefficient are obtained, and examined under different parameter regimes. The combined effect of the dust grain density with their charge polarity and trapping of the electrons is largely studied on the soliton reflection characteristics under the influence of magnetic field.
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52.35.Sb Solitons; BGK modes
02.30.Hq Ordinary differential equations
52.25.Xz Magnetized plasmas
52.27.Lw Dusty or complex plasmas; plasma crystals

Effects of the background plasma temperature on the current filamentation instability

Qing Jia, Hong-bo Cai, Wei-wu Wang, Shao-ping Zhu, Z. M. Sheng, and X. T. He

Phys. Plasmas 20, 032113 (2013); http://dx.doi.org/10.1063/1.4796052 (6 pages)

Online Publication Date: 25 March 2013

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The effects of thermal anisotropy of background plasma on the current-filamentation instability (CFI) in an asymmetric counterstreaming system are investigated with a fully relativistic kinetic model. It is found that both the temperature and the thermal anisotropy of the background plasma play important roles in the development of the CFI. It is also pointed out that the thermal anisotropy of the background plasma dominates over the space charge effect in suppressing the CFI. A parametric study of the CFI is presented in the context of fast ignition. A new way to suppress CFI and its detrimental effects on the fast electron beam divergence has been proposed. The results of the analytical estimations are verified by 2D3V particle-in-cell simulations.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.25.-b Plasma properties
52.25.Kn Thermodynamics of plasmas
52.65.Rr Particle-in-cell method
52.40.-w Plasma interactions (nonlaser)
52.25.Dg Plasma kinetic equations

Resistive magnetohydrodynamic model for cylindrical plasma expansion in a magnetic field

H. B. Nersisyan, K. A. Sargsyan, D. A. Osipyan, and M. V. Sargsyan

Phys. Plasmas 20, 032114 (2013); http://dx.doi.org/10.1063/1.4798398 (12 pages)

Online Publication Date: 26 March 2013

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The study of hot plasma expansion in a magnetic field is of interest for many laboratory and astrophysical applications. In this paper, an exactly solvable analytical model is proposed for an expanding resistive plasma in an external magnetic field in the regime in which the magnetic field does not perturb the plasma motion. The model is based on a class of exact solutions for the purely radial expansion of the plasma in the absence of a magnetic field. This approximation permits the reduction of the electromagnetic problem to consideration of a diffusion equation for the magnetic field. Explicit solutions are derived for a resistive cylindrical plasma expanding into a uniform ambient magnetic field. Some numerical examples related to the laser-produced plasma experiments are presented.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
02.60.-x Numerical approximation and analysis
52.25.Fi Transport properties

The mixed Wentzel–Kramers–Brillouin-full-wave approach and its application to lower hybrid wave propagation and absorption

Z. X. Lu, F. Zonca, and A. Cardinali

Phys. Plasmas 20, 032115 (2013); http://dx.doi.org/10.1063/1.4798408 (13 pages)

Online Publication Date: 28 March 2013

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The mixed Wentzel–Kramers–Brillouin (WKB)-full-wave approach for the calculation of the 2D mode structure in tokamak plasmas is further developed based on our previous work [A. Cardinali and F. Zonca, Phys. Plasmas 10, 4199 (2003) and Z. X. Lu et al., Phys. Plasmas 19, 042104 (2012)]. A new scheme for theoretical analysis and numerical implementation of the mixed WKB-full-wave approach is formulated, based on scale separation and asymptotic analysis. Besides its capability to efficiently investigate the initial value problem for 2D mode structures and linear stability, in this work, the mixed WKB-full-wave approach is extended to the investigation of radio frequency wave propagation and absorption, e.g., lower hybrid waves. As a novel method, its comparison with other approaches, e.g., WKB and beam tracing methods, is discussed. Its application to lower hybrid wave propagation in concentric circular tokamak plasmas using typical FTU discharge parameters is also demonstrated.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.55.Fa Tokamaks, spherical tokamaks
52.55.Jd Magnetic mirrors, gas dynamic traps
02.30.-f Function theory, analysis
04.20.Ex Initial value problem, existence and uniqueness of solutions

Unified one-dimensional model of bounded plasma with nonzero ion temperature in a broad pressure range

J. H. Palacio Mizrahi, V. Tz. Gurovich, and Ya. E. Krasik

Phys. Plasmas 20, 032116 (2013); http://dx.doi.org/10.1063/1.4798401 (10 pages)

Online Publication Date: 29 March 2013

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A one-dimensional model for steady state plasmas bounded either between large parallel walls, or by a cylinder or a sphere, valid in a wide range of gas pressures, is considered. The model includes nonzero ion temperature, inertial terms in the ion momentum equations, and allows one to calculate the plasma electron temperature and ion current density reaching the wall, as well as the spatial distributions of the ion fluid velocity, plasma density, and plasma potential in the plasma bulk. In addition, the effect of electron inertia is analyzed. The model includes as particular cases several earlier models that were based on a similar set of differential equations, but that are restricted to a specific pressure regime (low, intermediate, or high). Analytical solution is found in planar geometry, and numerical solution is given in cylindrical and spherical geometry. The results obtained are compared with those of earlier models and the differences are analyzed.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.65.-y Plasma simulation
02.30.Hq Ordinary differential equations
02.60.Cb Numerical simulation; solution of equations
52.25.-b Plasma properties

Kelvin-Helmholtz instability in a current-vortex sheet at a 3D magnetic null

P. F. Wyper and D. I. Pontin

Phys. Plasmas 20, 032117 (2013); http://dx.doi.org/10.1063/1.4798516 (12 pages) | Cited 1 time

Online Publication Date: 29 March 2013

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We report here, for the first time, an observed instability of a Kelvin-Helmholtz nature occurring in a fully three-dimensional (3D) current-vortex sheet at the fan plane of a 3D magnetic null point. The current-vortex layer forms self-consistently in response to foot point driving around the spine lines of the null. The layer first becomes unstable at an intermediate distance from the null point, with the instability being characterized by a rippling of the fan surface and a filamentation of the current density and vorticity in the shear layer. Owing to the 3D geometry of the shear layer, a branching of the current filaments and vortices is observed. The instability results in a mixing of plasma between the two topologically distinct regions of magnetic flux on either side of the fan separatrix surface, as flux is reconnected across this surface. We make a preliminary investigation of the scaling of the system with the dissipation parameters. Our results indicate that the fan plane separatrix surface is an ideal candidate for the formation of current-vortex sheets in complex magnetic fields and, therefore, the enhanced heating and connectivity change associated with the instabilities of such layers.
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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.Vd Magnetic reconnection
52.35.We Plasma vorticity
52.25.Fi Transport properties
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

Analysis of photonic band gap in dispersive properties of tunable three-dimensional photonic crystals doped by magnetized plasma

Hai-Feng Zhang, Shao-Bin Liu, Huan Yang, and Xiang-Kun Kong

Phys. Plasmas 20, 032118 (2013); http://dx.doi.org/10.1063/1.4798523 (15 pages)

Online Publication Date: 29 March 2013

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In this paper, the magnetooptical effects in dispersive properties for two types of three-dimensional magnetized plasma photonic crystals (MPPCs) containing homogeneous dielectric and magnetized plasma with diamond lattices are theoretically investigated for electromagnetic (EM) wave based on plane wave expansion (PWE) method, as incidence EM wave vector is parallel to the external magnetic field. The equations for two types of MPPCs with diamond lattices (dielectric spheres immersed in magnetized plasma background or vice versa) are theoretically deduced. The influences of dielectric constant, plasma collision frequency, filling factor, the external magnetic field, and plasma frequency on the dispersive properties for both types of structures are studied in detail, respectively, and some corresponding physical explanations are also given. From the numerical results, it has been shown that the photonic band gaps (PBGs) for both types of MPPCs can be manipulated by plasma frequency, filling factor, the external magnetic field, and the relative dielectric constant of dielectric, respectively. Especially, the external magnetic field can enlarge the PBG for type-2 structure (plasma spheres immersed in dielectric background). However, the plasma collision frequency has no effect on the dispersive properties of two types of three-dimensional MPPCs. The locations of flatbands regions for both types of structures cannot be tuned by any parameters except for plasma frequency and the external magnetic field. The analytical results may be informative and of technical use to design the MPPCs devices.
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52.25.Mq Dielectric properties
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
61.66.Bi Elemental solids
42.50.-p Quantum optics
42.70.Qs Photonic bandgap materials
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
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