共查询到20条相似文献，搜索用时 35 毫秒
1.
The Rayleigh-Taylor instability of the plane interface separating two superposed, partiallyionized, viscous plasmas of different densities has been studied to include the effects of finite Larmor radius. The solution of the relevant linearized perturbation equations has been developed by the Normal mode technique, taking the prevalent magnetic field to be uniform and horizontal. The potentially unstable case of a dense fluid superimposed on a lighter one has been considered. It is found that neutral gas friction, viscosity as well as finite Larmor radius all have stabilizing influence.On leave of absence from Department of Mathematics, University of Jodhpur, India. 相似文献
2.
The instability in a horizontal layer of stratified compressible isotropic and anisotropic plasmas has been studied to include
simultaneously the effects of Coriolis forces and the finiteness of the ion Larmor radius. Using an integral approach, the
dispersion relation has been derived in both cases for plasmas having density stratified exponentially along the vertical.
The dispersion, relation has been solved numerically and it is found that both the FLR and Coriolis forces have stabilizing
influence on the instability in the isotropic plasmas. The same result is obtained for the case of anisotropic plasmas where
also the dispersion relation has been evaluated numerically. 相似文献
3.
The problem of Rayleigh-Taylor instability of superposed viscous magnetized fluids through porous medium is investigated in a partially-ionized medium. The fluid has ionized and neutralized particle components interacting with collisions. The effect of surface tension on R-T instability is also included in the present problem. The magnetohydrodynamic equations are modified for finite-Larmor radius corrections which is in the form of tensor. The equations of problem are linearized and using appropriate boundary condition, general dispersion relation is derived for two superposed fluids separated by horizontal boundary. The first part of the dispersion relation gives stable mode and condition is investigated using Hurwitz conditions. The second part of the dispersion relation shows that the growth rate of unstable system is reduced due to FLR corrections, viscosity, and collisional frequency of the neutrals. The role of surface tension on the system is also discussed. 相似文献
4.
The Rayleigh-Taylor instability of the plane interface separating the two partially-ionized superposed fluids through porous medium is analysed. The effect of variable horizontal magnetic field, surface tension and rotation along the vertical axis are also incorporated. The relevant linearized perturbation equations are taken and using normal mode analysis the general relation is obtained from which the dispersion relation for two superposed fluids of different densities is derived. It is found that the surface tension and horizontal magnetic field have the stabilizing effect on the R-T-instability. The condition of instability remains unaffected by the permeability of porous medium, presence of neutral particles in the fluids and rotation.It is concluded that the system is unstable only for those positive wave numbers which are less than certain critical value in case of an adverse density gradient. 相似文献
5.
The Kelvin-Helmholtz discontinuity in two superposed viscous conducting fluids has been investigated in the presence of a two-dimensional horizontal uniform magnetic field. The streaming motion is also assumed to be two-dimensional. The stability analysis has been carried out for two highly viscous fluids of uniform densities. It is found that the streaming motion has dual influence on the unstable system, destabilizing for low values of streaming velocity and stabilizing for high values of streaming velocity. The effect of viscosity is, however, found to be stabilizing as the growth rate of the unstable configuration decreases on increasing the viscosity. 相似文献
6.
This paper gives a generalised theory of hydromagnetic stability of the interface between two infinitely-conducting, compressible plasmas with the latter accelerated perpendicular to the interface and streaming parallel to the interface and subjected to a constant magnetic field parallel to the streaming direction. The method used is adapted from the one given by Plesset and Hsieh (1964) for the hydrodynamical case and the general dispersion relation is found to involve Whittaker's functions and their first derivatives. The familiar Rayleigh-Taylor and Kelvin-Helmholtz instability problems are recovered from the general dispersion relation in the appropriate special cases. 相似文献
7.
The self-gravitating instability of an infinitely extending axisymmetric cylinder of viscoelastic medium permeated with non uniform magnetic field and rotation is studied for both the strongly coupled plasma (SCP) and weakly coupled plasma (WCP). The non uniform magnetic field and rotation are considered to act along the axial direction of the cylinder. The normal mode method of perturbations is applied to obtain the dispersion relation. The condition for the onset of gravitational instability has been derived from the dispersion relation under both strongly and weakly coupling limits. It is found that the Jeans criterion for gravitational collapse gets modified due to the presence of shear and bulk viscosities for the SCP, however, the magnetic field and rotation whether uniform or non uniform has no effect on the Jeans criterion of an infinitely extending axisymmetric cylinder of a self-gravitating viscoelastic medium. 相似文献
8.
Bhimsen K. Shivamoggi 《Astrophysics and Space Science》1981,79(1):3-9
A study of the Rayleigh instability of a compressible plasma of density stratified in horizontal planes and subjected to a vertical magnetic field is made. The special case of a plane interface separating two superposed uniform plasmas of different densities and speeds of sound is treated as an example to illustrate the compressibility effects on the hydromagnetic Rayleigh instability. It is found that the hydromagneticcompressibility effects act toward reducing the growth rate in a hydrodynamically unstable situation. 相似文献
9.
P. D. Ariel 《Astrophysics and Space Science》1987,135(2):365-375
The Rayleigh-Taylor instability of two rotating superposed fluids in the presence of a vertical magnetic field has been investigated. It is shown thatn
2 is purely real, wheren is the growth rate of a perturbation. In the basis of this fact it is shown that a unique dispersion relation exists if the lighter fluid lies beneath the heavier one. However, if the heavier fluid lies beneath the lighter fluid, then no unique dispersion relation exists. The effect of rotation is to slow down the rate at which potentially unstable stratification departs from the equilibrium position. 相似文献
10.
Kelvin-Helmholtz instability of the interface separating two viscous rotating-conducting fluids has been studied in the presence of finite ion-Larmor radius (FLR) effects. Emloying the normal mode technique, the solutions have been obtained when the fluids are assumed to be permeated by a uniform horizontal magnetic field. For the case of two highly viscous fluids, the dispersion relation has been derived and solved numerically. It is found that the streaming velocity has a stabilizing influence on the potentially unstable arrangement of the fluids. The viscosity and FLR effects are also found to have a stabilizing influence while the Coriolis forces have a destabilizing influence on the system. 相似文献
11.
Properties of fully nonlinear ion-acoustic solitary waves in an unmagnetized and collisionless pair-ion (PI) plasma containing superthermal electrons obeying Cairns distribution have been analyzed. A linear biquadratic dispersion relation has been derived, which yields the fast (supersonic) and slow (subsonic) modes in a pair-ion-electron plasma with nonthermal electrons. For nonlinear analysis, Korteweg-de Vries equation is obtained using the reductive perturbation technique. It is found that in case of slow mode, both electrostatic hump and dip type structures are formed depending on the temperature difference between positively and negatively charged ions, whereas, only dip type solitary structures have been observed for fast mode. The present work may be employed to explore and to understand the formation of solitary structures in the space (especially, the Earth’s ionosphere where two distinct pair ion species (H ±) are present) and laboratory produced pair-ion plasmas with nonthermal electrons. 相似文献
12.
The effect of Hall currents have been studied on the instability of a stratified layer of a self-gravitating finitely conducting plasma of varying density. It is assumed that the plasma is permeated by a variable horizontal magnetic field stratified vertically. The stability analysis has been carried out for longitudinal mode of wave propagation. The solution has been obtained through integral equation approach. The dispersion relation has been derived and solved numerically. It is found that both the Hall currents and finite conductivity have a destabilizing influence on the growth rate of the unstable mode of disturbance. 相似文献
13.
In the relativistic case, the dispersion equation of longitudinal oscillations in unmagnetized, collisionless and isotropic plasmas of fast electron distribution is derived from the longitudinal dielectric constant of plasma. The equation is analytically solved, and the long-wavelength and short-wavelength dispersion relations are obtained. Because of the discontinuity of the analytical dispersion curve, the dimensionless dispersion equation of longitudinal oscillations is numerically calculated to obtain the full dispersion curve of longitudinal oscillations in relativistic plasmas of fast electron distribution. Further more, by fitting the numerical solution, a simple functional expression of the dispersion curve is given in favor of applications. Finally, in the extremely relativistic case, the dispersion relation of fast electron distribution is compared with that of Maxwell distribution. It is shown that the two kinds of dispersion relations have similar properties in a certain range of wave numbers. 相似文献
14.
The instability of a stratified layer of a self-gravitating plasma has been studied to include jointly the effects of viscosity, Coriolis forces and the finite Larmor radius (FLR). For a plasma permeated by a uniform horizontal magnetic field, the stability analysis has been carried out for a transverse mode of wave propagation. The solution has been obtained through variational methods for the case when the direction of axis of rotation is along the magnetic field. The analysis for the case when the direction of rotation is transverse to the magnetic field has also been considered and the solutions for this case have been obtained through integral approach. The dispersion relations have been derived in both the cases and solved numerically. It is found that both the viscous and FLR effects have a stabilizing influence on the growth rate of the unstable mode of disturbance. Coriolis forces are found to have stabilizing influence for small wave numbers and destabilizing for large wave numbers. 相似文献
15.
Vinod Kumar Nagendra Kumar Krishna M. Srivastava R. C. Mittal 《Astrophysics and Space Science》1993,199(2):323-331
The problem of gravitational instability of an infinite homogeneous self-gravitating medium carrying a uniform magnetic field in the presence of Hall effect has been investigated to include the effect due to rotation. The dispersion relation has been obtained. It has been found that the Jeans's criterion for the instability remains unaffected even when the effect due to rotation is considered in the presence of Hall effect carrying a uniform magnetic. 相似文献
16.
A complete dispersion relation for a whistler mode wave propagation in an anisotropic warm ion-electron magnetoplasma in the presence of parallel electric field using the dispersion relation for a circularly polarized wave has been derived. The dispersion relation includes the effect of anisotropy for the ion and electron velocity distribution functions. The growth rate of electron-ion cyclotron waves for different plasma parameters observed atL = 6.6R
E
has been computed and the results have been discussed in detail in the light of the observed features of VLF emissions and whistlers. The role of the combination of ion-cyclotron and whistler mode electromagnetic wave propagation along the magnetic field in an anisotropic Maxwellian weakly-ionized magnetoplasma has been studied. 相似文献
17.
P. D. Ariel 《Astrophysics and Space Science》1974,29(2):319-329
The hydromagnetic stability of an electrically conducting compressible plasma having variable density in the vertical direction
has been investigated taking into account the effects of Hallcurrents. The solution is shown to be characterized by a variational
principle. Based on the existence of variational principle, the dispersion relation has been obtained for the case of a plasma
having exponentially varying density with special reference to stellar atmosphere. It is found that both compressibility of
the medium and Hall-currents destabilize the configuration for the disturbances, for which it was stable otherwise. The Hall-currents
even suppress the mode of maximum instability for large magnitudes. 相似文献
18.
19.
Daniel Atnafu Chekole Gebretsadikan Woldmhret Bahta 《Journal of Astrophysics and Astronomy》2018,39(6):67
Magnetohydrodynamics waves and instabilities in rotating, self-gravitating, anisotropic and collision-less plasma were investigated. The general dispersion relation was obtained using standard mode analysis by constructing the linearized set of equations. The wave mode solutions and stability properties of the dispersion relations are discussed in the propagations transverse and parallel to the magnetic field. These special cases are discussed considering the axis of rotation to be in transverse and along the magnetic field. In the case of propagation transverse to the magnetic field with axis of rotation parallel to the magnetic field, we derived the dispersion relation modified by rotation and self-gravitation. In the case of propagation parallel to the magnetic field with axis of rotation perpendicular to the magnetic field, we obtained two separate modes affected by rotation and self-gravitation. This indicates that the Slow mode and fire hose instability are not affected by rotation. Numerical analysis was performed for oblique propagation to show the effect of rotation and self-gravitation. It is found that rotation has an effect of reducing the value of the phase speeds on the fast and Alfven wave modes, but self-gravitation affect only on the Slow modes, thereby reducing the phase speed compare to the ideal magneto hydrodynamic (MHD) case. 相似文献
20.
The magnetodynamic (in)stability of a conducting fluid cylinder subject to the capillarity and electromagnetic forces has been developed. The cylinder is pervaded by a uniform magnetic field but embedded in the Lundquist force-free varying field that allows for flowing a current surrounding the fluid. A general eigenvalue relation is derived based on a study of the equilibrium and perturbed states. The stability criterion is discussed analytically in general terms. The surface tension is destabilizing for small axisymmetric mode and stable for all others. The principle of the exchange of stability is allowed for the present problem due to the non-uniform behaviour of the force-free field. Each of the axial and transverse force-free fields separately exerts a stabilizing influence in the most dangerous mode but the combined contribution of them is strongly destabilizing. Whether the model is acted upon the electromagnetic force (with the Lundquist field) the stability restrictions or/and the capillarity force are identified.Several reported works can be recovered as limiting cases with appropriate simplifications. 相似文献