| 1. |
- Shukla, Nitin, et al.
(författare)
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A new purely growing instability in a strongly magnetized nonuniform pair plasma
- 2007
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Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 367:1-2, s. 120-122
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that a strongly magnetized nonuniform electron–positron (hereafter referred to as e–p or pair) plasma is unstable against low-frequency (in comparison with the electron gyrofrequency) electrostatic oscillations. For this purpose, a dispersion relation is derived by using the Poisson equation as well as the electron and positron continuity equations with the guiding center drifts for the electron and positron fluids. The dispersion relation admits a purely growing instability in the presence of the equilibrium density and magnetic field inhomogeneities. Physically, instability arises because of the inhomogeneous magnetic field induced differential electron and positron density fluctuations, which do not keep in phase with the electrostatic potential arising from the charge separation in our nonuniform pair plasmas.
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| 2. |
- Shukla, Nitin, et al.
(författare)
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Magnetization of a quantum plasma by photons
- 2010
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Ingår i: PHYSICS LETTERS A. - : Elsevier Science B.V., Amsterdam.. - 0375-9601 .- 1873-2429. ; 374:15-16, s. 1749-1750
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that the ponderomotive force of large-amplitude electromagnetic waves (photons), which includes the electron spin current and exchange potential contributions in a quantum plasma, can generate magnetic fields. The present result can account for the magnetic fields in dense compact astrophysical objects and in the next generation laser-solid density plasma interaction experiments.
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| 3. |
- Shukla, Nitin, et al.
(författare)
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Nonlinear generation of zonal flows by ion-acoustic waves in a uniform magnetoplasma
- 2010
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Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 374:4, s. 592-594
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that large-scale zonal flows (ZFs) can be excited by Reynolds stress of nonlinearly interacting random phase ion-acoustic waves (EIAWs) in a uniform magnetoplasma. Since ZFs are associated with poloidal sheared flows, they can tear apart short scale EIAW turbulence eddies, and hence contribute to the reduction of the cross-field turbulent transport in a magnetized plasma. (C) 2009 Elsevier B.V. All rights reserved.
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| 4. |
- Abdelsalam, UM, et al.
(författare)
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Ion-acoustic solitary waves in a dense pair-ion plasma containing degenerate electrons and positrons
- 2008
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Ingår i: Physics Letters A. - Amsterdam : Elsevier. - 0375-9601 .- 1873-2429. ; 372:22, s. 4057-4061
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Tidskriftsartikel (refereegranskat)abstract
- Fully nonlinear propagation of ion-acoustic solitary waves in a collisionless dense/quantum electron-positron-ion plasma is investigated. The electrons and positrons are assumed to follow the Thomas-Fermi density distribution and the ions are described by the hydrodynamic equations. An energy balance-like equation involving a Sagdeev-type pseudo-potential is derived. Finite amplitude solutions are obtained numerically and their characteristics are discussed. The small-but finite-amplitude limit is also considered and an exact analytical solution is obtained. The present studies might be helpful to understand the excitation of nonlinear ion-acoustic solitary waves in a degenerate plasma such as in superdense white dwarfs.
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| 5. |
- Abdelsalam, UM, et al.
(författare)
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Localized electrostatic excitations in a Thomas-Fermi plasma containing degenerate electrons
- 2008
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Ingår i: Physics of Plasmas. - Melville : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 15:5
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Tidskriftsartikel (refereegranskat)abstract
- By using the Thomas-Fermi electron density distribution for quantum degenerate electrons, the hydrodynamic equations for ions, and the Poisson equation, planar and nonplanar ion-acoustic solitary waves in an unmagnetized collisionless plasma are investigated. The reductive perturbation method is used to derive cylindrical and spherical Korteweg-de Vries equations. Numerical solutions of the latter are presented. The present results can be useful in understanding the features of small but finite amplitude localized ion-acoustic solitary pulses in a degenerate plasma.
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| 6. |
- Ali, S, et al.
(författare)
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Dispersion properties of compressional electromagnetic waves in quantum dusty magnetoplasmas
- 2006
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Ingår i: Physics of Plasmas. - Melville : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 13:5
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Tidskriftsartikel (refereegranskat)abstract
- A new dispersion relation for low-frequency compressional electromagnetic waves is derived by employing quantum magnetohydrodynamic model and Maxwell equations in cold quantum dusty magnetoplasmas. The latter is composed of inertialess electrons, mobile ions, and immobile charged dust particulates. The dispersion relation for the low-frequency compressional electromagnetic modes is further analyzed for the waves propagating parallel, perpendicular, and oblique to the external magnetic field direction. It is found theoretically and numerically that the quantum parameter alpha(q)=(n(i0)/n(e0))h(2)/(4m(e)m(i)) affects the real angular frequencies and the phase speeds of the compressional electromagnetic modes. Here, n(i0) (n(e0)) is the equilibrium number density of the ions (electrons), m(e) (m(i)) is the electron (ion) mass, and h is the Plank constant divided by 2 pi.
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| 7. |
- Ali, S, et al.
(författare)
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Wake potential with mobile positive/negative ions in multicomponent dusty plasmas
- 2008
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Ingår i: Physics Letters A. - Amsterdam : Elsevier. - 0375-9601 .- 1873-2429. ; 372:44, s. 6650-6652
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Tidskriftsartikel (refereegranskat)abstract
- We employ the test charge approach to calculate the electrostatic potential for a test charge in a multicomponent dusty plasma, whose constituents are the Boltzmann distributed electrons, mobile positive and negative ions, and immobile positive/negative charged dust particles. By using the modified dielectric constant of the dust-ion-acoustic (DIA) waves, the Debye screening and wake potentials are obtained. It is found that the presence of mobile negative ions significantly modify the DIA speed and the wake potential. The present results are relevant to polar mesosphere and microelectronic in the context of charged particle attraction and repulsion.
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| 8. |
- Ali, Shahid, 1975-
(författare)
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Waves and instabilities in quantum plasmas
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The study of waves and instabilities in quantum plasmas is of fundamental importance for understanding collective interactions in superdense astrophysical objects, in high intense laser-plasma/solid-matter interactions, in microelectronic devices and metallic nanostructures. In dense quantum plasmas, there are new pressure laws associated with the Fermi-Dirac distribution functions and new quantum forces associated with the quantum Bohm potential and the Bohr magnetization involving electron ½ spin. These forces significantly alter the collective behavior of dense quantum plasmas. This thesis contains six papers, considering several novel collective modes and instabilities at quantum scales. In Paper I, we have used the quantum hydrodynamical (QHD) model for studying the one-dimensional dust-acoustic (DA) waves incorporating the Fermi pressure law and the quantum Bohm potential. The latter modifies the DA wave dispersion relation in a collisional plasma. In Paper II, we have calculated the electrostatic potential of a test charge in an unmagnetized electron-ion quantum plasma. It is found that the Debye-Hückel and oscillatory wake potentials strongly depend upon the Fermi energy at quantum scales. The results can be of interest for explaining the charged particle attraction and repulsion in degenerate quantum plasmas, such as those in semiconductor and microelectronic devices. Paper III presents the parametric study of nonlinear electrostatic waves in two-dimensional collisionless quantum dusty plasmas. A reductive perturbation method has been employed to the QHD equations together with the Poisson equation, obtaining the cylindrical Kadomtsev-Petviashvili (CKP) equations and their stationary localized solutions. We have numerically examined the quantum mechanical and geometrical effects on the profiles of nonplanar quantum dust-ion-acoustic (DIA) and DA solitary waves. The role of static as well as mobile (negatively or positively charged) dust particles on the low-frequency electrostatic waves has also been highlighted for metallic nanostructures. Paper IV introduces the nonlinear properties of the ion-sound waves in a dense electron-ion Fermi magnetoplasma. The computational analysis of the nonlinear system reveals that the Sagdeev-like potential and the ion-sound density excitations are significantly affected by the wave direction cosine and the Mach number at quantum scales. Paper V considers the nonlinear interactions of electrostatic upper-hybrid (UH), ion-cyclotron (IC), lower-hybrid (LH), and Alfvén waves in a quantum magnetoplasma. The nonlinear dispersion relations have been analyzed analytically to obtain the growth rates for both the decay and modulational instabilities involving the dispersive IC, LH, and Alfvén waves. In Paper VI, we have identified a new drift-like dissipative instability in a collisional quantum plasma. The modified unstable drift-like mode can cause cross-field anomalous ion-diffusion at quantum scales.
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| 9. |
- Bingham, R, et al.
(författare)
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Coronal heating by dissipating current sheets
- 2004
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Ingår i: Physica scripta. T. - Bristol : Institute of Physics (IOP). - 0281-1847. ; T107, s. 247-249
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that the lower-hybrid turbulence produced by the lower-hybrid-drift wave instability at current sheets can heat electrons and ions in the solar corona. The waves heat the plasma particles by collisionless Landau damping. The waves resonate with electrons moving in the direction of the magnetic field, while they resonate with ions moving in the perpendicular direction.
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| 10. |
- Bingham, Robert, et al.
(författare)
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Solar coronal heating by plasma waves
- 2010
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Ingår i: Journal of Plasma Physics. - : Cambridge university. - 0022-3778 .- 1469-7807. ; 76:2, s. 135-158
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Tidskriftsartikel (refereegranskat)abstract
- The solar coronal plasma is maintained at temperatures of millions of degrees, much hotter than the photosphere, which is at a temperature of just 6000 K. In this paper, the plasma particle heating based on the kinetic theory of wave–particle interactions involving kinetic Alfvén waves and lower-hybrid drift modes is presented. The solar coronal plasma is collisionless and therefore the heating must rely on turbulent wave heating models, such as lower-hybrid drift models at reconnection sites or the kinetic Alfvén waves. These turbulent wave modes are created by a variety of instabilities driven from below. The transition region at altitudes of about 2000 km is an important boundary chromosphere, since it separates the collision-dominated photosphere/chromosphere and the collisionless corona. The collisionless plasma of the corona is ideal for supporting kinetic wave–plasma interactions. Wave–particle interactions lead to anisotropic non-Maxwellian plasma distribution functions, which may be investigated by using spectral analysis procedures being developed at the present time.
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