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Dec 2004

Volume 11, Issue 12, pp. L77-L84, 5379-5736

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Random shearing by zonal flows and transport reduction

Eun-jin Kim and P. H. Diamond

Phys. Plasmas 11, L77 (2004); http://dx.doi.org/10.1063/1.1808455 (4 pages) | Cited 16 times

Online Publication Date: 29 October 2004

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The physics of random shearing by zonal flows and the consequent reduction of scalar field transport are studied. In contrast to mean shear flows, zonal flows have a finite autocorrelation time and can exhibit complex spatial structure. A random zonal flow with a finite correlation time τZF decorrelates two nearby fluid elements less efficiently than a mean shear flow does. The decorrelation time is τD = (τη/τZFΩrms2)1/2 (τη is the turbulent scattering time, and Ωrms is the rms shear), leading to larger scalar field amplitude with a slightly different scaling (∝τD/Ωrms), as compared to the case of coherent shearing. In the strong shear limit, the flux scales as ∝Ωrms−1.
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52.30.-q Plasma dynamics and flow
52.25.Fi Transport properties
52.35.Ra Plasma turbulence

Variational principles for stationary one- and two-fluid equilibria of axisymmetric laboratory and astrophysical plasmas

J. P. Goedbloed

Phys. Plasmas 11, L81 (2004); http://dx.doi.org/10.1063/1.1808453 (4 pages) | Cited 21 times

Online Publication Date: 17 November 2004

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It is shown that the core equations of both the magnetohydrodynamics and the two-fluid description of stationary axisymmetric equilibrium flows may be derived from variational principles in terms of the core variables of the respective descriptions. The latter replace the primitive variables because of the stream function constraints associated with axisymmetry. This yields a concise representation of stationary flows in tokamaks, accretion disks, and jets, and permits accurate numerical implementation. Since hyperbolic flows occur in both descriptions, the limitation of the variational principles to elliptic flow regimes presents an intricate problem.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
95.30.Qd Magnetohydrodynamics and plasmas
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
47.65.-d Magnetohydrodynamics and electrohydrodynamics
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back to top Lasers, Particle Beams, Accelerators, Radiation Generation

Effects of plasma density on relativistic self-injection for electron laser wake-field acceleration

A. Zhidkov, J. Koga, T. Hosokai, K. Kinoshita, and M. Uesaka

Phys. Plasmas 11, 5379 (2004); http://dx.doi.org/10.1063/1.1807849 (8 pages) | Cited 22 times

Online Publication Date: 29 October 2004

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Density effects on the dynamics of a cavity produced in the wake of an ultraintense (a0 = eE/mcω≫1) and short (ωplτ/π<1) laser pulse and on the duration of accelerated electrons are studied via two-dimensional particle-in-cell simulation. Formation of a nonbreaking cavity is a crucial part of relativistic self-injection of plasma electrons from the front of a laser pulse and their further acceleration leading to a beam-quality femtosecond bunch. This self-injection appears in a uniform plasma when the group velocity of the pulse becomes smaller than the maximal electron velocity accelerated in the ponderomotive bias, Φ = mc2a02/2. However with increasing density, this mechanism starts to contend with relativistic wave breaking. Though additional injection due to the relativistic wave breaking increases the total charge of energetic electrons, the duration of the bunch increases to the picosecond range and its energy distribution becomes a Maxwellian.
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52.27.Ny Relativistic plasmas
52.38.Kd Laser-plasma acceleration of electrons and ions
52.25.-b Plasma properties
52.65.Rr Particle-in-cell method
back to top Nonlinear Phenomena, Turbulence, Transport

The role of electron heat flux in guide-field magnetic reconnection

Michael Hesse, Masha Kuznetsova, and Joachim Birn

Phys. Plasmas 11, 5387 (2004); http://dx.doi.org/10.1063/1.1795991 (11 pages) | Cited 30 times

Online Publication Date: 29 October 2004

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A combination of analytical theory and particle-in-cell simulations are employed in order to investigate the electron dynamics near and at the site of guide field magnetic reconnection. A detailed analysis of the contributions to the reconnection electric field shows that both bulk inertia and pressure-based quasiviscous processes are important for the electrons. Analytic scaling demonstrates that conventional approximations for the electron pressure tensor behavior in the dissipation region fail, and that heat flux contributions need to be accounted for. Based on the evolution equation of the heat flux three tensor, which is derived in this paper, an approximate form of the relevant heat flux contributions to the pressure tensor is developed, which reproduces the numerical modeling result reasonably well. Based on this approximation, it is possible to develop a scaling of the electron current layer in the central dissipation region. It is shown that the pressure tensor contributions become important at the scale length defined by the electron Larmor radius in the guide magnetic field.
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52.25.Fi Transport properties
52.35.Vd Magnetic reconnection
52.65.Rr Particle-in-cell method
back to top Low-temperature Plasmas, Plasma Applications, Plasma Sources, Sheaths

Relativistic effects on the Weibel instability of circularly polarized microwave produced plasmas

B. Shokri and M. Ghorbanalilu

Phys. Plasmas 11, 5398 (2004); http://dx.doi.org/10.1063/1.1809119 (4 pages) | Cited 12 times

Online Publication Date: 29 October 2004

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Analyzing the production of a weakly relativistic plasma produced by microwave fields with circular polarization in the adiabatic approximation, the electron distribution function is obtained, which is nonequilibrium and anisotropic. Furthermore, it is shown that the produced plasma is accelerated in the direction of propagating microwave electric fields. The electron velocity in this direction strongly depends on electron origination phase, electric field phase, and amplitude of the microwave electric field. Making use of the dielectric tensor obtained for this plasma, it is shown that the Weibel instability develops due to the anisotropic property of the distribution function. It is shown that the growth rate in the relativistic case is higher than that obtained for the nonrelativistic case by a factor depending on the electric field strength and plasma frequency.
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52.27.Ny Relativistic plasmas
52.25.Mq Dielectric properties
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.25.Dg Plasma kinetic equations
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.50.-b Plasma production and heating

Characterization of a radio-frequency line-plasma source in longitudinal line cusps created by permanent magnets

Youichi Sakawa, Kentaro Yano, and Tatsuo Shoji

Phys. Plasmas 11, 5402 (2004); http://dx.doi.org/10.1063/1.1809120 (7 pages)

Online Publication Date: 29 October 2004

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Characterization of a compact, high density, and uniform rf line-plasma source has been investigated. Plasma production is conducted in a rectangular discharge chamber (200×100×20 mm3) with a pair of permanent magnets placed on top and bottom of the chamber. A rf current is applied to an internal antenna covered with a quartz tube, and the plasma is produced by an inductive rf discharge. A magnetic field B0 structure of longitudinal line cusps is produced around the edge of the magnets. Ion-saturation current-density Jis profile is controlled by varying the width of the magnets and/or the distance between the antenna and the magnets, because the electrons created in the low-B0 region are reflected in the high-B0 region. The measured Jis profiles are explained by solving the equation of motion for electrons under the cusped magnetic field. A 140 mm wide plasma [plasma density ≃ (1.8–2.5)×1012 cm−3 for electron temperature = 4–8 eV] of a uniformity variation within 90% is produced using a 140 mm long antenna for an Ar pressure of 20 mTorr and a rf power of 3 kW.
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52.50.Dg Plasma sources
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.80.Pi High-frequency and RF discharges
28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium
52.25.Fi Transport properties
back to top Magnetically Confined Plasmas, Heating, Confinement

On the stabilization of fast magnetoacoustic waves by toroidally trapped energetic ions

V. S. Belikov, Ya. I. Kolesnichenko, and R. B. White

Phys. Plasmas 11, 5409 (2004); http://dx.doi.org/10.1063/1.1809121 (4 pages) | Cited 1 time

Online Publication Date: 29 October 2004

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A theory of the trapped-particle-driven fast magnetoacoustic instability with the frequency below the ion gyrofrequency in toroidal plasmas is developed. It is shown that the l = 0 resonance (where l is the number of the cyclotron harmonic), which was ignored in previous theories, typically has a strong stabilizing influence on the instability. It is concluded that the fast magnetoacoustic instability observed in the National Spherical Torus Experiment [E. Fredrickson, N. N. Gorelenkev, C. Z. Cheng et al., Phys. Rev. Lett. 87, 145001 (2001)] is caused by the circulating energetic ions only.
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52.55.Fa Tokamaks, spherical tokamaks
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

Investigation of self-organized criticality behavior of edge plasma transport in Torus experiment of technology oriented research

Y. H. Xu, S. Jachmich, R. R. Weynants, A. Huber, B. Unterberg, and U. Samm

Phys. Plasmas 11, 5413 (2004); http://dx.doi.org/10.1063/1.1810160 (10 pages) | Cited 10 times

Online Publication Date: 29 October 2004

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The self-organized criticality (SOC) behavior of the edge plasma transport has been studied using fluctuation data measured in the plasma edge and the scrape-off layer of Torus experiment of technology oriented research tokamak [H. Soltwisch et al., Plasma Phys. Controlled Fusion 26, 23 (1984)] before and during the edge biasing experiments. In the “nonshear” discharge phase before biasing, the fluctuation data clearly show some of the characteristics associated with SOC, including similar frequency spectra to those obtained in “sandpile” transport and other SOC systems, slowly decaying long tails in the autocorrelation function, values of Hurst parameters larger than 0.5 at all the detected radial locations, and a radial propagation of avalanchelike events in the edge plasma area. During the edge biasing phase, with the generation of an edge radial electric field Er and thus of Er×B flow shear, contrary to theoretical expectation, the Hurst parameters are substantially enhanced in the negative flow shear region and in the scrape-off layer as well. Concomitantly, it is found that the local turbulence is well decorrelated by the Er×B velocity shear, consistent with theoretical predictions.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.30.-q Plasma dynamics and flow
52.55.Fa Tokamaks, spherical tokamaks
52.25.Fi Transport properties
52.50.Nr Plasma heating by DC fields; ohmic heating, arcs
52.35.Ra Plasma turbulence
05.65.+b Self-organized systems
05.45.Df Fractals
52.25.Gj Fluctuation and chaos phenomena
back to top Lasers, Particle Beams, Accelerators, Radiation Generation

Reflections in gyrotrons with radial output: Consequences for the ITER coaxial gyrotron

O. Dumbrajs, G. S. Nusinovich, and B. Piosczyk

Phys. Plasmas 11, 5423 (2004); http://dx.doi.org/10.1063/1.1810161 (7 pages) | Cited 1 time

Online Publication Date: 29 October 2004

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A theory describing the influence of reflections on operation of gyrotrons with radial output is presented. The theory is used for evaluating the effect of reflections on the operation of the 170 GHz ITER coaxial cavity gyrotron, which is under development in cooperation between EUROATOM Associations (CRPP Lausanne, FZK Karlsruhe, and HUT Helsinki) together with European tube industry (Thales Electron Devices, Velizy, France). It is shown that for optimally chosen external magnetic field value and electron beam radius, possible reflections do not change the final steady-state operation, which corresponds to generation of a 2.2 MW millimeter-wave power. The effect of deviation of the magnetic field and the beam radius from optimal values on the device operation is also studied.
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84.40.Ik Masers; gyrotrons (cyclotron-resonance masers)
back to top Nonlinear Phenomena, Turbulence, Transport

Thermal density fluctuations and correlations in homogeneous plasmas

R. D. Hazeltine and S. M. Mahajan

Phys. Plasmas 11, 5430 (2004); http://dx.doi.org/10.1063/1.1810515 (6 pages) | Cited 5 times

Online Publication Date: 29 October 2004

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The spatial correlation function for thermal plasma density fluctuations is computed from the plasma entropy. The method is demonstrated by three examples: a Maxwellian plasma, a strongly magnetized plasma, and a plasma dominated by Coulomb collisions. In each case the entropy is computed from the one-particle distribution function and then, following the Einstein method, used to construct the probability distribution for density fluctuation.
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52.25.Gj Fluctuation and chaos phenomena
52.20.Fs Electron collisions
52.25.Xz Magnetized plasmas
52.25.Kn Thermodynamics of plasmas
back to top Radiation: Emission, Absorption, Transport

Helium line intensity ratio in microwave-generated plasmas

N. K. Podder, J. A. Johnson, C. T. Raynor, S. D. Loch, C. P. Ballance, and M. S. Pindzola

Phys. Plasmas 11, 5436 (2004); http://dx.doi.org/10.1063/1.1812535 (8 pages) | Cited 12 times

Online Publication Date: 29 October 2004

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The line intensity ratio method provides a nonintrusive diagnostic for the measurement of electron temperature in microwave-generated plasmas. For optically thin plasmas of low density, a line intensity method using He I lines can often be used, and is based on the fact that the electron impact excitation rate coefficients for helium singlet and triplet states are insensitive to electron density but differ as a function of the electron temperature. Line intensity measurements are presented from microwave-generated helium plasmas. Both steady-state corona and collision-radiative theoretical models are used to evaluate the ground and excited state populations. The line ratio versus electron temperature obtained from both of these methods are compared with the results from measurements. However, it is not possible to diagnose the electron temperature from the line ratios alone due to the presence of significant opacity and nonnegligible 1s2s 3S metastable fraction in the plasma.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.Ds Electric and magnetic measurements
52.80.Hc Glow; corona
52.20.Fs Electron collisions
52.25.Fi Transport properties
back to top Magnetically Confined Plasmas, Heating, Confinement

Alfvén continuum and Alfvén eigenmodes in the National Compact Stellarator Experiment

O. P. Fesenyuk, Ya. I. Kolesnichenko, V. V. Lutsenko, R. B. White, and Yu. V. Yakovenko

Phys. Plasmas 11, 5444 (2004); http://dx.doi.org/10.1063/1.1806136 (8 pages) | Cited 3 times

Online Publication Date: 29 October 2004

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The Alfvén continuum (AC) in the National Compact Stellarator Experiment (NCSX) [G. H. Neilson et al., in Fusion Energy 2002, 19th Conference Proceedings, Lyon, 2002 (International Atomic Energy Agency, Vienna, 2003), Report IAEA-CN-94∕IC-1] is investigated with the AC code COBRA [Ya. I. Kolesnichenko et al., Phys. Plasmas 8, 491 (2001)]. The resonant interaction of Alfvén eigenmodes and the fast ions produced by neutral beam injection is analyzed. Alfvén eigenmodes residing in one of the widest gap of the NCSX AC, the ellipticity-induced gap, are studied with the code BOA-E [V. V. Lutsenko et al., in Fusion Energy 2002, 19th Conference Proceedings, Lyon, 2002 (International Atomic Energy Agency, Vienna, 2003), Report IAEA-CN-94-TH∕P3-16].
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.55.Jd Magnetic mirrors, gas dynamic traps
52.65.Kj Magnetohydrodynamic and fluid equation
back to top Nonlinear Phenomena, Turbulence, Transport

Nonlocal nonlinear electrostatic gyrofluid equations

D. Strintzi and B. Scott

Phys. Plasmas 11, 5452 (2004); http://dx.doi.org/10.1063/1.1807850 (10 pages) | Cited 14 times

Online Publication Date: 1 November 2004

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Building on Lagrangian field theory methods of fluid dynamics, we construct a set of equations for an electrostatic gyrofluid model which can treat arbitrarily nonlinear situations. Noether’s theorem is used to find the exact energy theorem satisfied by the equations. The exchange of energy between the E×B fluid drift and thermal/kinetic parts of the dynamics is recovered rigorously. Diamagnetic cancellations are inserted manually.
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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.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.25.Fi Transport properties
52.35.Ra Plasma turbulence
back to top Basic Plasma Phenomena, Waves, Instabilities

Amplification of axially symmetric magnetic field by Bohm particle diffusion

Tae-Yeon Lee and Chang-Mo Ryu

Phys. Plasmas 11, 5462 (2004); http://dx.doi.org/10.1063/1.1809640 (6 pages) | Cited 1 time

Online Publication Date: 1 November 2004

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The magnetic induction equation for an axially symmetric magnetic field reveals an interesting feature, when the Bohm plasma diffusion is incorporated. The 1/B dependence of Bohm diffusion allows the induction equation to transform into a simple heat equation which admits an exact solution when the plasma temperature is constant. When the diffusion velocity satisfies a certain condition, the axially symmetric magnetic field can be significantly enhanced.
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52.25.Fi Transport properties
back to top Nonlinear Phenomena, Turbulence, Transport

Two-dimensional fast reconnection in a fluid drift model

Bruce Scott and Franco Porcelli

Phys. Plasmas 11, 5468 (2004); http://dx.doi.org/10.1063/1.1811616 (7 pages) | Cited 7 times

Online Publication Date: 1 November 2004

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A simple scenario for two-dimensional reconnection is reexamined in the context of a fluid drift model which treats the pressure and parallel ion velocity independently. The rapid nonlinear establishment of an arbitrarily thin current sheet is unaffected for expected values of the plasma β of a few percent. Eventually the sound wave dynamics should enter to alter the results, but remains insignificant for reasonable β values (gas/magnetic pressure up to 0.1).
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52.35.Vd Magnetic reconnection
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.)
52.25.Fi Transport properties

Magnetic electron drift waves in electron magnetohydrodynamic plasmas

Nikhil Chakrabarti and Raghvendra Singh

Phys. Plasmas 11, 5475 (2004); http://dx.doi.org/10.1063/1.1815002 (5 pages)

Online Publication Date: 1 November 2004

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The dynamics of nonuniform, magnetized, cold electron plasma in a stationary charge neutral ion background is considered. In the high frequency limit, electromagnetic modification of electron plasma oscillation is obtained in homogeneous plasma, whereas in inhomogeneous plasma in the low frequency regime a driftlike mode is found. Nonlinear evolution of this mode is derived to describe the two-dimensional (2D) dynamics. The equation has a close resemblance to 2D electrostatic collisionless drift wave equation thereby called as “magnetic electron drift” wave. In addition to the usual small amplitude dispersive modes the stationary state nonlinear vortexlike solutions are also discussed. The magnetic electron drift wave in the electron magnetohydrodynamic regime can find applications in laboratory as well as in space plasmas.
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52.35.Kt Drift waves
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.We Plasma vorticity
52.25.Ya Neutrals in plasmas
52.25.Xz Magnetized plasmas
back to top Magnetically Confined Plasmas, Heating, Confinement

Conventional δf-particle simulations of electromagnetic perturbations with finite elements

Alexey Mishchenko, Roman Hatzky, and Axel Könies

Phys. Plasmas 11, 5480 (2004); http://dx.doi.org/10.1063/1.1812275 (7 pages) | Cited 15 times

Online Publication Date: 2 November 2004

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The possibility of electromagnetic particle-in-cell simulations with a conventional δf approach is shown in slab geometry using finite elements. Both the ion-temperature-gradient driven mode and the shear Alfvén wave are reproduced and benchmarked with the analytical linear dispersion relation. Particularly, the Alfvén wave is simulated successfully at the limit k⊥→0.
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52.65.Rr Particle-in-cell method
02.70.Dh Finite-element and Galerkin methods
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

Edge pedestal structure

W. M. Stacey

Phys. Plasmas 11, 5487 (2004); http://dx.doi.org/10.1063/1.1808751 (10 pages) | Cited 6 times

Online Publication Date: 3 November 2004

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The hypothesis is advanced and it is investigated that, in between or in the absence of edge-localized modes, the structure of the edge pedestal is determined by the transport requirements of plasma particle, momentum and energy balance, and by recycling neutral atoms. A set of “pedestal equations” following from this hypothesis are presented and applied to calculate the edge density, temperature, rotation velocity, and radial electric field profiles in a DIII-D H (high)-mode plasma. It is found that a pedestal structure in the density profile and sharp negative peaks in the radial electric field and poloidal velocity just inside the separatrix are predicted as natural consequences of the conservation of particle and momentum, in qualitative and quantitative agreement with measured values. Detailed examination of the calculation reveals a sequence of mechanisms by which the ionization of recycling neutrals affect the structure of the density profile in the edge pedestal.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.55.Fa Tokamaks, spherical tokamaks
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.)
52.25.Ya Neutrals in plasmas
back to top Low-temperature Plasmas, Plasma Applications, Plasma Sources, Sheaths

Collisional radiative model of an argon atmospheric capillary surface-wave discharge

A. Yanguas-Gil, J. Cotrino, and A. R. González-Elipe

Phys. Plasmas 11, 5497 (2004); http://dx.doi.org/10.1063/1.1804972 (10 pages) | Cited 6 times

Online Publication Date: 3 November 2004

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The characteristics of a microwave surface-wave sustained plasma operated at atmospheric pressure in an open-ended dielectric tube are investigated theoretically as a first step in the development of a self-consistent model for these discharges. The plasma column is sustained in flowing argon. A surface-wave discharge that fills the whole radial cross section of the discharge tube is considered. With experimental electron temperature profiles [García et al., Spectrochim. Acta, Part B 55, 1733 (2000)] the numerical model is used to test the validity of the different approximations and to study the influence of the different kinetic processes and power loss mechanisms on the discharge.
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52.80.Pi High-frequency and RF discharges
back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

The effect of a short-wavelength mode on the evolution of a long-wavelength perturbation driven by a strong blast wave

A. R. Miles, M. J. Edwards, B. Blue, J. F. Hansen, H. F. Robey, R. P. Drake, C. Kuranz, and D. R. Leibrandt

Phys. Plasmas 11, 5507 (2004); http://dx.doi.org/10.1063/1.1812758 (13 pages) | Cited 7 times

Online Publication Date: 4 November 2004

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Shock-accelerated material interfaces are potentially unstable to both the Richtmyer–Meshkov and Rayleigh–Taylor (RT) instabilities. Shear that develops along with these instabilities in turn drives the Kelvin–Helmholtz instability. When driven by strong shocks, the evolution and interaction of these instabilities is further complicated by compressibility effects. This paper details a computational study of the formation of jets at strongly driven hydrodynamically unstable interfaces, and the interaction of these jets with one another and with developing spikes and bubbles. This provides a nonlinear spike-spike and spike-bubble interaction mechanism that can have a significant impact on the large-scale characteristics of the mixing layer. These interactions result in sensitivity to the initial perturbation spectrum, including the relative phases of the various modes, that persists long into the nonlinear phase of instability evolution. Implications for instability growth rates, the bubble merger process, and the degree of mix in the layer are described. Results from relevant deceleration RT experiments, performed on OMEGA [J. M. Soures et al., Phys. Plasmas 5, 2108 (1996)], are shown to demonstrate some of these effects.
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52.57.Fg Implosion symmetry and hydrodynamic instability (Rayleigh-Taylor, Richtmyer-Meshkov, imprint, etc.)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.75.-d Plasma devices
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
52.50.Lp Plasma production and heating by shock waves and compression
52.65.-y Plasma simulation
back to top Basic Plasma Phenomena, Waves, Instabilities

Theory for the breathing mode of a complex plasma disk

T. E. Sheridan

Phys. Plasmas 11, 5520 (2004); http://dx.doi.org/10.1063/1.1814366 (5 pages) | Cited 13 times

Online Publication Date: 5 November 2004

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A nonlinear equation of motion for the breathing-mode oscillation of a complex plasma disk is derived. Particles interact via a shielded Coulomb force with a Debye length λ and are confined in a parabolic potential well. Damping is due to the Epstein drag force. This system is modeled as a circular disk having uniform charge and mass densities. The equilibrium radius R0 and breathing frequency ωbr are calculated as a function of λ and d, the effective nearest-neighbor separation. For the unshielded Coulomb force (λ→∞), ωbr2 = 3. When R0/λ≪1, ωbr2−3 varies as (R0/λ)2. When R0/λ≫1, the value of ωbr depends on d. In the plasma regime d≪λ, ωbr2 ∼ 4, while in the nearest-neighbor regime d>λ, ωbr2 increases linearly with R0/λ with a slope proportional to d.
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52.27.Lw Dusty or complex plasmas; plasma crystals
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
back to top Magnetically Confined Plasmas, Heating, Confinement

Neoclassical dissipation and resistive wall modes in tokamaks

K. C. Shaing

Phys. Plasmas 11, 5525 (2004); http://dx.doi.org/10.1063/1.1806475 (7 pages) | Cited 18 times

Online Publication Date: 5 November 2004

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It is shown that the critical toroidal plasma flow speed that is required to stabilize the resistive wall mode in tokamaks is reduced by a factor of the order of B/Bθ or of 1.265ε3/4B/Bθ depending on the plasma parameters when the perturbed neoclassical viscosity driven current is taken into account. Here, B is the magnetic field strength, Bθ is the poloidal magnetic field strength, and ε is the inverse aspect ratio. This effect is illustrated using an existing model for the resistive wall modes by including the neoclassical dissipation in the derivation of the dispersion relation. The derivation is based on fluid equations with the plasma viscosity, calculated using kinetic equation, as the closure. The reduction of the critical toroidal speed is a consequence of the parallel (to the magnetic field B) momentum equation when neoclassical viscosity becomes important. The results are compared with experimental observations in tokamaks.
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52.55.Fa Tokamaks, spherical tokamaks
52.55.Tn Ideal and resistive MHD modes; kinetic modes
back to top Ionospheric, Solar-system, and Astrophysical Plasmas

Covariant kinetic dispersion theory of linear waves in anisotropic plasmas. I. General dispersion relations, bi-Maxwellian distributions and nonrelativistic limits

R. Schlickeiser

Phys. Plasmas 11, 5532 (2004); http://dx.doi.org/10.1063/1.1806828 (15 pages) | Cited 39 times

Online Publication Date: 9 November 2004

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The properties of longitudinal and transverse oscillations in unmagnetized anisotropic plasmas of arbitrary composition are investigated on the basis of Maxwell equations and the relativistic Vlasov equation. The longitudinal and transverse dispersion relations for plasmas with arbitrary distribution functions are derived. These dispersion relations describe the linear response of the system to the initial perturbations and thus define all existing linear plasma modes in the system. By analytic continuation the dispersion relations in the whole complex frequency plane are constructed. The further analysis is restricted to the important case of anisotropic bi-Maxwellian equilibrium plasma distribution functions. Explicit forms of the relativistically correct longitudinal and transverse dispersion relations are derived that hold for any values of the plasma temperatures and the temperature anisotropy. In the limit of nonrelativistic plasma temperatures the longitudinal and transverse dispersion relations can be expressed in terms of the Fried and Conte plasma dispersion function, however, the dependence on frequency and wave numbers is markedly different from the standard noncovariant nonrelativistic analysis. Only in the strictly unphysical formal limit of an infinitely large speed of light c→∞ the nonrelativistic dispersion relations reduce to the standard noncovariant nonrelativistic dispersion relations.
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52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.27.Ny Relativistic plasmas
back to top Nonlinear Phenomena, Turbulence, Transport

Particle acceleration during the coalescence of two magnetic loops in electron-ion plasmas

Shinji Saito and Jun-ichi Sakai

Phys. Plasmas 11, 5547 (2004); http://dx.doi.org/10.1063/1.1810162 (10 pages) | Cited 6 times

Online Publication Date: 9 November 2004

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Electron and ion acceleration mechanisms during the coalescence process of two adjacent magnetic loops through cohelicity and counterhelicity magnetic reconnection are investigated by using a two-dimensional, electromagnetic, and relativistic particle-in-cell (PIC) simulation. Three types of acceleration mechanisms are found by the PIC simulations. (1) Electrons in a current sheet generated between two adjacent magnetic loops are accelerated by the electric field induced during the collisionless magnetic reconnection, and their energy spectrum is characterized by the power law. (2) Ions trapped in the front of fast magnetosonic shock waves generated during the coalescence process are promptly accelerated by the surfatron acceleration mechanism. (3) During the coalescence process through counterhelicity magnetic reconnection, ions outside the current sheet are accelerated by E×B drift, where the electrostatic fields E perpendicular to local magnetic field are generated by the collision between surrounding magnetic field barrier and electron-dominated jet from the current sheet. During the coalescence process through cohelicity magnetic reconnection, the electron energy spectrum in the current sheet is characterized by the power law whose index is about 5, while during the coalescence process through counterhelicity magnetic reconnection, the electron energy spectrum is characterized by the double power law whose indices are about 3.3 and 6. The simulation results obtained here are applied to the proton and electron acceleration during solar flares. The maximum energy of accelerated electrons reaches about 100 keV, while the maximum energy of accelerated protons by the surfatron acceleration mechanism is about 10 MeV for both cohelicity and counterhelicity case.
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52.75.Di Ion and plasma propulsion
52.35.Kt Drift waves
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Vd Magnetic reconnection
52.35.Tc Shock waves and discontinuities
52.65.Rr Particle-in-cell method
52.25.Fi Transport properties
96.60.qe Flares
back to top Magnetically Confined Plasmas, Heating, Confinement

Global structure of zonal flow and electromagnetic ion temperature gradient driven turbulence in tokamak plasmas

Naoaki Miyato, Yasuaki Kishimoto, and Jiquan Li

Phys. Plasmas 11, 5557 (2004); http://dx.doi.org/10.1063/1.1811088 (8 pages) | Cited 68 times

Online Publication Date: 9 November 2004

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Global characteristics of the coupled system of zonal flows and electromagnetic ion temperature gradient driven turbulence in tokamak plasmas are investigated using a global electromagnetic Landau fluid code. Zonal flow behavior changes with the safety factor q. In a low q region stationary zonal flows are excited and they suppress the turbulence effectively. Coupling between zonal flows and poloidally asymmetric pressure perturbations due to a geodesic curvature makes the zonal flows oscillatory in a high q region. Energy transfer from the oscillatory zonal flows to the turbulence via the poloidally asymmetric pressure perturbations is identified. Therefore in the high q region where the zonal flows are oscillatory, the zonal flows cannot quench the turbulence and turbulent transport is not suppressed completely. As for the zonal flow behavior, it is favorable for confinement improvement to make the low q region where the stationary zonal flows are dominant in tokamak plasmas.
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52.55.Fa Tokamaks, spherical tokamaks
52.35.Kt Drift waves
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.65.Tt Gyrofluid and gyrokinetic simulations
52.25.Fi Transport properties
52.35.Ra Plasma turbulence
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
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