| 11. |
- 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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| 12. |
- Brodin, Gert, 1963-, et al.
(författare)
-
Stimulated Brillouin scattering in magnetized plasmas
- 2013
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Ingår i: Journal of Plasma Physics. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 79:Special Issue 06, s. 983-986
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Tidskriftsartikel (refereegranskat)abstract
- Previous theory for stimulated Brillouin scattering is reconsidered and generalized. We introduce an effective ion sound velocity that turns out to be useful in describing scattering instabilities.
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| 13. |
- Brodin, Gert, et al.
(författare)
-
Three-wave coupling coefficients for perpendicular wave propagation in a magnetized plasma
- 2015
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 22:10
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Tidskriftsartikel (refereegranskat)abstract
- The resonant interaction between three waves in a uniform magnetized plasma is reconsidered. Starting from previous kinetic expressions, we limit our investigation to waves propagating perpendicularly to the external magnetic field. It is shown that reliable results can only be obtained in the two-dimensional case, i.e., when the wave vectors have both x and y components.
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| 14. |
- Brodin, Gert, et al.
(författare)
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Wave Generation in a Warm Magnetized Multi-Component Plasma
- 2014
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Ingår i: Contributions to Plasma Physics. - : Wiley. - 0863-1042 .- 1521-3986. ; 54:7, s. 623-625
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Tidskriftsartikel (refereegranskat)abstract
- The resonant interaction between three waves propagating perpendicularly to an external magnetic field in a plasma is considered. We present the explicit expressions for the three wave coupling coefficients of a warm multi-component plasma. The results of previous work on the generation of THz radiation by laser plasma interaction are significantly improved. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 15. |
- Dieckmann, Mark E, 1969-, et al.
(författare)
-
Simulation study of the filamentation of counter-streaming beams of the electrons and positrons in plasmas
- 2009
-
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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| 16. |
- Eliasson, Bengt, et al.
(författare)
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Full-scale simulation study of stimulated electromagnetic emissions: The first ten milliseconds
- 2010
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Ingår i: JOURNAL OF PLASMA PHYSICS. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 76, s. 369-375
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Tidskriftsartikel (refereegranskat)abstract
- A full-scale numerical study is performed of the nonlinear interaction between a large-amplitude electromagnetic wave and the Earths ionosphere; and of the stimulated electromagnetic emission emerging from the turbulent layer, during the first 10 milliseconds after switch-on of the radio transmitter. The frequency spectra are downshifted in frequency and appear to emerge from a region somewhat below the cutoff of the O mode, which is characterized by Langmuir wave turbulence and localized Langmuir envelopes trapped in ion density cavities. The spectral features of escaping O-mode waves are very similar to those observed in experiments. The frequency components of Z-mode waves, trapped in the region between the O- and Z-mode cutoffs show strongly asymmetric and downshifted spectra.
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| 17. |
- Eliasson, Bengt, et al.
(författare)
-
Full-scale simulation study of the initial stage of ionospheric turbulence
- 2008
-
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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| 18. |
- Kaladze, T D, et al.
(författare)
-
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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| 19. |
- Karimov, AR, et al.
(författare)
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Flow oscillations in radial expansion of an inhomogeneous plasma layer
- 2011
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Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:27, s. 2629-2636
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Tidskriftsartikel (refereegranskat)abstract
- The cylindrically symmetric radial evolution of an inhomogeneous plasma layer expanding into vacuum is investigated nonperturbatively by first determining the spatial structure of the plasma flow structure. The evolution is then governed by a set of ordinary differential equations. The effect of the plasma inhomogeneity on the nonlinear coupling among the electron and ion flow components and oscillations is investigated
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| 20. |
- Karimov, A R, et al.
(författare)
-
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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