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Jan 2008

Volume 15, Issue 1, Articles (01xxxx)

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Phys. Plasmas 15, 013109 (2008); http://dx.doi.org/10.1063/1.2825663 (15 pages)

L. Yin, B. J. Albright, K. J. Bowers, W. Daughton, and H. A. Rose
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back to top Basic Plasma Phenomena, Waves, Instabilities

Neutrino induced charge in a superdense two-electron Fermi plasma

L. A. Rios and P. K. Shukla

Phys. Plasmas 15, 012101 (2008); http://dx.doi.org/10.1063/1.2826438 (5 pages) | Cited 5 times

Online Publication Date: 2 January 2008

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Using plasma physics methods, the effective neutrino charge in a superdense two-electron Fermi plasma is determined. The Fermi plasma has distinct groups of hot and cold electrons. Accounting for the quantum statistical pressure for the hot electron component and the quantum force associated with the quantum Bohm potential, the neutrino induced charge produced by the neutrino driving force is estimated. The influence of the quantum-mechanical effects on the neutrino effective electric charge has been investigated.
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52.40.-w Plasma interactions (nonlaser)

Growth of resistive instabilities in E×B plasma discharge simulations

E. Fernandez, M. K. Scharfe, C. A. Thomas, N. Gascon, and M. A. Cappelli

Phys. Plasmas 15, 012102 (2008); http://dx.doi.org/10.1063/1.2823033 (10 pages) | Cited 7 times

Online Publication Date: 8 January 2008

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Two-dimensional hybrid numerical simulations of E×B discharges used in Hall thruster propulsion point to the presence of strong fluctuations attributable to resistive instabilities in the frequency range of f ≈ 0.1–10 MHz and the wavenumber range of λ−1 ≈ 10–500 m−1. Analytical analyses confirm that these resistive modes are of the convective type, become increasingly unstable at low electron mobility, and are particularly intense at high voltage. The simulations, which model cross-field electron flow via an experimentally measured mobility, exhibit large fluctuation power in a region corresponding to a strong electron transport barrier. The analysis gives an electron mobility (μe) -dependent growth rate (γ) scaling as γ ∼ μe−1/2. The predicted phase velocity of these waves is close to the ion velocity, somewhat lower than that seen in the simulations. Including the electron pressure contribution lowers the growth rate at high frequencies, and introduces a phase velocity that is shifted by ± the ion acoustic speed for the stable and unstable branch, respectively. Surprisingly, the phase velocity of the strong disturbances at high frequency seen in the simulations is found to be in agreement with that of the initially stable branch. Finite ionization/particle wall recombination does not change the overall conclusions at high frequencies. However, at lower f or larger λ, the growth rate of the instability is dominated by the ionization rate, and the disturbances are better described as “ionization” instabilities. The transition/competition between ionization, electron pressure, and resistive behavior gives rise to a “quiescent frequency band” where the growth rate is found to be small, consistent with what is seen in the numerical experiments. While simple linear analysis captures much of the observed simulation behavior, comparison with limited experimental data at low frequency suggests that other effects, in particular azimuthal dynamics, are very important, and further motivate extending the hybrid simulation models to three dimensions.
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52.80.-s Electric discharges
52.65.-y Plasma simulation
52.25.Fi Transport properties

Spectral gap of shear Alfvén waves in a periodic array of magnetic mirrors

Yang Zhang, W. W. Heidbrink, H. Boehmer, R. McWilliams, Guangye Chen, B. N. Breizman, S. Vincena, T. Carter, D. Leneman, W. Gekelman, P. Pribyl, and B. Brugman

Phys. Plasmas 15, 012103 (2008); http://dx.doi.org/10.1063/1.2827518 (14 pages) | Cited 12 times

Online Publication Date: 8 January 2008

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A multiple magnetic mirror array is formed at the Large Plasma Device (LAPD) [ W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 (1991) ] to study axial periodicity-influenced Alfvén spectra. Shear Alfvén waves (SAW) are launched by antennas inserted in the LAPD plasma and diagnosed by B-dot probes at many axial locations. Alfvén wave spectral gaps and continua are formed similar to wave propagation in other periodic media due to the Bragg effect. The measured width of the propagation gap increases with the modulation amplitude as predicted by the solutions to Mathieu’s equation. A two-dimensional finite-difference code modeling SAW in a mirror array configuration shows similar spectral features. Machine end-reflection conditions and damping mechanisms including electron-ion Coulomb collision and electron Landau damping are important for simulation.
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28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium
52.70.-m Plasma diagnostic techniques and instrumentation
52.75.-d Plasma devices

Ions motion effects on the full unstable spectrum in relativistic electron beam plasma interaction

A. Bret and M. E. Dieckmann

Phys. Plasmas 15, 012104 (2008); http://dx.doi.org/10.1063/1.2828607 (13 pages) | Cited 7 times

Online Publication Date: 9 January 2008

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A relativistic fluid model is implemented to assess the role of the ions motion in the linear phase of relativistic beam plasma electromagnetic instabilities. The all unstable wave vector spectrum is investigated, allowing us to assess how ion motions modify the competition between every possible instability. Beam densities up to the plasma one are considered. Due to the fluid approach, the temperatures must remain small, i.e., nonrelativistic. In the cold limit, ions motion affect the most unstable mode when the beam gamma factor γb≳αM/mZi, α being the beam to plasma density ratio, Zi the ion charge, M their mass, and m the electrons. The return current plays an important role by prompting Buneman-type instabilities which remain in the nonrelativistic regime up to high beam densities. Nonrelativistic temperatures only slightly affect these conclusions, except in the diluted beam regime where they can stabilize the Buneman modes.
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52.40.Mj Particle beam interactions in plasmas
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.25.Jm Ionization of plasmas
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.27.Ny Relativistic plasmas

Drift mode in a bounded plasma having two-ion species

Ali Ahmad, M. Sajid, and H. Saleem

Phys. Plasmas 15, 012105 (2008); http://dx.doi.org/10.1063/1.2826440 (6 pages) | Cited 3 times

Online Publication Date: 10 January 2008

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The drift wave is investigated in a two-ion species plasma in several different cases. The global drift mode is studied in a plasma bounded in a cylinder having Gaussian density profile corresponding to different poloidal wavenumbers. The frequency of the mode becomes a little larger when it is investigated without including the ion cyclotron wave dynamics. The effect of magnetic shear on the wave propagation along the density gradient is studied in a Cartesian geometry assuming absorbing boundary. It is found that the wave amplitude is reduced when two-ion species are present (with the same concentration) compared to pure electron-ion plasma.
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52.25.-b Plasma properties
52.35.Kt Drift waves
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, field structure, etc.
52.27.Cm Multicomponent and negative-ion plasmas

Creation of finely focused particle beams from single-component plasmas

T. R. Weber, J. R. Danielson, and C. M. Surko

Phys. Plasmas 15, 012106 (2008); http://dx.doi.org/10.1063/1.2817967 (10 pages) | Cited 5 times

Online Publication Date: 16 January 2008

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In a recent communication [ Danielson et al., Appl. Phys. Lett. 90, 081503 (2007) ], a nondestructive technique was described to create finely focused beams of electron-mass, charged particles (i.e., electrons or positrons) from single-component plasmas confined in a Penning–Malmberg trap. This paper amplifies and expands upon those results, providing a more complete study of this method of beam formation. A simple model for beam extraction is presented, and an expression for a Gaussian beam profile is derived when the number of extracted beam particles is small. This expression gives a minimum beam diameter of four Debye lengths (full width to 1/e) and is verified using electron plasmas over a broad range of plasma temperatures and densities. Numerical procedures are outlined to predict the profiles of beams with large numbers of extracted particles. Measured profiles of large beams are found in fair agreement with these predictions. The extraction of over 50% of a trapped plasma into a train of nearly identical beams is demonstrated. Applications and extensions of this technique to create state-of-the-art positron beams are discussed.
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52.27.Jt Nonneutral plasmas
41.75.Fr Electron and positron beams
07.77.Ka Charged-particle beam sources and detectors

Self-gravitational instability of rotating anisotropic heat-conducting plasma

R. P. Prajapati, A. K. Parihar, and R. K. Chhajlani

Phys. Plasmas 15, 012107 (2008); http://dx.doi.org/10.1063/1.2828074 (8 pages) | Cited 4 times

Online Publication Date: 18 January 2008

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The self-gravitational instability of rotating anisotropic heat-conducting plasma with modified Chew–Goldberger–Low equations is investigated. The general dispersion relation is obtained using normal mode analysis by constructing the linearized set of equations. This dispersion relation is further reduced for propagation parallel and perpendicular to the direction of magnetic field. These conditions are discussed for axis of rotation along and perpendicular to the magnetic field. It is found that the heat flux vector does not influence the transverse mode of propagation for both cases of rotation and Jeans condition remains unchanged. In case of propagation parallel to the magnetic field with axis of rotation perpendicular to the magnetic field, we get the dispersion relation, which shows the joint effect of rotation and heat flux vector. The two separate modes of propagation are obtained in terms of rotation and heat flux vector for rotation parallel to the magnetic field. It is demonstrated that the Alfvén wave and the associated firehose instability are not affected by the presence of heat flux corrections and rotation also. The numerical analysis is performed to show the effect of rotation, pressure anisotropy, and heat flux parameter on the condition of instability in the spiral arms of galaxy. The Jeans condition of gravitational instability is obtained for both the cases of propagation.
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95.30.Qd Magnetohydrodynamics and plasmas
98.58.-w Interstellar medium (ISM) and nebulae in external galaxies
98.62.-g Characteristics and properties of external galaxies and extragalactic objects

Nonlinear filamentation of a current-carrying plasma

A. R. Niknam and B. Shokri

Phys. Plasmas 15, 012108 (2008); http://dx.doi.org/10.1063/1.2833595 (4 pages) | Cited 7 times

Online Publication Date: 22 January 2008

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The nonlinear filamentation in a nonrelativistic collisional current-carrying plasma in the diffusion frequency region is investigated. It is shown that by using the two-fluid plasma equations and Ampere’s law and assuming that the plasma is nonisothermal and inhomogeneous, the spatial evolution of the magnetic field in a plasma is described by the Lienard nonlinear differential equation. Also, it is shown that a transverse filamentation and density steepening can occur in the static limit. Furthermore, the profiles of magnetic field and the electron density variation have a nonsinusoidal shape in the nonlinear regime. Moreover it is shown that the shape of the transverse filamentation varies due to the nonlinear effect in the static limit.
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52.25.Fi Transport properties
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.)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)

Debye-shielding potential in the presence of pair correlations

Anirban Bose and M. S. Janaki

Phys. Plasmas 15, 012109 (2008); http://dx.doi.org/10.1063/1.2832682 (5 pages)

Online Publication Date: 24 January 2008

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The first-order kinetic equation of the Bogoliubov–Born–Green–Kirkwood–Yvon hierarchy of equations for an equilibrium inhomogeneous plasma is shown to contain an effective force resulting from pair correlations that depends on the gradient of the average electric field modulus. Such a kinetic equation is utilized to obtain a Boltzmann distribution that includes the effects of correlations. For an electron-ion plasma with stationary ions and finite electron-electron correlations, the nature of the Debye-screening potential is investigated.
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52.25.Dg Plasma kinetic equations
05.20.-y Classical statistical mechanics

Quantum effects on Rayleigh–Taylor instability in magnetized plasma

Jintao Cao, Haijun Ren, Zhengwei Wu, and Paul K. Chu

Phys. Plasmas 15, 012110 (2008); http://dx.doi.org/10.1063/1.2833588 (6 pages) | Cited 10 times

Online Publication Date: 24 January 2008

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The effects of the quantum mechanism and magnetic field on Rayleigh–Taylor (RT) instability in an ideal incompressible plasma are investigated. The explicit expression of the linear growth rate is obtained in the presence of fixed boundary conditions. It is shown that the magnetic field has a stabilizing effect on RT instability similar to the behavior in classical plasmas and RT instability is affected significantly by quantum effects. Quantum effects are also shown to suppress RT instability with the appropriate physical quantities. Some astrophysical parameters are discussed as an example to investigate the new effects.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

The instabilities induced by electrostatic fields and gradients in a plasma shock front

Yong He, Xiwei Hu, Zhonghe Jiang, and Jianhong Lü

Phys. Plasmas 15, 012111 (2008); http://dx.doi.org/10.1063/1.2834726 (4 pages) | Cited 2 times

Online Publication Date: 29 January 2008

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The linear instabilities induced by the electrostatic fields and gradients of equilibrium parameters in a plasma shock front are analyzed for the plasma shock structure. Small perturbations as well as the steady-state shock structure are described by a set of coupled two-fluid and Poisson equations. The dispersion relations are obtained at high frequency in two cases, in which the wave vectors are, respectively, parallel and perpendicular to the shock propagation direction. The imaginary parts of the frequency (growth rates) of the instabilities are dependent on the fields and the gradients.
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52.35.Tc Shock waves and discontinuities
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

On the magnetohydrodynamic load and the magnetohydrodynamic metage

Sagar Chakraborty and Partha Guha

Phys. Plasmas 15, 012112 (2008); http://dx.doi.org/10.1063/1.2836617 (7 pages)

Online Publication Date: 30 January 2008

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In analogy with the load and the metage in hydrodynamics, this paper defines magnetohydrodynamic load and magnetohydrodynamic metage in the case of magnetofluids. They can be used to write the magnetic field in MHD in Clebsch’s form. It has been shown herein how these two concepts can be utilized to derive the magnetic analog of the Ertel’s theorem and also, how in the presence of nontrivial topology of the magnetic field in the magnetofluid one may associate the linking number of the magnetic field lines with the invariant MHD loads. The paper illustrates that the symmetry translation of the MHD metage in the corresponding label space generates the conservation of cross helicity.
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47.65.Cb Magnetic fluids and ferrofluids
75.50.Mm Magnetic liquids

Nonresonant power transfer in plasma-surface interactions via two-surface wave decay

Yu. A. Akimov and K. Ostrikov

Phys. Plasmas 15, 012113 (2008); http://dx.doi.org/10.1063/1.2836621 (7 pages)

Online Publication Date: 31 January 2008

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The excitation of pairs of electron surface waves via nonresonant decay of plasma waves incident onto a solid surface is studied in the context of controlling the interaction of pulsed electromagnetic radiation with plasma-exposed solid surfaces. The role of the plasma-exposed surfaces in nonlinear heating of the plasma edge and related power transfer is discussed. It is shown that the maximum efficiency of the power transfer at solid surfaces with dielectric permittivity εd<3 corresponds to the resonant two-surface wave decay. On the other hand, for solids with εd>3 the maximum power transfer efficiency is achieved through nonresonant excitation of the quasistatic surface waves. In this case the plasma waves generated by external radiation dissipate their energy into the plasma periphery most effectively.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.50.-b Plasma production and heating
back to top Nonlinear Phenomena, Turbulence, Transport

A model for two-dimensional bursty turbulence in magnetized plasmas

Sergio Servidio, Leonardo Primavera, Vincenzo Carbone, Alain Noullez, and Kristoffer Rypdal

Phys. Plasmas 15, 012301 (2008); http://dx.doi.org/10.1063/1.2825656 (10 pages) | Cited 4 times

Online Publication Date: 2 January 2008

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The nonlinear dynamics of two-dimensional electrostatic interchange modes in a magnetized plasma is investigated through a simple model that replaces the instability mechanism due to magnetic field curvature by an external source of vorticity and mass. Simulations in a cylindrical domain, with a spatially localized and randomized source at the center of the domain, reveal the eruption of mushroom-shaped bursts that propagate radially and are absorbed by the boundaries. Burst sizes and the interburst waiting times exhibit power-law statistics, which indicates long-range interburst correlations, similar to what has been found in sandpile models for avalanching systems. It is shown from the simulations that the dynamics can be characterized by a Yaglom relation for the third-order mixed moment involving the particle number density as a passive scalar and the E×B drift velocity, and hence that the burst phenomenology can be described within the framework of turbulence theory. Statistical features are qualitatively in agreement with experiments of intermittent transport at the edge of plasma devices, and suggest that essential features such as transport can be described by this simple model of bursty turbulence.
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52.20.-j Elementary processes in plasmas
05.45.-a Nonlinear dynamics and chaos
52.65.Pp Monte Carlo methods

Three-dimensional simulations of compressible tearing instability

Simone Landi, Pasquale Londrillo, Marco Velli, and Lapo Bettarini

Phys. Plasmas 15, 012302 (2008); http://dx.doi.org/10.1063/1.2825006 (15 pages) | Cited 4 times

Online Publication Date: 2 January 2008

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Three-dimensional numerical simulations of the tearing instability in the framework of compressible and resistive magnetohydrodynamics are presented. Simulations have been performed with a novel Eulerian conservative high order code, including an explicit resistivity, which uses implicit high order numerical schemes having higher spectral resolution than classical schemes. The linear and non linear evolution of the tearing instability has been followed for force-free and pressure-balanced initial equilibrium configurations. Pressure equilibrium configurations are subject to a secondary instability which drives the system toward a quasi two dimensional structure oriented perpendicularly to the initial configuration. The development of secondary instabilities is suppressed by a guide field allowing the coalescence instability to fully develop in the system. Force-free initial configurations follow an intermediate path with respect the previous cases: Strong coalescence of magnetic islands, due to the non linear evolution of the tearing instability, is observed before the system enters in a phase dominated by 3D modes. The histories of the differing initial current-sheet equilibria have counterparts in the energy spectra that, for all three cases, are observed to be strongly anisotropic.
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52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.65.Kj Magnetohydrodynamic and fluid equation
52.65.-y Plasma simulation

Transport of parallel momentum by collisionless drift wave turbulence

P. H. Diamond, C. J. McDevitt, Ö. D. Gürcan, T. S. Hahm, and V. Naulin

Phys. Plasmas 15, 012303 (2008); http://dx.doi.org/10.1063/1.2826436 (21 pages) | Cited 53 times

Online Publication Date: 8 January 2008

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This paper presents a novel, unified approach to the theory of turbulent transport of parallel momentum by collisionless drift waves. The physics of resonant and nonresonant off-diagonal contributions to the momentum flux is emphasized, and collisionless momentum exchange between waves and particles is accounted for. Two related momentum conservation theorems are derived. These relate the resonant particle momentum flux, the wave momentum flux, and the refractive force. A perturbative calculation, in the spirit of Chapman–Enskog theory, is used to obtain the wave momentum flux, which contributes significantly to the residual stress. A general equation for mean k∥ (〈k∥〉) is derived and used to develop a generalized theory of symmetry breaking. The resonant particle momentum flux is calculated, and pinch and residual stress effects are identified. The implications of the theory for intrinsic rotation and momentum transport bifurcations are discussed.
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52.35.Kt Drift waves
52.35.Ra Plasma turbulence

Improved model for transport driven by drift modes in tokamaks

Federico D. Halpern, Annika Eriksson, Glenn Bateman, Arnold H. Kritz, Alexei Pankin, Christopher M. Wolfe, and Jan Weiland

Phys. Plasmas 15, 012304 (2008); http://dx.doi.org/10.1063/1.2829762 (11 pages) | Cited 9 times

Online Publication Date: 16 January 2008

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A comparison is made between two versions of the Weiland model for computing anomalous transport driven by drift modes such as the ion temperature gradient (ITG) and trapped electron mode (TEM) in tokamak plasmas. Both are quasilinear fluid models that include physical effects resulting from finite β, magnetic shear, electron-ion collisions, impurities, and fast ions. An outline of the derivation is presented for the newer Weiland19 model, which includes a more accurate description of the effects of finite β, low and negative magnetic shear, plasma elongation, varying correlation lengths, particle pinch, and momentum transport. It is shown that the two models produce nearly the same ion thermal diffusivity as a function of normalized temperature gradient in a circular plasma with moderate magnetic shear, low β, and moderately low density gradient. The models differ significantly at low magnetic shear and in elongated plasmas with high β. In addition, the two models differ significantly in the behavior of the transition between moderate transport driven by ITG/TEM modes at low β and large transport driven by magnetohydrodynamic instabilities at high β. In the older Weiland14 model, the transition occurs at a low value of β that is insensitive to plasma elongation and magnetic shear. In the newer Weiland19 model, the transition occurs at a relatively large value of β that is a sensitive function of plasma elongation and magnetic shear.
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52.35.Kt Drift waves
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
94.20.Fg Plasma temperature and density
52.25.Fi Transport properties
52.55.Fa Tokamaks, spherical tokamaks

Intermittency in the heat and particle transports in the SINP tokamak scrape-off layer

S. K. Saha and S. Chowdhury

Phys. Plasmas 15, 012305 (2008); http://dx.doi.org/10.1063/1.2828479 (7 pages) | Cited 1 time

Online Publication Date: 22 January 2008

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The intermittent heat and particle transports have been studied in the scrape-off layer of the SINP tokamak. Properties of the plasma structures, responsible for the intermittency, have been measured by the conditional averaging technique. The probability distribution functions of the fluctuations, including temperature fluctuations, obey non-Gaussian statistics. Wavelet analysis has shown that the cross-correlation between two probes is also intermittent in time and is connected to the passage of plasma structures. The structures decay in density as they move radially outward but their temperature is found to decay more rapidly.
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52.55.Fa Tokamaks, spherical tokamaks
52.25.Gj Fluctuation and chaos phenomena
52.25.Fi Transport properties

Theory and simulations of principle of minimum dissipation rate

Dastgeer Shaikh, B. Dasgupta, G. P. Zank, and Q. Hu

Phys. Plasmas 15, 012306 (2008); http://dx.doi.org/10.1063/1.2828539 (5 pages) | Cited 5 times

Online Publication Date: 22 January 2008

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We perform a self-consistent, time-dependent numerical simulations of dissipative turbulent plasmas at a higher Lundquist number, typically up to O(106), using full three-dimensional compressible magnetohydrodynamics code with a numerical resolution of 1283. Our simulations follow the time variation of global helicity, magnetic energy, and the dissipation rate and show that the global helicity remains approximately constant, while magnetic energy is decaying faster and the dissipation rate is decaying even faster than the magnetic energy. This establishes that the principle of minimum dissipation rate under the constraint of (approximate) conservation of global helicity is a viable approach for plasma relaxation.
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52.35.Ra Plasma turbulence
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.65.Kj Magnetohydrodynamic and fluid equation

Three-dimensional global fluid simulations of cylindrical magnetized plasmas

V. Naulin, T. Windisch, and O. Grulke

Phys. Plasmas 15, 012307 (2008); http://dx.doi.org/10.1063/1.2829603 (11 pages) | Cited 17 times

Online Publication Date: 23 January 2008

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Plasma dynamics in cylindrical geometry, with many well diagnosed experiments in operation worldwide, is of fundamental interest. These linear machines can provide an unique testing ground for direct and detailed comparisons of numerical simulations of nonlinear plasma dynamics with experiments. Thus, it is possible to assess the reproductive and predictive capabilities of plasma simulations in unprecedented detail. Here, three-dimensional global fluid simulations of a cylindrical magnetized plasma are presented. This plasma is characterized by the existence of spatially localized sources and sinks. The traditional scale separation paradigm is not applied in the simulation model to account for the important evolution of the background profiles due to the dynamics of turbulent fluctuations. Furthermore, the fluid modeling of sheath boundary conditions, which determine the plasma conditions, are an important ingredient to the code presented here. The linear properties of the model equations are studied and are shown to agree well with experimental observations of linear drift modes. The fully nonlinear simulations are characterized by turbulent fluctuations, which are dominated by low mode numbers in the large radial pressure gradient region. In the far plasma edge, the fluctuations display an intermittent character due to convection within radially extended spatiotemporal potential fluctuations. This paper reports on the model and general code results, while the detailed comparison to a specific experiment is left to a follow-up paper.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.30.Ex Two-fluid and multi-fluid plasmas
52.65.Kj Magnetohydrodynamic and fluid equation
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Ra Plasma turbulence

Regimes of the interactions of high-intensity plane electromagnetic waves with electron-ion plasmas

O. B. Shiryaev

Phys. Plasmas 15, 012308 (2008); http://dx.doi.org/10.1063/1.2832699 (10 pages) | Cited 6 times

Online Publication Date: 29 January 2008

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A set of fully nonlinear equations is derived from the Maxwell equations and the electron and ion fluid dynamics in one-dimensional geometry as a model of the interactions of extremely intense plane electromagnetic waves with cold locally non-neutral electron-ion plasmas. The problem is solved for phase velocities close to the speed of light numerically and with the help of asymptotic techniques. Depending on the field magnitudes, three nonlinear regimes are found to occur in the system. At plane-wave intensities inducing relativistic electron fluid dynamics but insufficient to cause significant ion motions, the model reverts to the classic Akhiezer–Polovin problem and yields its solutions describing the nonlinear self-modulation of the electromagnetic fields in plasmas. The types of regimes sustained at field strengths entailing substantial ion dynamics are the self-modulation with a splitting of the plane-wave field spectrum into a set of closely spaced bands, and the harmonics generation with a spectrum comprising broadly distanced bands. The latter two regimes correspond to a subcritical and an overcritical range of the plasma longitudinal field potentials.
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52.35.-g Waves, oscillations, and instabilities in plasmas and intense beams
04.30.Nk Wave propagation and interactions
42.65.-k Nonlinear optics
11.80.-m Relativistic scattering theory
96.50.Tf MHD waves; plasma waves, turbulence
back to top Magnetically Confined Plasmas, Heating, Confinement

Extension and comparison of neoclassical models for poloidal rotation in tokamaks

W. M. Stacey

Phys. Plasmas 15, 012501 (2008); http://dx.doi.org/10.1063/1.2829073 (7 pages) | Cited 13 times

Online Publication Date: 18 January 2008

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Several neoclassical models for the calculation of poloidal rotation in tokamaks were rederived within a common framework, extended to include additional physics and numerically compared. The importance of new physics phenomena not usually included in poloidal rotation calculations (e.g., poloidal electric field, V×B force resulting from enhanced radial particle flow arising from the ionization of recycling neutrals) was examined. Extensions of the Hirshman–Sigmar, Kim–Diamond–Groebner, and Stacey–Sigmar poloidal rotation models are presented.
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52.55.Fa Tokamaks, spherical tokamaks

Drift-tearing magnetic islands in tokamak plasmas

R. Fitzpatrick and F. L. Waelbroeck

Phys. Plasmas 15, 012502 (2008); http://dx.doi.org/10.1063/1.2829757 (15 pages) | Cited 7 times

Online Publication Date: 23 January 2008

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A systematic fluid theory of nonlinear magnetic island dynamics in conventional low-β, large aspect-ratio, circular cross-section tokamak plasmas is developed using an extended magnetohydrodynamics model that incorporates diamagnetic flows, ion gyroviscosity, fast parallel electron heat transport, the ion sound wave, the drift wave, and average magnetic field-line curvature. The model excludes the compressible Alfvén wave, geodesic field-line curvature, neoclassical effects, and ion Landau damping. A collisional closure is used for plasma dynamics parallel to the magnetic field. Two distinct branches of island solutions are found, namely the “sonic” and “hypersonic” branches. Both branches are investigated analytically, using suitable ordering schemes, and in each case the problem is reduced to a relatively simple set of nonlinear differential equations that can be solved numerically via iteration. The solution determines the island phase velocity, relative to the plasma, and the effect of local currents on the island stability. Sonic islands are relatively wide, flatten both the temperature and density profiles, and tend to propagate close to the local ion fluid velocity. Hypersonic islands, on the other hand, are relatively narrow, only flatten the temperature profile, radiate drift-acoustic waves, and tend to propagate close to the local electron fluid velocity. The hypersonic solution branch ceases to exist above a critical island width. Under normal circumstances, both types of island are stabilized by local ion polarization currents.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.55.Fa Tokamaks, spherical tokamaks

Interpretation of edge pedestal rotation measurements in DIII-D

W. M. Stacey and R. J. Groebner

Phys. Plasmas 15, 012503 (2008); http://dx.doi.org/10.1063/1.2830653 (11 pages) | Cited 17 times

Online Publication Date: 25 January 2008

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A novel methodology for inferring experimental toroidal angular momentum transfer rates from measured toroidal rotation velocities and other measured quantities has been developed and applied to analyze rotation measurements in the DIII-D [ J. Luxon, Nucl. Fusion 42, 6149 (2002) ] edge pedestal. The experimentally inferred values have been compared with predictions based on atomic physics processes and on neoclassical toroidal viscosity. The poloidal rotation velocities have been calculated from poloidal momentum balance using neoclassical parallel viscosity and a novel retention of all terms in the poloidal momentum balance, and compared with measured values in the DIII-D edge pedestal.
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52.55.Fa Tokamaks, spherical tokamaks
52.40.Hf Plasma-material interactions; boundary layer effects
52.30.-q Plasma dynamics and flow
52.25.Fi Transport properties

Estimation of pump-out and positive radial electric field created by electron cyclotron resonance heating in magnetic confinement devices

F. Castejón, S. Eguilior, I. Calvo, D. López-Bruna, and J. M. García-Regaña

Phys. Plasmas 15, 012504 (2008); http://dx.doi.org/10.1063/1.2831063 (8 pages) | Cited 3 times

Online Publication Date: 29 January 2008

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A fast approximate technique for calculating the outward electron flux induced by electron cyclotron resonance heating in magnetic confinement devices with ripple is presented. A model based on Langevin equations that allows one to compute the microscopic flux into the loss cone in momentum space is used. The outward macroscopic electron flux is also obtained for given plasma profiles. This extra flux causes the onset of a positive ambipolar electric field whose time evolution is demonstrated to depend strongly on the poloidal damping for electrons.
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52.25.Dg Plasma kinetic equations
52.70.-m Plasma diagnostic techniques and instrumentation
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.55.Jd Magnetic mirrors, gas dynamic traps
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