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May 2010

Volume 17, Issue 5, Articles (05xxxx)

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Phys. Plasmas 17, 053505 (2010); http://dx.doi.org/10.1063/1.3429675 (8 pages)

S. B. Leonov, Y. I. Isaenkov, A. A. Firsov, S. L. Nothnagel, S. F. Gimelshein, and M. N. Shneider
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Spheromak formation and sustainment by tangential boundary flows

Pablo Luis García-Martínez and Ricardo Farengo

Phys. Plasmas 17, 050701 (2010); http://dx.doi.org/10.1063/1.3398482 (4 pages)

Online Publication Date: 7 May 2010

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The nonlinear, resistive, three-dimensional magnetohydrodynamic equations are solved numerically to demonstrate the possibility of forming and sustaining a spheromak by forcing tangential flows at the plasma boundary. The method can be explained in terms of helicity injection. Several features previously observed in dc helicity injection experiments are reproduced and analyzed.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.55.Ip Spheromaks
52.65.Kj Magnetohydrodynamic and fluid equation
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back to top Basic Plasma Phenomena, Waves, Instabilities

Connection between the two branches of the quantum two-stream instability across the k space

A. Bret and F. Haas

Phys. Plasmas 17, 052101 (2010); http://dx.doi.org/10.1063/1.3400228 (5 pages) | Cited 1 time

Online Publication Date: 6 May 2010

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The stability of two quantum counterstreaming electron beams is investigated within the quantum plasma fluid equations for arbitrarily oriented wave vectors k. The analysis reveals that the two quantum two-stream unstable branches are indeed connected by a continuum of unstable modes with oblique wave vectors. Using the longitudinal approximation, the stability domain for any k is analytically explained, together with the growth rate.
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52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
41.75.−i
03.65.−w

Thermal convective and rotational instability in dissipative magnetohydrodynamics

Haijun Ren, Zhengwei Wu, Chao Dong, and Paul K. Chu

Phys. Plasmas 17, 052102 (2010); http://dx.doi.org/10.1063/1.3407626 (6 pages) | Cited 2 times

Online Publication Date: 7 May 2010

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The thermal convective and magnetorotational instability is investigated by means of magnetohydrodynamic equations including anisotropic viscosity and resistivity dissipative effects. Magnetic force lines are assumed to be initially isothermal and the heat is restricted to being primarily transported along the magnetic force lines. To obtain the analytic expressions for the growth rate and instability criteria, we neglect the cross-field resistivity by applying our result to the weakly ionized environment. Under this assumption, the general dispersion relation describing the local thermal convective and magnetorotational instability is derived. The effects on the dispersion relation due to anisotropic resistivity and viscosity are discussed. Both the resistivity and viscosity show stabilizing effect on the thermal convective and rotational instability but do not affect the instability criterion. The analytic expression governing the growth rate is presented for Prandtl number Pm = 1 case.
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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)
52.25.Kn Thermodynamics of plasmas
47.55.P- Buoyancy-driven flows; convection

Structures of diffusion regions in collisionless magnetic reconnection

Takayuki Umeda, Kentaro Togano, and Tatsuki Ogino

Phys. Plasmas 17, 052103 (2010); http://dx.doi.org/10.1063/1.3403345 (6 pages) | Cited 3 times

Online Publication Date: 7 May 2010

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Detailed structures of diffusion regions in two-dimensional collisionless magnetic reconnection are studied by using an electromagnetic Vlasov simulation. It has been well known that plasma number density decreases near the X-point of the reconnection. However, numerical thermal fluctuations exist in particle-in-cell simulations, and there is a possibility that detailed structures near the X-point diffuse numerically when the number of particles per cell is not enough. In the present study, a high-resolution two-dimensional Vlasov simulation is performed. It is found that electron number density in the electron diffusion region decreases to a hundredth of the initial value. Structures of electron diffusion region are determined by the local electron inertial length.
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52.35.Vd Magnetic reconnection
52.65.Ff Fokker-Planck and Vlasov equation
94.30.cp Magnetic reconnection

Numerical study of ion-cyclotron resonant interaction via hybrid-Vlasov simulations

Francesco Valentini, Antonio Iazzolino, and Pierluigi Veltri

Phys. Plasmas 17, 052104 (2010); http://dx.doi.org/10.1063/1.3420278 (8 pages) | Cited 1 time

Online Publication Date: 14 May 2010

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Hybrid Vlasov–Maxwell numerical simulations are used to investigate the collisionless resonant interaction of ions with ion-cyclotron waves in parallel propagation with respect to a background magnetic field. In linear regime, analytical results on wave damping, obtained by integrating the linearized Vlasov equation through the well-known characteristics method, are compared with the numerical results. Then, the ion heating process and the consequent generation of temperature anisotropy in the direction perpendicular to the background magnetic field are investigated numerically in detail. In nonlinear regime, the numerical results show that the distribution of particle velocities is strongly distorted due to the resonant ion-cyclotron interaction with the formation of diffusive plateaus in the longitudinal direction (with respect to the ambient field) and significantly departs from the Maxwellian equilibrium. These results are relevant in many plasma physics environments, such as the solar wind, where the process of ion-cyclotron heating and the generation of temperature anisotropy and non-Maxwellian velocity distributions are routinely recovered in many in situ measurements, or the laboratory plasmas, where the resonant interaction of ions with ion-cyclotron waves is the primary source of auxiliary heating in the confining apparatus.
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52.20.−j
52.25.Dg Plasma kinetic equations
52.65.−y
52.65.Ww Hybrid methods

Langmuir wave dispersion relation in non-Maxwellian plasmas

M. Ouazene and R. Annou

Phys. Plasmas 17, 052105 (2010); http://dx.doi.org/10.1063/1.3420243 (5 pages) | Cited 2 times

Online Publication Date: 18 May 2010

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The Langmuir wave dispersion relation is derived in partially ionized plasmas, where free electrons are confined to move in a nearest neighbor ions’ potential well. The equilibrium velocity distribution function experiences then, a departure from Maxwell distribution function. The effect of the non-Maxwellian character of the distribution function on the Langmuir phase and group velocities as well as the phase matching conditions and the nonlinear growth rate of decay instability is investigated. The proposed Langmuir wave dispersion relation is relevant to dense and cryogenic plasmas.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
02.50.-r Probability theory, stochastic processes, and statistics

Effect of two ion species on the propagation of shear Alfvén waves of small transverse scale

S. T. Vincena, G. J. Morales, and J. E. Maggs

Phys. Plasmas 17, 052106 (2010); http://dx.doi.org/10.1063/1.3422549 (13 pages) | Cited 2 times

Online Publication Date: 18 May 2010

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The results of a theoretical modeling study and experimental investigation of the propagation properties of shear Alfvén waves of small transverse scale in a plasma with two ion species are reported. In the two ion plasma, depending on the mass of the heavier species, ion kinetic effects can become prominent, and significant parallel electric fields result in electron acceleration. The theory predicts the appearance of frequency propagation gaps at the ion-ion hybrid frequency and between harmonics of the lower cyclotron frequency. Within these frequency bands spatial structures arise that mix the cone-propagation characteristics of Alfvén waves with radially expanding ion Bernstein modes. The experiments, performed at the Basic Plasma Science Facility (BaPSF) at UCLA, consist of the spatial mapping of shear waves launched by a loop antenna. Although a variety of two ion-species combinations were explored, only results from a helium-neon mix are reported. A clear signature of a shear wave propagation gap, as well as propagation between multiple harmonics, is found for this gas combination. The evanescence of shear waves beyond the reflection point at the ion-ion hybrid frequency in the presence of an axial magnetic field gradient is also documented.
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52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.72.+v Laboratory studies of space- and astrophysical-plasma processes

The lower hybrid wave cutoff: A case study in eikonal methods

A. S. Richardson, P. T. Bonoli, and J. C. Wright

Phys. Plasmas 17, 052107 (2010); http://dx.doi.org/10.1063/1.3400217 (12 pages) | Cited 4 times

Online Publication Date: 18 May 2010

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Eikonal, or ray tracing, methods are commonly used to estimate the propagation of radio frequency fields in plasmas. While the information gained from the rays is quite useful, an approximate solution for the fields would also be valuable, e.g., for comparison to full wave simulations. Such approximations are often difficult to perform numerically because of the special care which must be taken to correctly reconstruct the fields near reflection and focusing caustics. In this paper, we compare the standard eikonal method for approximating fields to a method based on the dynamics of wave packets. We compare the approximations resulting from these two methods to the analytical solution for a lower hybrid wave reflecting from a cutoff. The algorithm based on wave packets has the advantage that it can correctly deal with caustics, without any special treatment.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
42.15.Dp Wave fronts and ray tracing

Scaling of asymmetric reconnection in compressible plasmas

J. Birn, J. E. Borovsky, M. Hesse, and K. Schindler

Phys. Plasmas 17, 052108 (2010); http://dx.doi.org/10.1063/1.3429676 (11 pages) | Cited 5 times

Online Publication Date: 19 May 2010

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The scaling of the reconnection rate with external parameters is reconsidered for antiparallel reconnection in a single-fluid magnetohydrodynamic (MHD) model, allowing for compressibility as well as asymmetry between the plasmas and magnetic fields in the two inflow regions. The results show a modest dependence of the reconnection rate on the plasma beta (ratio of plasma to magnetic pressure) in the inflow regions and demonstrate the importance of the conversion of magnetic energy to enthalpy flux (that is, convected thermal energy) in the outflow regions. The conversion of incoming magnetic to outgoing thermal energy flux remains finite even in the limit of incompressibility, while the scaling of the reconnection rate obtained earlier [ P. A. Cassak and M. A. Shay, Phys. Plasmas 14, 102114 (2007) ] is recovered. The assumptions entering the scaling estimates are critically investigated on the basis of two-dimensional resistive MHD simulations, confirming and even strengthening the importance of the enthalpy flux in the outflow from the reconnection site.
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52.35.Vd Magnetic reconnection
52.65.Kj Magnetohydrodynamic and fluid equation
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

Linear plasmoid instability of thin current sheets with shear flow

Lei Ni, Kai Germaschewski, Yi-Min Huang, Brian P. Sullivan, Hongang Yang, and Amitava Bhattacharjee

Phys. Plasmas 17, 052109 (2010); http://dx.doi.org/10.1063/1.3428553 (7 pages) | Cited 7 times

Online Publication Date: 27 May 2010

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This paper presents linear analytical and numerical studies of plasmoid instabilities in the presence of shear flow in high-Lundquist-number plasmas. Analysis demonstrates that the stability problem becomes essentially two dimensional as the stabilizing effects of shear flow become more prominent. Scaling results are presented for the two-dimensional instabilities. An approximate criterion is given for the critical aspect ratio of thin current sheets at which the plasmoid instability is triggered.
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52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
52.30.-q Plasma dynamics and flow
back to top Nonlinear Phenomena, Turbulence, Transport

Envelope ion-acoustic solitary waves in a plasma with positive-negative ions and nonthermal electrons

S. A. Elwakil, E. K. El-Shewy, and H. G. Abdelwahed

Phys. Plasmas 17, 052301 (2010); http://dx.doi.org/10.1063/1.3383052 (6 pages) | Cited 1 time

Online Publication Date: 3 May 2010

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Modulation instability of ion-acoustic waves is investigated in a plasma composed of positive and negative ions as well as nonthermal electrons. For this purpose, a linear dispersion relation and a nonlinear Schrödinger equation are derived. The latter admits localized envelope solitary wave solutions of bright-(pulses) and dark-(holes, voids) type. The envelope soliton depends on the intrinsic plasma parameters. It is found that modulation instability of ion-acoustic waves is significantly affected by the presence of nonthermal electrons. The present model is used to investigate the solitary excitations in the (H+,O2−) and (H+,H−) plasmas, where they are presented in the D-region and F-region of the Earth’s ionosphere. The findings of this investigation should be useful in understanding the stable electrostatic wave packet acceleration mechanisms in positive-negative ion plasmas, and also enhance our knowledge on the occurrence of instability associated to the propagation of the envelope ion-acoustic solitary waves in space and in laboratory plasmas where two distinct groups of ions and non-Boltzmann distributed electrons are present.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Sb Solitons; BGK modes
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
94.20.de D region
94.20.dj F region
94.05.Fg Solitons and solitary waves

Dressed electrostatic solitary waves in quantum dusty pair plasmas

M. Akbari-Moghanjoughi

Phys. Plasmas 17, 052302 (2010); http://dx.doi.org/10.1063/1.3392289 (9 pages) | Cited 11 times

Online Publication Date: 6 May 2010

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Quantum-hydrodynamics model is applied to investigate the nonlinear propagation of electrostatic solitary excitations in a quantum dusty pair plasma. A Korteweg de Vries evolution equation is obtained using reductive perturbation technique and the higher-nonlinearity effects are derived by solving the linear inhomogeneous differential equation analytically using Kodama–Taniuti renormalizing method. The possibility of propagation of bright- and dark-type solitary excitations is examined. It is shown that a critical value of quantum diffraction parameter H exists, on either side of which, only one type of solitary propagation is possible. It is also found that unlike for the first-order amplitude component, the variation of H parameter dominantly affects the soliton amplitude in higher-order approximation. The effect of fractional quantum number density on compressive and rarefactive soliton dynamics is also discussed.
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52.30.Ex Two-fluid and multi-fluid plasmas
52.35.−g
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.)

Large amplitude relativistic plasma waves

Timothy Coffey

Phys. Plasmas 17, 052303 (2010); http://dx.doi.org/10.1063/1.3418351 (8 pages) | Cited 2 times

Online Publication Date: 7 May 2010

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Relativistic, longitudinal plasma oscillations are studied for the case of a simple water bag distribution of electrons having cylindrical symmetry in momentum space with the axis of the cylinder parallel to the velocity of wave propagation. The plasma is required to obey the relativistic Vlasov–Poisson equations, and solutions are sought in the wave frame. An exact solution for the plasma density as a function of the electrostatic field is derived. The maximum electric field is presented in terms of an integral over the known density. It is shown that when the perpendicular momentum is neglected, the maximum electric field approaches infinity as the wave phase velocity approaches the speed of light. It is also shown that for any nonzero perpendicular momentum, the maximum electric field will remain finite as the wave phase velocity approaches the speed of light. The relationship to previously published solutions is discussed as is some recent controversy regarding the proper modeling of large amplitude relativistic plasma waves.
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52.27.Ny Relativistic plasmas
52.35.−g
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.)

Test particle analysis in L- and H-mode simulations

G. Sánchez Burillo, B. Ph. van Milligen, and A. Thyagaraja

Phys. Plasmas 17, 052304 (2010); http://dx.doi.org/10.1063/1.3392290 (10 pages) | Cited 3 times

Online Publication Date: 7 May 2010

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In this work, the radial transport of tracers in an H-mode run in the CUTIE code [ A. Thyagaraja et al., Phys. Plasmas 12, 090907 (2005) ] is analyzed globally. Several techniques are applied to the study of the trajectories performed by the tracers, measuring the degree of self-similarity in the motion and searching for long range spatial and temporal correlations. The results are compared to those of an L-mode run [ G. Sánchez Burillo et al., Phys. Plasmas 16, 042319 (2009) ] in order to highlight the changes between L and H. The analysis of self-similarity parameters of the motion reveals that changes, if any, are slight, although the reliability of the results is limited. Nevertheless, the study of the mean step size indicates that transport is more local (or rather less global) and the anomalous diffusion contribution is less dominant. Namely, the variance of the radial distribution of tracers is smaller in H-mode and the strong asymmetry in the positive/negative steps performed by the tracers vanishes.
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52.25.Fi Transport properties
52.55.Fa Tokamaks, spherical tokamaks
52.65.Kj Magnetohydrodynamic and fluid equation

Interface width effect on the classical Rayleigh–Taylor instability in the weakly nonlinear regime

L. F. Wang, W. H. Ye, and Y. J. Li

Phys. Plasmas 17, 052305 (2010); http://dx.doi.org/10.1063/1.3396369 (6 pages) | Cited 9 times

Online Publication Date: 7 May 2010

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In this paper, the interface width effects (i.e., the density gradient effects or the density transition layer effects) on the Rayleigh–Taylor instability (RTI) in the weakly nonlinear (WN) regime are investigated by numerical simulation (NS). It is found that the interface width effects dramatically influence the linear growth rate in the linear growth regime and the mode coupling process in the WN growth regime. First, the interface width effects decrease the linear growth rate of the RTI, particularly for the short perturbation wavelengths. Second, the interface width effects suppress (reduce) the third-order feedback to the fundamental mode, which induces the nonlinear saturation amplitude (NSA) to exceed the classical prediction, 0.1λ. The wider the density transition layer is, the larger the NSA is. The NSA in our NS can reach a half of its perturbation wavelength. Finally, the interface width effects suppress the generation and the growth of the second and the third harmonics. The ability to suppress the harmonics’ growth increases with the interface width but decreases with the perturbation wavelength. On the whole, in the WN regime, the interface width effects stabilize the RTI, except for an enhancement of the NSA, which is expected to improve the understanding of the formation mechanism for the astrophysical jets, and for the jetlike long spikes in the high energy density physics.
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52.57.Fg Implosion symmetry and hydrodynamic instability (Rayleigh-Taylor, Richtmyer-Meshkov, imprint, etc.)
47.20.Ma Interfacial instabilities (e.g., Rayleigh-Taylor)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

Nonlinear studies of fast electron current pulse propagation in a two dimensional inhomogeneous plasma

Sharad Kumar Yadav and Amita Das

Phys. Plasmas 17, 052306 (2010); http://dx.doi.org/10.1063/1.3407621 (9 pages) | Cited 1 time

Online Publication Date: 7 May 2010

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The evolution of fast current and magnetic field pulse structures through an inhomogeneous plasma medium was reported in recent publications [ Yadav et al., Phys. Plasmas 15, 062308 (2008) ; Yadav et al., Phys. Plasmas 16, 040701 (2009) ]. The evolution characteristics have been investigated here in further detail. Following specific issues have been addressed; (i) characterization of the phenomena of trapping versus transmission of the current pulse structures through a high density plasma region, (ii) interaction of the current pulse with plasma density inhomogeneity at various incidence angles, and (iii) destabilization of sharp sheared current layers resulting from the interaction with an elongated plasma density inhomogeneity. It is also illustrated that the destabilization of the current pulse trapped in an elongated high density plasma region forms a novel stable coherent nonlinear pattern of alternating signed vortices arranged as beads along the density profile.
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52.25.Fi Transport properties
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.)

The third-order law for magnetohydrodynamic turbulence with shear: Numerical investigation

M. Wan, S. Servidio, S. Oughton, and W. H. Matthaeus

Phys. Plasmas 17, 052307 (2010); http://dx.doi.org/10.1063/1.3398481 (9 pages) | Cited 1 time

Online Publication Date: 12 May 2010

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The scaling laws of third-order structure functions for isotropic, homogeneous, and incompressible magnetohydrodynamic (MHD) turbulence relate the observable structure function with the energy dissipation rate. Recently [ Wan et al. Phys. Plasmas 16, 090703 (2009) ], the theory was extended to the case in which a constant velocity shear is present, motivated by the application of the third-order law to the solar wind. We use direct numerical simulations of two-dimensional MHD with shear to confirm this new generalization of the theory. The presence of the shear effect broadens the circumstances in which the law can be applied. Important implications for laboratory and space plasmas are discussed.
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52.35.Ra Plasma turbulence
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.65.Kj Magnetohydrodynamic and fluid equation
02.60.Cb Numerical simulation; solution of equations

Perpendicular propagating electromagnetic envelope solitons in electron-positron-ion plasma

Nusrat Jehan, M. Salahuddin, and Arshad M. Mirza

Phys. Plasmas 17, 052308 (2010); http://dx.doi.org/10.1063/1.3414348 (11 pages) | Cited 1 time

Online Publication Date: 13 May 2010

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The nonlinear amplitude modulation of electromagnetic waves propagating perpendicular to the direction of ambient magnetic field in a uniform collisionless magnetized electron-positron-ion plasma is studied. The Krylov–Bogoliubov–Mitropolsky perturbation method is employed to derive nonlinear Schrödinger equation, which describes the amplitude dynamics of perturbed magnetic field. The modulation instability criterion reveals that the low frequency mode is always stable, whereas the high frequency mode becomes modulationally unstable for certain ranges of wave number and positron-to-electron density ratio. Furthermore, the positron-to-electron density ratio as well as the strength of ambient magnetic field is found to have significant effect on the solitary wave solutions of the nonlinear Schrödinger equation, namely, dark and bright envelope solitons.
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.35.Sb Solitons; BGK modes
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.-b Plasma properties

Study of the change of electron temperature inside magnetic island caused by localized radio frequency heating

J. Yang, S. Zhu, Q. Yu, and G. Zhuang

Phys. Plasmas 17, 052309 (2010); http://dx.doi.org/10.1063/1.3418372 (7 pages) | Cited 1 time

Online Publication Date: 14 May 2010

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The change in the electron temperature inside magnetic island caused by localized radio frequency (rf) heating is studied numerically by solving the two-dimensional energy transport equation, to investigate the dependence of the temperature change on the location and width of the rf power deposition along the minor radius and the helical angle, the island width, and the ratio between the parallel and the perpendicular heat conductivity. Based on obtained numerical results, suggestions for optimizing the island stabilization by localized rf heating are made.
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52.25.-b Plasma properties
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.55.Fa Tokamaks, spherical tokamaks

Three dimensional character of whistler turbulence

Gurudas Ganguli, Leonid Rudakov, Wayne Scales, Joseph Wang, and Manish Mithaiwala

Phys. Plasmas 17, 052310 (2010); http://dx.doi.org/10.1063/1.3420245 (8 pages) | Cited 5 times

Online Publication Date: 18 May 2010

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It is shown that the dominant nonlinear effect makes the evolution of whistler turbulence essentially three dimensional in character. Induced nonlinear scattering due to slow density perturbation resulting from ponderomotive force triggers energy flux toward lower frequency. Anisotropic wave vector spectrum is generated by large angle scatterings from thermal plasma particles, in which the wave propagation angle is substantially altered but the frequency spectrum changes a little. As a consequence, the wave vector spectrum does not indicate the trajectory of the energy flux. There can be conversion of quasielectrostatic waves into electromagnetic waves with large group velocity, enabling convection of energy away from the region. We use a two-dimensional electromagnetic particle-in-cell model with the ambient magnetic field out of the simulation plane to generate the essential three-dimensional nonlinear effects.
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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.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
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
52.65.Rr Particle-in-cell method

Full electromagnetic Vlasov code simulation of the Kelvin–Helmholtz instability

Takayuki Umeda, Jun-ichiro Miwa, Yosuke Matsumoto, Takuma K. M. Nakamura, Kentaro Togano, Keiichiro Fukazawa, and Iku Shinohara

Phys. Plasmas 17, 052311 (2010); http://dx.doi.org/10.1063/1.3422547 (10 pages) | Cited 4 times

Online Publication Date: 18 May 2010

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Recent advancement in numerical techniques for Vlasov simulations and their application to cross-scale coupling in the plasma universe are discussed. Magnetohydrodynamic (MHD) simulations are now widely used for numerical modeling of global and macroscopic phenomena. In the framework of the MHD approximation, however, diffusion coefficients such as resistivity and adiabatic index are given from empirical models. Thus there are recent attempts to understand first-principle kinetic processes in macroscopic phenomena, such as magnetic reconnection and the Kelvin–Helmholtz (KH) instability via full kinetic particle-in-cell and Vlasov codes. In the present study, a benchmark test for a new four-dimensional full electromagnetic Vlasov code is performed. First, the computational speed of the Vlasov code is measured and a linear performance scaling is obtained on a massively parallel supercomputer with more than 12 000 cores. Second, a first-principle Vlasov simulation of the KH instability is performed in order to evaluate current status of numerical techniques for Vlasov simulations. The KH instability is usually adopted as a benchmark test problem for guiding-center Vlasov codes, in which a cyclotron motion of charged particles is neglected. There is not any full electromagnetic Vlasov simulation of the KH instability; this is because it is difficult to follow math×math drift motion accurately without approximations. The present first-principle Vlasov simulation has successfully represented the formation of KH vortices and its secondary instability. These results suggest that Vlasov code simulations would be a powerful approach for studies of cross-scale coupling on future Peta-scale supercomputers.
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52.65.−y
52.65.Ff Fokker-Planck and Vlasov equation
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Ra Plasma turbulence
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)

An alternate approach to study electrostatic solitary waves in homogeneous and inhomogeneous quantum magnetoplasmas

W. Masood

Phys. Plasmas 17, 052312 (2010); http://dx.doi.org/10.1063/1.3422548 (5 pages) | Cited 2 times

Online Publication Date: 26 May 2010

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Ion acoustic drift solitary wave is studied in both linear and nonlinear regimes in an electron-ion quantum magnetoplasma. It is shown that using the linear dispersion relation, nonlinear Zakharov–Kuznetsov (ZK) equation can be derived in an inhomogeneous quantum magnetoplasma for ion acoustic drift solitary wave in a certain parametric range. The solution of the ZK equation is also presented using the tangent hyperbolic method. It is found that the quantum Bohm potential (via increasing number density), angle of propagation, and the magnetic field affect the propagation characteristics of the nonlinear quantum ion acoustic drift wave. The results presented in this paper may be beneficial to understand the formation of electrostatic drift solitary waves in dense magnetized plasmas.
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52.27.Ep Electron-positron plasmas
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Tc Shock waves and discontinuities

Two-dimensional bispectral analysis of drift wave turbulence in a cylindrical plasma

T. Yamada, S.-I. Itoh, S. Inagaki, Y. Nagashima, S. Shinohara, N. Kasuya, K. Terasaka, K. Kamataki, H. Arakawa, M. Yagi, A. Fujisawa, and K. Itoh

Phys. Plasmas 17, 052313 (2010); http://dx.doi.org/10.1063/1.3429674 (10 pages) | Cited 8 times

Online Publication Date: 27 May 2010

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Bispectral analysis and multichannel measurement are becoming attractive investigation tools in plasma fluctuation studies. In the Large Mirror Device-Upgrade, the measurement of fluctuations in the ion saturation-current with a 64-channel poloidal Langmuir probe array was performed. The two-dimensional (2D) (poloidal wave number and frequency) power spectrum showed a number of pronounced peaks and broadband fluctuations in the poloidal wave number-frequency space. We applied 2D bispectral analysis, which considers both the matching conditions of poloidal wave number and frequency, to the spatiotemporal waveform, and confirmed the nonlinear couplings between coherent-coherent, coherent-broadband, and broadband-broadband fluctuation components. More than ten peaks were revealed to have as their origins only three original parent modes generated in the plasma. Comparison between the theoretical estimate and experimental observation for the bicoherence showed good agreement.
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52.35.Kt Drift waves
52.35.Ra Plasma turbulence
52.70.Ds Electric and magnetic measurements
52.25.Gj Fluctuation and chaos phenomena
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

Two dimensional electrostatic shock waves in relativistic electron positron ion plasmas

W. Masood and H. Rizvi

Phys. Plasmas 17, 052314 (2010); http://dx.doi.org/10.1063/1.3439684 (6 pages) | Cited 4 times

Online Publication Date: 28 May 2010

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Ion-acoustic shock waves (IASWs) are studied in an unmagnetized plasma consisting of electrons, positrons and hot ions. In this regard, Kadomtsev–Petviashvili–Burgers (KPB) equation is derived using the small amplitude perturbation expansion method. The dependence of the IASWs on various plasma parameters is numerically investigated. It is observed that ratio of ion to electron temperature, kinematic viscosity, positron concentration, and the relativistic ion streaming velocity affect the structure of the IASW. Limiting case of the KPB equation is also discussed. Stability of KPB equation is also presented. The present investigation may have relevance in the study of electrostatic shock waves in relativistic electron-positron-ion plasmas.
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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.Tc Shock waves and discontinuities
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.30.Ex Two-fluid and multi-fluid plasmas
52.25.Xz Magnetized plasmas
back to top Magnetically Confined Plasmas, Heating, Confinement

Comparison between cylindrical model and experimental observation on the study of resistive wall mode in reversed field pinch plasmas

Z. R. Wang, S. C. Guo, L. Shi, T. Bolzonella, M. Baruzzo, and X. G. Wang

Phys. Plasmas 17, 052501 (2010); http://dx.doi.org/10.1063/1.3389229 (12 pages) | Cited 7 times

Online Publication Date: 7 May 2010

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A cylindrical magnetohydrodynamic model including plasma pressure and longitudinal flow has been employed for the study of resistive wall mode (RWM) in reversed field pinch (RFP) plasmas. In order to validate the model, a careful comparison with the experimental measurements in RFX-mod [ P. Sonato et al., Fusion Eng. Des. 66–68, 161 (2003) ] on the mode growth rates has been made by well matching the equilibrium parameters F, Θ, and βp. The RWM instability spectrum, which varies with the equilibrium parameters, is also calculated for comparison. The sensitivity of the mode growth rate to the equilibrium parameters is studied in details. It is concluded that the model can provide consistent accuracy in studies of RWM in RFP plasmas. The analysis based on the balance of the potential energy components has been carried out in order to obtain the physical understanding on the mode behavior.
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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)
52.40.Hf Plasma-material interactions; boundary layer effects
52.55.Tn Ideal and resistive MHD modes; kinetic modes
52.55.Ez Theta pinch
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