| 1. |
- Shukla, Nitin, et al.
(författare)
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The dust acoustic wave in a bounded dusty plasma with strong electrostatic interactions between dust grains
- 2011
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Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 375:17, s. 1809-1811
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Tidskriftsartikel (refereegranskat)abstract
- The dispersion relation for the dust acoustic wave (DAW) in an unmagnetized dusty plasma cylindrical waveguide is derived, accounting for strong electrostatic interactions between charged dust grains. It is found that the boundary effect limits the radial extent of the DAW. The present result should be helpful for understanding the frequency spectrum of the DAW in a dusty plasma waveguide with strongly coupled charged dust grains.
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| 2. |
- Misra, Amar P, et al.
(författare)
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Stability of two-dimensional ion-acoustic wave packets in quantum plasmas
- 2011
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Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 18:4, s. 042102-042109
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Tidskriftsartikel (refereegranskat)abstract
- The nonlinear propagation of two-dimensional (2D) quantum ion-acoustic waves (QIAWs) is studied in a quantum electron–ion plasma. By using a 2D quantum hydrodynamic model and the method of multiple scales, a new set of coupled nonlinear partial differential equations is derived which governs the slow modulation of the 2D QIAW packets. The oblique modulational instability (MI) is then studied by means of a corresponding nonlinear Schrödinger equation derived from the coupled nonlinear partial differential equations. It is shown that the quantum parameter H (ratio of the plasmon energy density to Fermi energy) shifts the MI domains around the kθ -plane, where k is the carrier wave number and θ is the angle of modulation. In particular, the ion-acoustic wave (IAW), previously known to be stable under parallel modulation in classical plasmas, is shown to be unstable in quantum plasmas. The growth rate of the MI is found to be quenched by the obliqueness of modulation. The modulation of 2D QIAW packets along the wave vector k is shown to be described by a set of Davey–Stewartson-like equations. The latter can be studied for the 2D wave collapse in dense plasmas. The predicted results, which could be important to look for stable wave propagation in laboratory experiments as well as in dense astrophysical plasmas, thus generalize the theory of MI of IAW propagations both in classical and quantum electron–ion plasmas.
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| 3. |
- Moslem, WM, et al.
(författare)
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The optimum shielding around a test charge in plasmas containing two negative ions
- 2011
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Ingår i: Journal of Plasma Physics. - : Cambridge University Press. - 0022-3778 .- 1469-7807. ; 77:5, s. 663-673
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Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on the progress in understanding the shielding around a test charge in the presence of ion-acoustic waves in multispecies plasmas, whose constituents are positive ions, two negative ions, and Boltzmann distributed electrons. By solving the linearized Vlasov equation with Poisson equation, the Debye-Huckel screening potential and wakefield (oscillatory) potential distribution around a test charge particle are derived. It is analytically found that both the Debye-Huckel potential and the wakefield potential are significantly modified due to the presence of two negative ions. The present results might be helpful to understand and to form new materials from plasmas containing two negative ions such as Xe(+) - F(-) - SF(6)(-) and Ar(+) - F(-) - SF(6)(-) plasmas, as well as to tackle extension of the test charge problem in multinegative ions' coagulation/agglomeration.
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| 4. |
- Onishchenko, O. G., et al.
(författare)
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Finite ion Larmor radius effects in magnetic curvature-driven Rayleigh-Taylor instability
- 2011
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Ingår i: AIP Conference Proceeding Joint ITER-IAEA-ICTP Advanced Workshop on Fusion and Plasma Physics. - : American Institute of Physics (AIP). - 9780735410411 ; , s. 68-73
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Incomplete finite ion Larmor radius stabilization of the magnetic Rayleigh-Taylor (RT)instability is investigated. In contrast to the previous studies the effects of both the gravity and magnetic field curvature are taken into account. New model hydrodynamic equations describing nonlinear flute waves with arbitrary spatial scales have been derived. Particular attention is paid to the waves with spatial scales of the order of the ion Larmor radius. In the linear approximation a Fourier transform of these equations yields a generalized dispersion relation for flute waves. The condition for gravity and magnetic curvature at which the instability cannot be stabilized by the finite ion Larmor radius effects is found. It is shown that in the absence of the magnetic curvature the complete stabilization arises due to the cancellation of gravitational and diamagnetic drifts. However, when the magnetic curvature drift is taken into account this synchronization is violated and the RT instability is stabilized at more complex conditions. Furthermore, the dependence of the instability growth rate on the equilibrium plasma parameters is investigated.
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| 5. |
- Sabry, R., et al.
(författare)
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On the generation of envelope solitons in the presence of excess superthermal electrons and positrons
- 2011
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Ingår i: Astrophysics and Space Science. - : Springer Science and Business Media LLC. - 0004-640X .- 1572-946X. ; 333:1, s. 203-208
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical model is presented to investigate the existence, formation, and possible realization of nonlinear envelope ion acoustic solitary waves which accompany collisionless electron-positron-ion plasmas with high-energy electrons and positrons (represented by kappa distribution). By employing the reductive perturbation method, the hydrodynamic model and the Poisson equation are reduced to nonlinear Schrodinger equation. The effects of the superthermal parameters, as well as ion-to-electron temperature ratio on the propagation and stability of the envelope solitary waves are examined. The superthermal parameters (ion-to-electron temperature ratio) give rise to instability (stability) of the solitary excitations, since the instability window is strongly modified. Finally, the present results should elucidate the excitation of the nonlinear ion-acoustic solitary wave packets in superthermal electron-positron-ion plasmas, particularly in interstellar medium.
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| 6. |
- Sabry, R., et al.
(författare)
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Three-dimensional nonlinear Schrodinger equation in electron-positron-ion magnetoplasmas
- 2011
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 18:3
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional ion-acoustic envelope soliton excitations in electron-positron-ion magnetoplasmas are interpreted. This is accomplished through the derivation of three-dimensional nonlinear Schrodinger equation, where the nonlinearity is balancing with the dispersive terms. The latter contains both an external magnetic field besides the usual plasma parameter effects. Based on the balance between the nonlinearity and the dispersion terms, the regions for possible envelope solitons are investigated indicating that new regimes for modulational instability of envelope ion-acoustic waves could be obtained, which cannot exist in the unmagnetized case. This will allow us to establish additional new regimes, different from the usual unmagnetized plasma, for envelope ion-acoustic waves to propagate in multicomponent plasma that may be observed in space or astrophysics.
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