| 1. |
- Abdelsalam, UM, et al.
(författare)
-
Localized electrostatic excitations in a Thomas-Fermi plasma containing degenerate electrons
- 2008
-
Ingår i: Physics of Plasmas. - Melville : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 15:5
-
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.
|
|
| 2. |
- Ali, S, et al.
(författare)
-
Dispersion properties of compressional electromagnetic waves in quantum dusty magnetoplasmas
- 2006
-
Ingår i: Physics of Plasmas. - Melville : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 13:5
-
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.
|
|
| 3. |
- Eliasson, Bengt, et al.
(författare)
-
Dynamics of nonlinearly interacting magnetic electron drift vortex modes in a nonuniform plasma
- 2009
-
Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 16:4, s. 042306-
-
Tidskriftsartikel (refereegranskat)abstract
- A simulation study of dynamical evolution of nonlinearly interacting two-dimensional magnetic electron drift vortex (MEDV) modes in a nonuniform plasma is presented. Depending on the equilibrium density and temperature gradients, the system can either be stable or unstable. The unstable system reveals spontaneous generation of magnetic fields from noise level, and large-scale magnetic field structures are formed. When the system is linearly stable, one encounters MEDV mode turbulence in which there is a competition between zonons (zonal flows) and streamers. For large MEDV mode amplitudes, one encounters the formation of localized and small-scale magnetic vortices and vortex pairs with scale sizes of the order of the electron skin depth. The MEDV turbulence exhibits nonuniversal (non-Kolmogorov-type) spectra for different sets of plasma parameters. The relevance of this work to laboratory and cosmic plasmas is briefly mentioned. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3103785]
|
|
| 4. |
- Eliasson, Bengt, et al.
(författare)
-
Numerical and theoretical study of Bernstein modes in a magnetized quantum plasma
- 2008
-
Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 15, s. 102102-
-
Tidskriftsartikel (refereegranskat)abstract
- A numerical and theoretical study is presented for the propagation of electron Bernstein modes in a magnetized quantum plasma. The dispersion relation for electrostatic waves is derived, using a semiclassical Vlasov model for Fermi–Dirac distributed electrons. The dispersion relation is checked numerically with direct Vlasov simulations, where the wave energy is concentrated to the Bernstein modes as well as to the zero-frequency convective mode. Dispersion relations in the long wavelength limit are derived, including the upper hybrid dispersion relation for a degenerate quantum plasma.
|
|
| 5. |
- Haas, F, et al.
(författare)
-
Nonlinear stationary solutions of the Wigner and Wigner-Poisson equations
- 2008
-
Ingår i: Physics of Plasmas. - Melville : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 15:11
-
Tidskriftsartikel (refereegranskat)abstract
- Exact nonlinear stationary solutions of the one-dimensional Wigner and Wigner-Poisson equations in the terms of the Wigner functions that depend not only on the energy but also on position are presented. In this way, the Bernstein-Greene-Kruskal modes of the classical plasma are adapted for the quantum formalism in the phase space. The solutions are constructed for the case of a quartic oscillator potential, as well as for the self-consistent Wigner-Poisson case. Conditions for well-behaved physically meaningful equilibrium Wigner functions are discussed.
|
|
| 6. |
- Haas, F, et al.
(författare)
-
Nonlinear structure in a current-carrying collisional dusty plasma
- 2008
-
Ingår i: Physics of Plasmas. - Melville : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 15:9
-
Tidskriftsartikel (refereegranskat)abstract
- A perpendicular ion drift is proposed as a possible mechanism for the generation of magnetic field structures in a highly collisional dusty plasma. The basic dissipation mechanism is assumed to be the dust-neutral momentum exchange, so that plasmas with a small ionization fraction are natural candidates for experiments. The model reduces to a nonlinear partial differential equation for the vector potential. The conditions for linear instability are presented. Possible stationary states are periodic arrangements for the magnetic field, described by a Lienard equation. The fully depleted (ion-dust) case is also considered in detail. Applications of the present work to magnetic field structures in planetary rings, comets, and low-temperature dusty plasma experiments are discussed. A necessary condition for the validity of the model is a sufficiently slow time scale of the generated magnetic fields in dusty plasmas.
|
|
| 7. |
- Mamun, A. A., et al.
(författare)
-
Arbitrary amplitude dust ion-acoustic shock waves in a dusty plasma with positive and negative ions
- 2009
-
Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 16, s. 114503-
-
Tidskriftsartikel (refereegranskat)abstract
- Arbitraryamplitude dust ion-acoustic shock waves in a multi-ion dusty plasma(composed of electrons, light positive ions, heavy negative ions, andstationary massive dust grains) has been studied. For this purpose,the coupled Poisson and dust-charging equations, which accounts for thefluctuation of charges on static dust, have been numerically solved.The large amplitude shocks are associated with a sudden decreasein the electrostatic potential and of the dust grain charge.It is found that in the lower speed limit smallamplitude shocks are formed, while in the larger speed limitlarge amplitude shocks are formed. It is anticipated that theprofiles and amplitudes of the DIA shocks predicted here willbe observed in forthcoming laboratory and space experiments.
|
|
| 8. |
- Marklund, Mattias, et al.
(författare)
-
Quantum electrodynamical effects in dusty plasmas
- 2005
-
Ingår i: Physics of Plasmas. - Melville : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 12:7
-
Tidskriftsartikel (refereegranskat)abstract
- A new nonlinear electromagnetic wave mode in a magnetized dusty plasma is predicted. Its existence depends on the interaction of an intense circularly polarized electromagnetic wave with a dusty plasma, where quantum electrodynamical photon-photon scattering is taken into account. Specifically, we consider a dusty electron-positron-ion plasma and show that the propagation of the new mode is admitted. It could be of significance for the physics of supernova remnants and in neutron star formation.
|
|
| 9. |
- Misra, AP, et al.
(författare)
-
Modulational instability of magnetosonic waves in a spin 1/2 quantum plasma
- 2008
-
Ingår i: Physics of Plasmas. - Melville : American Institute of Physics (AIP). - 1070-664X .- 1089-7674. ; 15:5
-
Tidskriftsartikel (refereegranskat)abstract
- The modulational instability (MI) of magnetosonic waves (MSWs) is analyzed, by using a two-fluid quantum magnetohydrodynamic model that includes the effects of the electron-1/2 spin and the plasma resistivity. The envelope modulation is then studied by deriving the corresponding nonlinear Schrodinger equation from the governing equations. The plasma resistivity is shown to play a dissipative role for the onset of MI. In the absence of resistivity, the microscopic spin properties of electrons can also lead to MI. In such a situation, the dominant spin contribution corresponds to a dense quantum plasma with the particle number density, n(0)greater than or similar to 10(28) m(-3). Also, in such a dissipative (absorbing) medium, where the group velocity vector is usually complex for real values of the wave vector, the role of the real group velocity in the propagation of one-dimensional MSW packets in a homogeneous absorbing medium is reported. The effects of quantum spin on the stability/instability conditions of the magnetosonic envelope are obtained and examined numerically. From the nonlinear dispersion relation of the modulated wave packet it is found that the effect of the spin (plasma resistivity) is to decrease (increase) the instability growth rate provided the normalized Zeeman energy does not exceed a critical value. The theoretical results may have relevance to astrophysical (e.g., magnetars) as well as to ultracold laboratory plasmas (e.g., Rydberg plasmas).
|
|
| 10. |
- Misra, Amar Prasad, et al.
(författare)
-
Modulational instability and nonlinear evolution of two-dimensional electrostatic wave packets in ultra-relativistic degenerate dense plasmas
- 2011
-
Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 18:4
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the nonlinear propagation of electrostatic wave packets in an ultra-relativistic (UR) degenerate dense electron-ion plasma, whose dynamics is governed by the nonlocal two-dimensional nonlinear Schrodinger-like equations. The coupled set of equations is then used to study the modulational instability (MI) of a uniform wave train to an infinitesimal perturbation of multidimensional form. The condition for the MI is obtained, and it is shown that the nondimensional parameter, beta proportional to lambda(C)n(0)(1/3) (where lambda(C) is the reduced Compton wavelength and n(0) is the particle number density) associated with the UR pressure of degenerate electrons, shifts the stable (unstable) regions at n(0) similar to 10(30)cm(-3) to unstable (stable) ones at higher densities, i.e., n(0) greater than or similar to 7 x 10(33). It is also found that the higher the values of n(0), the lower is the growth rate of MI with cut-offs at lower wave numbers of modulation. Furthermore, the dynamical evolution of the wave packets is studied numerically. We show that either they disperse away or they blowup in a finite time, when the wave action is below or above the threshold. The results could be useful for understanding the properties of modulated wave packets and their multidimensional evolution in UR degenerate dense plasmas, such as those in the interior of white dwarfs and/or pre-Supernova stars.
|
|
