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Jan 2013

Volume 20, Issue 1, Articles (01xxxx)

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Phys. Plasmas 20, 013108 (2013); http://dx.doi.org/10.1063/1.4775774 (9 pages)

S. A. Yi, V. Khudik, C. Siemon, and G. Shvets
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Derivation of stochastic differential equations for scrape-off layer plasma fluctuations from experimentally measured statistics

A. Mekkaoui

Phys. Plasmas 20, 010701 (2013); http://dx.doi.org/10.1063/1.4789453 (4 pages)

Online Publication Date: 23 January 2013

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A stochastic differential equation for intermittent plasma density dynamics in magnetic fusion edge plasma is derived, which is consistent with the experimentally measured gamma distribution and the theoretically expected quadratic nonlinearity. The plasma density is driven by a multiplicative Wiener process and evolves on the turbulence correlation time scale, while the linear growth is quadratically damped by the fluctuation level. The sensitivity of intermittency to the nonlinear dynamics is investigated by analyzing the nonlinear Langevin representation of the beta process, which leads to a root-square nonlinearity.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.25.Gj Fluctuation and chaos phenomena
52.35.Ra Plasma turbulence
02.50.Ng Distribution theory and Monte Carlo studies
02.30.Hq Ordinary differential equations
02.50.Fz Stochastic analysis
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Plasma turbulence in the scrape-off layer of tokamak devices

Paolo Ricci and B. N. Rogers

Phys. Plasmas 20, 010702 (2013); http://dx.doi.org/10.1063/1.4789551 (4 pages) | Cited 2 times

Online Publication Date: 28 January 2013

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Plasma turbulence is explored in the scrape-off layer of tokamak devices using three-dimensional global two-fluid simulations. Two transport regimes are discussed: one in which the turbulent fluctuations saturate nonlinearly due to the Kelvin-Helmholtz instability, and another in which the fluctuations saturate due to a local flattening of the plasma gradients and associated removal of the linear instability drive. Focusing on the latter regime, analytical estimates of the cross-field transport and plasma profile gradients are obtained that display Bohm-scaling diffusion properties.
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52.55.Fa Tokamaks, spherical tokamaks
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.)
52.35.Ra Plasma turbulence
52.40.Hf Plasma-material interactions; boundary layer effects
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back to top Basic Plasma Phenomena, Waves, Instabilities

A large volume uniform plasma generator for the experiments of electromagnetic wave propagation in plasma

Yang Min (杨敏), Li Xiaoping (李小平), Xie Kai (谢楷), Liu yanming (刘彦明), and Liu Donglin (刘东林)

Phys. Plasmas 20, 012101 (2013); http://dx.doi.org/10.1063/1.4773906 (6 pages)

Online Publication Date: 4 January 2013

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A large volume uniform plasma generator is proposed for the experiments of electromagnetic (EM) wave propagation in plasma, to reproduce a “black out” phenomenon with long duration in an environment of the ordinary laboratory. The plasma generator achieves a controllable approximate uniform plasma in volume of 260 mm× 260 mm× 180 mm without the magnetic confinement. The plasma is produced by the glow discharge, and the special discharge structure is built to bring a steady approximate uniform plasma environment in the electromagnetic wave propagation path without any other barriers. In addition, the electron density and luminosity distributions of plasma under different discharge conditions were diagnosed and experimentally investigated. Both the electron density and the plasma uniformity are directly proportional to the input power and in roughly reverse proportion to the gas pressure in the chamber. Furthermore, the experiments of electromagnetic wave propagation in plasma are conducted in this plasma generator. Blackout phenomena at GPS signal are observed under this system and the measured attenuation curve is of reasonable agreement with the theoretical one, which suggests the effectiveness of the proposed method.
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.75.-d Plasma devices
52.80.Hc Glow; corona
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
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Unique topological characterization of braided magnetic fields

A. R. Yeates and G. Hornig

Phys. Plasmas 20, 012102 (2013); http://dx.doi.org/10.1063/1.4773903 (5 pages)

Online Publication Date: 7 January 2013

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We introduce a topological flux function to quantify the topology of magnetic braids: non-zero, line-tied magnetic fields whose field lines all connect between two boundaries. This scalar function is an ideal invariant defined on a cross-section of the magnetic field, and measures the average poloidal magnetic flux around any given field line, or the average pairwise crossing number between a given field line and all others. Moreover, its integral over the cross-section yields the relative magnetic helicity. Using the fact that the flux function is also an action in the Hamiltonian formulation of the field line equations, we prove that it uniquely characterizes the field line mapping and hence the magnetic topology.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
02.40.Pc General topology

Towards a complete parametrization of the ordinary-mode electromagnetic instability in counterstreaming plasmas. I. Minimizing ion dynamics

D. Ibscher, M. Lazar, M. J. Michno, and R. Schlickeiser

Phys. Plasmas 20, 012103 (2013); http://dx.doi.org/10.1063/1.4774066 (9 pages) | Cited 1 time

Online Publication Date: 7 January 2013

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The ordinary mode instability can be driven by drifting bi-Maxwellian plasma particle distributions with and without temperature anisotropy. Here, the linear instability analysis is generalized for realistic settings, when the plasma streams are magnetized and hot enough. The new parametrization proposed in this study enables a better understanding of the interplay of counterstreaming and temperature anisotropy, providing the derivation of new regimes of the ordinary mode instability. Accurate analytical forms are derived for the instability conditions for general values of the temperature anisotropy, the streaming velocity, and the parallel plasma beta. To keep the analysis straightforward, the role of ions is minimized.
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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.Fi Transport properties
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

A general theory for gauge-free lifting

P. J. Morrison

Phys. Plasmas 20, 012104 (2013); http://dx.doi.org/10.1063/1.4774063 (14 pages) | Cited 3 times

Online Publication Date: 8 January 2013

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A theory for lifting equations of motion for charged particle dynamics, subject to given electromagnetic like forces, up to a gauge-free system of coupled Hamiltonian Vlasov-Maxwell like equations is given. The theory provides very general expressions for the polarization and magnetization vector fields in terms of the particle dynamics description of matter. Thus, as is common in plasma physics, the particle dynamics replaces conventional constitutive relations for matter. Several examples are considered including the usual Vlasov-Maxwell theory, a guiding center kinetic theory, Vlasov-Maxwell theory with the inclusion of spin, and a Vlasov-Maxwell theory with the inclusion of Dirac's magnetic monopoles. All are shown to be Hamiltonian field theories and the Jacobi identity is proven directly.
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52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma

The interaction of two nonplanar solitary waves in electron-positron-ion plasmas: An application in active galactic nuclei

S. K. EL-Labany, E. F. EL-Shamy, R. Sabry, and D. M. Khedr

Phys. Plasmas 20, 012105 (2013); http://dx.doi.org/10.1063/1.4774067 (9 pages)

Online Publication Date: 10 January 2013

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In the present research paper, the effect of bounded nonplanar (cylindrical and spherical) geometry on the interaction between two nonplanar electrostatic solitary waves (NESWs) in electron–positron–ion plasmas has been studied. The extended Poincaré–Lighthill–Kuo method is used to obtain nonplanar phase shifts after the interaction of the two NESWs. This study is a first attempt to investigate nonplanar phase shifts and trajectories for NESWs in a two-fluid plasma (a pair-plasma) consisting of electrons and positrons, as well as immobile background positive ions in nonplanar geometry. The change of phase shifts and trajectories for NESWs due to the effect of cylindrical geometry, spherical geometry, the physical processes (either isothermal or adiabatic), and the positions of two NESWs are discussed. The present investigation may be beneficial to understand the interaction between two NESWs that may occur in active galactic nuclei.
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95.30.Qd Magnetohydrodynamics and plasmas
98.54.Cm Active and peculiar galaxies and related systems (including BL Lacertae objects, blazars, Seyfert galaxies, Markarian galaxies, and active galactic nuclei)
98.62.Js Galactic nuclei (including black holes), circumnuclear matter, and bulges
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Sb Solitons; BGK modes

Spontaneous three-dimensional magnetic reconnection in merging toroidal plasma experiment

Toru Ii and Yasushi Ono

Phys. Plasmas 20, 012106 (2013); http://dx.doi.org/10.1063/1.4774403 (7 pages)

Online Publication Date: 10 January 2013

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We investigated a new phenomenon of three-dimensional (3D) magnetic reconnection in TS-4 torus plasma merging experiments by directly measuring the 3D structures of the current sheet. Removal of all toroidal asymmetry of the device reveals that a strong external drive of reconnection inflow increases the toroidal asymmetry of the current sheet only during the reconnection. This spontaneous 3D deformation of the current sheet increases the reconnection outflow as well as the reconnection electric field, probably because local compression of the current sheet to a thickness less than the ion gyroradius triggers its strong dissipation of the current sheet, responsible for the onset of 3D reconnection. These mechanisms indicate that the 3D reconnection is a newly observed spontaneous process of fast reconnection.
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52.35.Vd Magnetic reconnection
52.55.Fa Tokamaks, spherical tokamaks
52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

A simple class of singular, two species Vlasov equilibria sustaining nonmonotonic potential distributions

L. Nocera and L. J. Palumbo

Phys. Plasmas 20, 012107 (2013); http://dx.doi.org/10.1063/1.4773400 (5 pages)

Online Publication Date: 11 January 2013

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We present new elementary, exact weak singular solutions of the steady state, two species, electrostatic, one dimensional Vlasov-Poisson equations. The distribution of the hot, finite mass, mobile ions is assumed to be log singular at the position of the electric potential's minimum. We show that the electron energy distributions on opposite sides of this minimum are not equal. This leads to a jump discontinuity of the electron distribution across its separatrix. A simple relation exists between the difference of these two electron distributions and that of the ions. The velocity Fourier transform of the electron singular distribution is smooth and appears as a simple Neumann series. Elementary, finite amplitude profiles of the electric potential result from Poisson equation, which are smoothly, but nonmonotonically and asymmetrically distributed in space. Two such profiles are given explicitly as appropriate for a nonmonotonic double layer and for a plasma bounded by a surface. The distributions of both electrons and ions supporting such potential meet smooth and kinetically stable boundary conditions at one plasma boundary. For sufficiently small potential to electron temperature ratios, the nonthermal, discontinuous electron distribution resulting at the other plasma boundary is also stable against Landau damped perturbations of the electron distribution.
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52.25.Fi Transport properties
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.40.Hf Plasma-material interactions; boundary layer effects

Dynamics of exploding plasmas in a large magnetized plasma

C. Niemann, W. Gekelman, C. G. Constantin, E. T. Everson, D. B. Schaeffer, S. E. Clark, D. Winske, A. B. Zylstra, P. Pribyl, S. K. P. Tripathi, D. Larson, S. H. Glenzer, and A. S. Bondarenko

Phys. Plasmas 20, 012108 (2013); http://dx.doi.org/10.1063/1.4773911 (12 pages)

Online Publication Date: 11 January 2013

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The dynamics of an exploding laser-produced plasma in a large ambient magneto-plasma was investigated with magnetic flux probes and Langmuir probes. Debris-ions expanding at super-Alfvénic velocity (up to MA = 1.5) expel the ambient magnetic field, creating a large (>20 cm) diamagnetic cavity. We observe a field compression of up to B/B0 = 1.5 as well as localized electron heating at the edge of the bubble. Two-dimensional hybrid simulations reproduce these measurements well and show that the majority of the ambient ions are energized by the magnetic piston and swept outside the bubble volume. Nonlinear shear-Alfvén waves (δB/B0>25%) are radiated from the cavity with a coupling efficiency of 70% from magnetic energy in the bubble to the wave.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Xz Magnetized plasmas
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.65.Ww Hybrid methods
52.70.Ds Electric and magnetic measurements

Gyrokinetic simulations of reverse shear Alfvén eigenmodes in DIII-D plasmas

Y. Chen, T. Munsat, S. E. Parker, W. W. Heidbrink, M. A. Van Zeeland, B. J. Tobias, and C. W. Domier

Phys. Plasmas 20, 012109 (2013); http://dx.doi.org/10.1063/1.4775776 (11 pages) | Cited 1 time

Online Publication Date: 11 January 2013

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A gyrokinetic ion/mass-less fluid electron hybrid model as implemented in the GEM code [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 837 (2007)] is used to study the reverse shear Alfvén eigenmodes (RSAE) observed in DIII-D, discharge #142111. This is a well diagnosed case with measurement of the core-localized RSAE mode structures and the mode frequency, which can be used to compare with simulations. Simulations reproduce many features of the observation, including the mode frequency up-sweeping in time and the sweeping range. A new algorithmic feature is added to the GEM code for this study. Instead of the gyrokinetic Poisson equation itself, its time derivative, or the vorticity equation, is solved to obtain the electric potential. This permits a numerical scheme that ensures the E × B convection of the equilibrium density profiles of each species cancel each other in the absence of any finite-Larmor-radius effects. These nonlinear simulations generally result in an electron temperature fluctuation level that is comparable to measurements, and a mode frequency spectrum broader than the experimental spectrum. The spectral width from simulations can be reduced if less steep beam density profiles are used, but then the experimental fluctuation level can be reproduced only if a collision rate above the classical level is assumed.
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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.)
52.55.Fa Tokamaks, spherical tokamaks
52.65.Tt Gyrofluid and gyrokinetic simulations
52.25.Gj Fluctuation and chaos phenomena

Nonlinear Raman forward scattering of a short laser pulse in a collisional transversely magnetized plasma

Alireza Paknezhad

Phys. Plasmas 20, 012110 (2013); http://dx.doi.org/10.1063/1.4774390 (9 pages)

Online Publication Date: 15 January 2013

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Nonlinear Raman forward scattering (NRFS) of an intense short laser pulse with a duration shorter than the plasma period through a homogenous collisional transversely magnetized plasma is investigated theoretically when ponderomotive, relativistic and collioninal nonlinearities are taken into account. The plasma is embedded in a uniform magnetic field perpendicular to both, the direction of propagation and electric vector of the radiation field. Nonlinear wave equation is set up and Fourier transformation method is used to solve the coupled equations describing NRFS instability. Finally, the growth rate of this instability is obtained. Thermal effects of plasma electrons and effect of the electron-ion collisions are examined. It is found that the growth rate of Raman forward scattering first decreases on increasing electron thermal velocity, minimizes at an optimum value, and then increases. Our results also show that the growth rate increases by increasing the electron-ion collisions.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
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
52.20.Fs Electron collisions
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.Fi Transport properties

Investigation of an ion-ion hybrid Alfvén wave resonator

S. T. Vincena, W. A. Farmer, J. E. Maggs, and G. J. Morales

Phys. Plasmas 20, 012111 (2013); http://dx.doi.org/10.1063/1.4775777 (12 pages)

Online Publication Date: 16 January 2013

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A theoretical and experimental investigation is made of a wave resonator based on the concept of wave reflection along the confinement magnetic field at a spatial location where the wave frequency matches the local value of the ion-ion hybrid frequency. Such a situation can be realized by shear Alfvén waves in a magnetized plasma with two ion species because this mode has zero parallel group velocity and experiences a cut-off at the ion-ion hybrid frequency. Since the ion-ion hybrid frequency is proportional to the magnetic field, it is expected that a magnetic well configuration in a two-ion plasma can result in an Alfvén wave resonator. Such a concept has been proposed in various space plasma studies and could have relevance to mirror and tokamak fusion devices. This study demonstrates such a resonator in a controlled laboratory experiment using a H+-He+ mixture. The resonator response is investigated by launching monochromatic waves and impulses from a magnetic loop antenna. The observed frequency spectra are found to agree with predictions of a theoretical model of trapped eigenmodes.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
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
52.55.Fa Tokamaks, spherical tokamaks
52.25.Xz Magnetized plasmas

Linear analysis of time dependent properties of Child-Langmuir flow

A. Rokhlenko

Phys. Plasmas 20, 012112 (2013); http://dx.doi.org/10.1063/1.4776690 (11 pages) | Cited 1 time

Online Publication Date: 16 January 2013

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We continue our analysis of the time dependent behavior of the electron flow in the Child-Langmuir system, removing an approximation used earlier. We find a modified set of oscillatory decaying modes with frequencies of the same order as the inverse of the electron transient time. This range (typically MHz) allows simple experimental detection and maybe exploitation. We then study the time evolution of the current in response to a slow change of the anode voltage where the same modes of oscillations appear too. The cathode current in this case is systematically advanced or retarded depending on the direction of the voltage change.
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52.30.-q Plasma dynamics and flow
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.65.Vv Perturbative methods

Small amplitude nonlinear electron acoustic solitary waves in weakly magnetized plasma

Manjistha Dutta, Samiran Ghosh, Rajkumar Roychoudhury, Manoranjan Khan, and Nikhil Chakrabarti

Phys. Plasmas 20, 012113 (2013); http://dx.doi.org/10.1063/1.4776692 (5 pages) | Cited 1 time

Online Publication Date: 16 January 2013

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Nonlinear propagation of electron acoustic waves in homogeneous, dispersive plasma medium with two temperature electron species is studied in presence of externally applied magnetic field. The linear dispersion relation is found to be modified by the externally applied magnetic field. Lagrangian transformation technique is applied to carry out nonlinear analysis. For small amplitude limit, a modified KdV equation is obtained, the modification arising due to presence of magnetic field. For weakly magnetized plasma, the modified KdV equation possesses stable solitary solutions with speed and amplitude increasing temporally. The solutions are valid upto some finite time period beyond which the nonlinear wave tends to wave breaking.
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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
52.25.Xz Magnetized plasmas
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

Linear and nonlinear wave propagation in weakly relativistic quantum plasmas

Martin Stefan and Gert Brodin

Phys. Plasmas 20, 012114 (2013); http://dx.doi.org/10.1063/1.4773897 (6 pages)

Online Publication Date: 17 January 2013

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We consider a recently derived kinetic model for weakly relativistic quantum plasmas. We find that that the effects of spin-orbit interaction and Thomas precession may alter the linear dispersion relation for a magnetized plasma in case of high plasma densities and/or strong magnetic fields. Furthermore, the ponderomotive force induced by an electromagnetic pulse is studied for an unmagnetized plasma. It turns out that for this case the spin-orbit interaction always gives a significant contribution to the quantum part of the ponderomotive force.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.25.Dg Plasma kinetic equations
52.25.Xz Magnetized plasmas
52.27.Ny Relativistic plasmas

Modulational instability of a Langmuir wave in plasmas with energetic tails of superthermal electrons

I. V. Timofeev

Phys. Plasmas 20, 012115 (2013); http://dx.doi.org/10.1063/1.4776683 (7 pages) | Cited 1 time

Online Publication Date: 17 January 2013

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The impact of superthermal electrons on dispersion properties of isotropic plasmas and on the modulational instability of a monochromatic Langmuir wave is studied for the case when the power-law tail of the electron distribution function extends to relativistic velocities and contains most of the plasma kinetic energy. Such an energetic tail of electrons is shown to increase the thermal correction to the Langmuir wave frequency, which is equivalent to the increase of the effective electron temperature in the fluid approach, and has almost no impact on the dispersion of ion-acoustic waves, in which the role of temperature is played by the thermal spread of low-energy core electrons. It is also found that the spectrum of modulational instability in the non-maxwellian plasma narrows significantly, as compared to the equilibrium case, without change of the maximum growth rate and the corresponding wavenumber.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
52.27.Ny Relativistic plasmas

Time-domain simulation of nonlinear radiofrequency phenomena

Thomas G. Jenkins, Travis M. Austin, David N. Smithe, John Loverich, and Ammar H. Hakim

Phys. Plasmas 20, 012116 (2013); http://dx.doi.org/10.1063/1.4776704 (9 pages)

Online Publication Date: 17 January 2013

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Nonlinear effects associated with the physics of radiofrequency wave propagation through a plasma are investigated numerically in the time domain, using both fluid and particle-in-cell (PIC) methods. We find favorable comparisons between parametric decay instability scenarios observed on the Alcator C-MOD experiment [J. C. Rost, M. Porkolab, and R. L. Boivin, Phys. Plasmas 9, 1262 (2002)] and PIC models. The capability of fluid models to capture important nonlinear effects characteristic of wave-plasma interaction (frequency doubling, cyclotron resonant absorption) is also demonstrated.
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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.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.55.Fa Tokamaks, spherical tokamaks
52.65.Rr Particle-in-cell method
02.60.-x Numerical approximation and analysis

Electromagnetic waves destabilized by runaway electrons in near-critical electric fields

A. Kómár, G. I. Pokol, and T. Fülöp

Phys. Plasmas 20, 012117 (2013); http://dx.doi.org/10.1063/1.4776666 (12 pages)

Online Publication Date: 18 January 2013

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Runaway electron distributions are strongly anisotropic in velocity space. This anisotropy is a source of free energy that may destabilize electromagnetic waves through a resonant interaction between the waves and the energetic electrons. In this work, we investigate the high-frequency electromagnetic waves that are destabilized by runaway electron beams when the electric field is close to the critical field for runaway acceleration. Using a runaway electron distribution appropriate for the near-critical case, we calculate the linear instability growth rate of these waves and conclude that the obliquely propagating whistler waves are most unstable. We show that the frequencies, wave numbers, and propagation angles of the most unstable waves depend strongly on the magnetic field. Taking into account collisional and convective damping of the waves, we determine the number density of runaways that is required to destabilize the waves and show its parametric dependences.
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.20.Fs Electron collisions
52.25.Fi Transport properties
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

The incomplete plasma dispersion function: Properties and application to waves in bounded plasmas

S. D. Baalrud

Phys. Plasmas 20, 012118 (2013); http://dx.doi.org/10.1063/1.4789387 (13 pages)

Online Publication Date: 25 January 2013

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The incomplete plasma dispersion function is a generalization of the plasma dispersion function in which the defining integral spans a semi-infinite, rather than infinite, domain. It is useful for describing the linear dielectric response and wave dispersion in non-Maxwellian plasmas when the distribution functions can be approximated as Maxwellian over finite, or semi-infinite, intervals in velocity phase-space. A ubiquitous example is the depleted Maxwellian electron distribution found near boundary sheaths or double layers, where the passing interval can be modeled as Maxwellian with a lower temperature than the trapped interval. The depleted Maxwellian is used as an example to demonstrate the utility of using the incomplete plasma dispersion function for calculating modifications to wave dispersion relations.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.40.Kh Plasma sheaths
52.25.Mq Dielectric properties

Pressure driven tearing and interchange modes in the reversed field pinch

R. Paccagnella

Phys. Plasmas 20, 012119 (2013); http://dx.doi.org/10.1063/1.4789446 (6 pages)

Online Publication Date: 28 January 2013

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In this work, the magneto-hydro-dynamic stability of pressure driven modes in the reversed field pinch has been analyzed. It is shown that at low and intermediate β's, i.e., typically for values below 20-25%, the tearing parity is dominant, while only at very high β, well above the achieved experimental values, at least part of the modes are converted to ideal interchange instabilities. Before their transition to ideal instabilities, according to their Lundquist number scaling, they can be classified as resistive-g modes.
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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
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.58.Lq Z-pinches, plasma focus, and other pinch devices

Competition of circularly polarized laser modes in the modulation instability of hot magnetoplasma

N. Sepehri Javan

Phys. Plasmas 20, 012120 (2013); http://dx.doi.org/10.1063/1.4789452 (6 pages) | Cited 1 time

Online Publication Date: 28 January 2013

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The present study is aimed to investigate the problem of modulation instability of an intense laser beam in the hot magnetized plasma. The propagation of intense circularly polarized laser beam along the external magnetic field is considered using a relativistic fluid model. The nonlinear equation describing the interaction of laser pulse with magnetized hot plasma is derived in the quasi-neutral approximation, which is valid for hot plasma. Nonlinear dispersion equation for hot plasma is obtained. For left- and right-hand polarizations, the growth rate of instability is achieved and the effect of temperature, external magnetic field, and kind of polarization on the growth rate is considered. It is observed that for the right-hand polarization, increase of magnetic field leads to the increasing of growth rate. Also for the left-hand polarization, increase of magnetic field inversely causes decrease of the growth rate.
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52.38.-r Laser-plasma interactions
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
42.65.-k Nonlinear optics

Ion pseudoheating by low-frequency Alfvén waves revisited

Chuanfei Dong and Nagendra Singh

Phys. Plasmas 20, 012121 (2013); http://dx.doi.org/10.1063/1.4789608 (10 pages)

Online Publication Date: 29 January 2013

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Pseudoheating of ions in the presence of Alfvén waves is studied. We show that this process can be explained by E × B drift, indicating that the pseudoheating is a consequence of equilibrium MHD system. The analytic solution obtained in this paper is quantitatively in accordance with previous results. Our simulation results show that the Maxwellian distribution is broadened during the pseudoheating; however, the shape of the broadening distribution function depends on the number of wave modes (i.e., a wave spectrum or a monochromatic dispersionless wave) and the initial thermal speed of ions (vp). It is of particular interests to find that the Maxwellian shape is more likely to maintain during the pseudoheating under a wave spectrum compared with a monochromatic wave. It significantly improves our understanding of heating processes in interplanetary space where Alfvénic turbulences exist pervasively. Compared with a monochromatic Alfvén wave, E × B drift produces more energetic particles in a broad spectrum of Alfvén waves, especially when the Alfvénic turbulence with phase coherent wave modes is given. Such particles may escape from the region of interaction with the Alfvén waves and can contribute to fast particle population in astrophysical and space plasmas.
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52.50.Gj Plasma heating by particle beams
52.25.Fi Transport properties
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.35.Ra Plasma turbulence
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Non-planar ion-acoustic solitary waves and their head-on collision in a plasma with nonthermal electrons and warm adiabatic ions

Jiu-Ning Han, Yong-Lin He, Yan Chen, Ke-Zhi Zhang, and Bao-Hong Ma

Phys. Plasmas 20, 012122 (2013); http://dx.doi.org/10.1063/1.4789749 (8 pages) | Cited 1 time

Online Publication Date: 29 January 2013

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By using the model of Cairns et al. [Geophys. Rev. Lett. 22, 2709 (1995)], the head-on collision of cylindrical/spherical ion-acoustic solitary waves in an unmagnetized non-planar plasma consisting of warm adiabatic ions and nonthermally distributed electrons is investigated. The extended Poincaré-Lighthill-Kuo perturbation method is used to derive the modified Korteweg-de Vries equations for ion-acoustic solitary waves in this plasma system. The effects of the plasma geometry m, the ion to electron temperature ratio σ, and the nonthermality of the electron distribution α on the interaction of the colliding solitary waves are studied. It is found that the plasma geometries have a big impact on the phase shifts of solitary waves. Also it is important to note that the phase shifts induced by the collision of compressive and rarefactive solitary waves are very different. We point out that this study is useful to the investigations about the observations of electrostatic solitary structures in astrophysical as well as in experimental plasmas with nonthermal energetic electrons.
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52.35.Sb Solitons; BGK modes
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
02.30.Jr Partial differential equations
52.65.Vv Perturbative methods
52.25.-b Plasma properties

Experimental observation of left polarized wave absorption near electron cyclotron resonance frequency in helicon antenna produced plasma

Kshitish K. Barada, P. K. Chattopadhyay, J. Ghosh, Sunil Kumar, and Y. C. Saxena

Phys. Plasmas 20, 012123 (2013); http://dx.doi.org/10.1063/1.4789456 (6 pages)

Online Publication Date: 31 January 2013

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Asymmetry in density peaks on either side of an m = +1 half helical antenna is observed both in terms of peak position and its magnitude with respect to magnetic field variation in a linear helicon plasma device [Barada et al., Rev. Sci. Instrum. 83, 063501 (2012)]. The plasma is produced by powering the m = +1 half helical antenna with a 2.5 kW, 13.56 MHz radio frequency source. During low magnetic field (B < 100 G) operation, plasma density peaks are observed at critical magnetic fields on either side of the antenna. However, the density peaks occurred at different critical magnetic fields on both sides of antenna. Depending upon the direction of the magnetic field, in the m = +1 propagation side, the main density peak has been observed around 30 G of magnetic field. On this side, the density peak around 5 G corresponding to electron cyclotron resonance (ECR) is not very pronounced, whereas in the m = −1 propagation side, very pronounced ECR peak has been observed around 5 G. Another prominent density peak around 12 G has also been observed in m = −1 side. However, no peak has been observed around 30 G on this m = −1 side. This asymmetry in the results on both sides is explained on the basis of polarization reversal of left hand polarized waves to right hand polarized waves and vice versa in a bounded plasma system. The density peaking phenomena are likely to be caused by obliquely propagating helicon waves at the resonance cone boundary.
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52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
52.75.-d Plasma devices
52.25.-b Plasma properties
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