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Feb 2013

Volume 20, Issue 2, Articles (02xxxx)

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Phys. Plasmas 20, 022303 (2013); http://dx.doi.org/10.1063/1.4790639 (12 pages)

Julio J. Martinell and Diego del-Castillo-Negrete
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back to top Ionospheric, Solar-System, and Astrophysical Plasmas

Generating vorticity and magnetic fields in plasmas in general relativity: Spacetime curvature drive

Felipe A. Asenjo, Swadesh M. Mahajan, and Asghar Qadir

Phys. Plasmas 20, 022901 (2013); http://dx.doi.org/10.1063/1.4792257 (8 pages) | Cited 1 time

Online Publication Date: 14 February 2013

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Using the generally covariant magnetofluid formalism for a hot plasma, a spacetime curvature driven mechanism for generating seed vorticity/magnetic field is presented. The “battery” owes its origin to the interaction between the gravity modified Lorentz factor of the fluid element and the inhomogeneous plasma thermodynamics. The general relativistic drive is evaluated for two simple cases: seed formation in a simplified model of a hot plasma accreting in stable orbits around a Schwarzschild black hole and for particles in free fall near the horizon. Some astrophysical applications are suggested.
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95.30.Qd Magnetohydrodynamics and plasmas
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
04.70.Bw Classical black holes
52.35.We Plasma vorticity
52.27.Ny Relativistic plasmas
52.25.Kn Thermodynamics of plasmas

Comparison between hybrid and fully kinetic models of asymmetric magnetic reconnection: Coplanar and guide field configurations

Nicolas Aunai, Michael Hesse, Seiji Zenitani, Maria Kuznetsova, Carrie Black, Rebekah Evans, and Roch Smets

Phys. Plasmas 20, 022902 (2013); http://dx.doi.org/10.1063/1.4792250 (10 pages) | Cited 2 times

Online Publication Date: 15 February 2013

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Magnetic reconnection occurring in collisionless environments is a multi-scale process involving both ion and electron kinetic processes. Because of their small mass, the electron scales are difficult to resolve in numerical and satellite data, it is therefore critical to know whether the overall evolution of the reconnection process is influenced by the kinetic nature of the electrons, or is unchanged when assuming a simpler, fluid, electron model. This paper investigates this issue in the general context of an asymmetric current sheet, where both the magnetic field amplitude and the density vary through the discontinuity. A comparison is made between fully kinetic and hybrid kinetic simulations of magnetic reconnection in coplanar and guide field systems. The models share the initial condition but differ in their electron modeling. It is found that the overall evolution of the system, including the reconnection rate, is very similar between both models. The best agreement is found in the guide field system, which confines particle better than the coplanar one, where the locality of the moments is violated by the electron bounce motion. It is also shown that, contrary to the common understanding, reconnection is much faster in the guide field system than in the coplanar one. Both models show this tendency, indicating that the phenomenon is driven by ion kinetic effects and not electron ones.
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52.65.Kj Magnetohydrodynamic and fluid equation
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.25.Dg Plasma kinetic equations
52.25.Fi Transport properties

Ponderomotive force in the presence of electric fields

G. V. Khazanov and E. N. Krivorutsky

Phys. Plasmas 20, 022903 (2013); http://dx.doi.org/10.1063/1.4789874 (5 pages)

Online Publication Date: 21 February 2013

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This paper presents averaged equations of particle motion in an electromagnetic wave of arbitrary frequency with its wave vector directed along the ambient magnetic field. The particle is also subjected to an math×math drift and a background electric field slowly changing in space and acting along the magnetic field line. The fields, wave amplitude, and the wave vector depend on the coordinate along the magnetic field line. The derivations of the ponderomotive forces are done by assuming that the drift velocity in the ambient magnetic field is comparable to the particle velocity. Such a scenario leads to new ponderomotive forces, dependent on the wave magnetic field intensity, and, as a result, to the additional energy exchange between the wave and the plasma particles. It is found that the parallel electric field can lead to the change of the particle-wave energy exchange rate comparable to that produced by the previously discussed ponderomotive forces.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.25.Fi Transport properties
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