| 1. |
- Brodin, Gert, 1963-, et al.
(författare)
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On the parametric decay of waves in magnetized plasmas
- 2009
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Ingår i: Journal of Plasma Physics. - Cambridge UK : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 75, s. 9-13
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We reconsider the theory for three-wave interactions in cold plasmas. In particular, we demonstrate that previously overlooked formulations of the general theory are highly useful when deriving concrete expressions for specific cases. We also pointout that many previous results deduced directly from the basic plasma equations contain inappropriate approximations leading to unphysical results. Finally, generalizations to more elaborate plasma models containing, for example, kinetic effects are given.
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| 2. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
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Simulation study of the filamentation of counter-streaming beams of the electrons and positrons in plasmas
- 2009
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Ingår i: Plasma Physics and Controlled Fusion. - : Institute of Physics Publishing (IOPP). - 0741-3335 .- 1361-6587. ; 51:6
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Tidskriftsartikel (refereegranskat)abstract
- The filamentation instability (FI) driven by two spatially uniform and counter-streaming beams of charged particles in plasmas is modelled by a particle-in-cell simulation. Each beam consists of electrons and positrons. The four species are equally dense and have the same temperature. The one-dimensional simulation direction is orthogonal to the beam velocity vector. The magnetic field grows spontaneously and rearranges the particles in space, such that the distributions of the electrons of one beam and the positrons of the second beam match. The simulation demonstrates that as a result no electrostatic field is generated by the magnetic field through its magnetic pressure gradient prior to its saturation. This electrostatic field would be repulsive at the centres of the filaments and limit the maximum charge and current density. The filaments of electrons and positrons in this simulation reach higher charge and current densities than in one with no positrons. The oscillations of the magnetic field strength induced by the magnetically trapped particles result in an oscillatory magnetic pressure gradient force. The latter interplays with the statistical fluctuations in the particle density and it probably enforces a charge separation, by which electrostatic waves grow after the FI has saturated.
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| 3. |
- Eliasson, Bengt, et al.
(författare)
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Full-scale simulation study of the initial stage of ionospheric turbulence
- 2008
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 113:0148-0227, s. A02305-1-A02305-9
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Tidskriftsartikel (refereegranskat)abstract
- We present a full-scale simulation of the nonlinear interaction between an intense electromagnetic wave and the Earth's ionosphere, by means of a generalized Zakharov model. The radio wave propagates from the neutral atmosphere into the ionospheric plasma layer and reaches the turning points of the ordinary and extraordinary wave modes. At the turning point of the ordinary mode, a parametric instability takes place in which the electromagnetic wave decays into an electron plasma wave and an ion acoustic wave with a typical wavelength of one meter. This is followed by collapse and caviton formation and trapping of the intense electron plasma wave. The cavitons lead to an efficient excitation of slow X (or Z) waves that propagate further into the denser ionospheric layer at higher altitudes. We use a realistic ion (oxygen) mass, length scales, and other plasma parameters. This numerical study should be useful for understanding the nonlinear interaction between intense radio waves and the ionosphere.
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| 4. |
- Kaladze, T D, et al.
(författare)
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Acoustic-gravity waves in the Earths ionosphere
- 2008
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 70:13, s. 1607-1616
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Tidskriftsartikel (refereegranskat)abstract
- Taking into account the existence of charged particles in the Earths ionosphere the propagation of acoustic-gravity waves is investigated. The influence of the Coriolis force is also taken into account. The weakly ionized ionospheric D, E, and F-layers are considered. The existence of a cut-off frequency at 2 Omega(0) (Omega(0) is the value of the angular velocity of the Earths rotation) is noted. It is shown that the linear waves are damped because of the Pedersen conductivity. When the acoustic-gravity waves are excited by external events (volcanic eruptions, earthquakes, lightning strikes, etc.) their amplitudes grow until self-organization of these waves into nonlinear vortex solitary structures is admitted. Taking into account the interaction of the induced ionospheric current with the geomagnetic field the governing nonlinear equations are deduced. The formation of dipole vortex solitary structures of low-frequency internal gravity waves is shown for the stable stratified ionosphere. The dynamic energy equation for such nonlinear structures is obtained. It is shown that nonlinear solitary vortical structures damp due to joule losses.
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| 5. |
- Karimov, A R, et al.
(författare)
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Coupled azimuthal and radial flows and oscillations in a rotating plasma
- 2009
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Ingår i: PHYSICS OF PLASMAS. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 16:6, s. 062313-
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear coupling between the radial, axial, and azimuthal flows in a cold rotating plasma is considered nonperturbatively by first constructing a basis solution for a rotating flow. Simple but exact solutions that describe an expanding plasma with oscillatory flow fields are then obtained. These solutions show that the energy in the radial and axial flow components can be transferred to the azimuthal component but not the vice versa. Nonlinear electron velocity oscillations in the absence of electron density oscillations at the same frequency are shown to exist.
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| 6. |
- Karimov, A R, et al.
(författare)
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Coupled flows and oscillations in asymmetric rotating plasmas
- 2009
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Ingår i: PHYSICS OF PLASMAS. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 16:10, s. 102303-
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear coupling among the radial, axial, and azimuthal flows in an asymmetric cold rotating plasma is considered nonperturbatively. Exact solutions describing an expanding or contracting plasma with oscillations are then obtained. It is shown that despite the flow asymmetry the energy in the radial and axial flow components can be transferred to the azimuthal component but not the vice versa, and that flow oscillations need not be accompanied by density oscillations. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3247875]
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| 7. |
- Marklund, Mattias, et al.
(författare)
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New quantum limits in plasmonic devices
- 2008
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Ingår i: Europhysics letters. - Les Ulis : EDP Sciences. - 0295-5075 .- 1286-4854. ; 84:1
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Tidskriftsartikel (refereegranskat)abstract
- Surface plasmon polaritons (SPPs) have recently been recognized as an important future technique for microelectronics. Such SPPs have been studied using classical theory. However, current state-of-the-art experiments are rapidly approaching nanoscales, and quantum effects can then become important. Here we study the properties of quantum SPPs at the interface between an electron quantum plasma and a dielectric material. It is shown that the effect of quantum broadening of the transition layer is most important. In particular, the damping of SPPs does not vanish even in the absence of collisional dissipation, thus posing a fundamental size limit for plasmonic devices. Consequences and applications of our results are pointed out.
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| 8. |
- Shukla, Nitin, et al.
(författare)
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Ion streaming instability in a quantum dusty magnetoplasma
- 2008
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 15:1070-664X, s. 044503-1-044503-3
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that a relative drift between the ions and the charged dust particles in a magnetized quantum dusty plasma can produce an oscillatory instability in a quantum dust acousticlike wave. The threshold and growth rate of the instability are presented. The result may explain the origin of low-frequency electrostatic fluctuations in semiconductors quantum wells. (C) 2008 American Institute of Physics.
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| 9. |
- Shukla, Nitin, et al.
(författare)
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Magnetization of a warm plasma by the nonstationary ponderomotive force of an electromagnetic wave
- 2009
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Ingår i: PHYSICAL REVIEW E. - : American Physical Society. - 1539-3755. ; 80, s. 027401-
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that magnetic fields can be generated in a warm plasma by the nonstationary ponderomotive force of a large-amplitude electromagnetic wave. In the present Brief Report, we derive simple and explicit results that can be useful for understanding the origin of the magnetic fields that are produced in intense laser-plasma interaction experiments.
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| 10. |
- Shukla, Nitin, et al.
(författare)
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Nonlinear electromagnetic wave equations for superdense magnetized plasmas
- 2009
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Ingår i: PHYSICS OF PLASMAS. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 16:7
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Tidskriftsartikel (refereegranskat)abstract
- By using the quantum hydrodynamic and Maxwell equations, we derive the generalized nonlinear electron magnetohydrodynamic, the generalized nonlinear Hall-MHD (HMHD), and the generalized nonlinear dust HMHD equations in a self-gravitating dense magnetoplasma. Our nonlinear equations include the self-gravitating, the electromagnetic, the quantum statistical electron pressure, as well as the quantum electron tunneling and electron spin forces. They are useful for investigating a number of wave phenomena including linear and nonlinear electromagnetic waves, as well as three-dimensional electromagnetic wave turbulence spectra and structures arising from mode coupling processes at nanoscales in dense quantum magnetoplasmas.
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