| 1. |
- Stenflo, Lennart, et al.
(författare)
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Nonlinear beam generated plasma waves as a source for enhanced plasma and ion acoustic lines
- 2011
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Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 18:15, s. 052107-1-052107-14
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Tidskriftsartikel (refereegranskat)abstract
- Observations by, for instance, the EISCAT Svalbard Radar (ESR) demonstrate that the symmetry of the naturally occurring ion line in the polar ionosphere can be broken by an enhanced, nonthermal, level of fluctuations (naturally enhanced ion-acoustic lines, NEIALs). It was in many cases found that the entire ion spectrum can be distorted, also with the appearance of a third line, corresponding to a propagation velocity significantly slower than the ion acoustic sound speed. It has been argued that selective decay of beam excited primary Langmuir waves can explain some phenomena similar to those observed. We consider a related model, suggesting that a primary nonlinear process can be an oscillating two-stream instability, generating a forced low frequency mode that does not obey any ion sound dispersion relation. At later times, the decay of Langmuir waves can give rise also to enhanced asymmetric ion lines. The analysis is based on numerical results, where the initial Langmuir waves are excited by a cold dilute electron beam. By this numerical approach, we can detect fine details of the physical processes, in particular, demonstrate a strong space-time intermittency of the electron waves in agreement with observations. Our code solves the full Vlasov equation for electrons and ions, with the dynamics coupled through the electrostatic field derived from Poisson's equation. The analysis distinguishes the dynamics of the background and beam electrons. This distinction simplifies the analysis for the formulation of the weakly nonlinear analytical model for the oscillating two-stream instability. The results have general applications beyond their relevance for the ionospheric observations.
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| 2. |
- Brodin, Gert, 1963-, et al.
(författare)
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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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| 3. |
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| 4. |
- 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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| 5. |
- Shukla, Padma Kant, et al.
(författare)
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Magnetization of plasmas
- 2010
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Ingår i: New Frontiers in Advanced Plasma Physics. - : AIP. ; , s. 1-6
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Wecritically examine and evaluate several physical mechanisms that are responsiblefor the seed magnetic fields in plasmas. The plasma magnetizationis attributed to sources that foster motion of the backgroundplasma electrons against the ions. The resulting space charge electricfield and currents, in turn, are detrimental for the plasmamagnetization.
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| 6. |
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| 7. |
- Stenflo, Lennart, 1939-, et al.
(författare)
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Decay interactions involving two electrostatic waves and one arbitrary polarized wave in a magnetized plasma
- 2010
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X .- 1551-7616. ; 1306, s. 14-17
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that previously overlooked formulations of the general theory are highly useful when deriving concrete expressions for specific cases. We also point out that some previous results deduced directly from the basic plasma equations contain inappropriate approximations leading to unphysical results. Finally, the generalization to more elaborate plasma models, containing e.g. kinetic effects, is presented.
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| 8. |
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| 9. |
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| 10. |
- Stenflo, Lennart, 1939-, et al.
(författare)
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On the parametric decay of a circularly polarized wave
- 2011
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Ingår i: Journal of Plasma Physics. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 77:4, s. 431-435
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Tidskriftsartikel (refereegranskat)abstract
- The nonlinear decay of a circularly polarized wave is reconsidered. We deduce an explicit expression for the growth rate, and present it in a form which is significantly simpler than those of previous papers.
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