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1.
Instability in a horizontal layer of a stratified rotating self-gravitating plasma is studied to include simultaneously the effects of Hall currents and the finiteness of the ion Larmor radius. Proper solutions have been obtained through the variational methods for a semi-infinite plasma in which the density has an exponential gradient along the vertical. The dispersion relation obtained has been solved numerically and it is found that the growth rate of the unstable perturbations decreases with both coriolis forces and gyroviscous effects. The influence of the effects of gyroviscosity as well as of Coriolis forces is consequently stabilizing. Hall currents are found to have a destabilizing influence as the growth rate is found to increase with this effect. 相似文献
2.
Instability of a horizontal rotating layer of a self-gravitating electrically conducting fluid has been studied to simultaneously, include the effects of Hall currents and magnetic resistivity. The prevailing magnetic field is uniform and acts along the vertical direction along which the fluid has a one-dimensional density gradient. The solution has been obtained through the variational methods. The dispersion relation obtained has been solved numerically and it is found that Hall currents as well as magnetic resistivity have a destabilizing influence. Coriolis forces, however, have a stabilizing influence. 相似文献
3.
The Rayleigh-Taylor instability in a rotating plasma of variable density has been investigated to include simultaneously the effects of viscosity and the finiteness of the ion Larmor radius. It is shown that, for a plasma in which the density is stratified along the vertical, the solution is characterized by a variational principle. Making use of this, proper solutions have been otained for a semiinfinite plasma in which the density varies exponentially. The dispersion relation has been solved numerically and it is found that the influence of the effects of both FLR and viscosity is stabilizing. The Coriolis forces are found to have a dual role, stabilizing for small wave numbers and destabilizing for large wave numbers. The range of the small wave numbers, over which the Coriolis forces have a stabilizing influence, is found to increase with Coriolis forces. 相似文献
4.
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
5.
The effect of Hall currents and collision with neutrals on the instability of a horizontal layer of a self-gravitating partially-ionized plasma of varying density have been studied. It is assumed that the plasma is permeated by a variable horizontal magnetic field stratified vertically. A variational principle is shown to characterize the problem. By making use of the existence of the variational principle, proper solutions have been obtained for a semi-infinite plasma in which density has a one-dimensional (exponential) vertical stratification. The dispersion relation has been derived and solved numerically. It is found that the collisions with neutrals have a stabilizing influence while Hall currents have a destabilizing influence. 相似文献
6.
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
7.
Instability of a stratified layer of a partially-ionized plasma has been investigated in the simultaneous presence of the effects of Hall currents, magnetic resistivity, finite Larmor radius (FLR), and viscosity. The ambient magnetic field is assumed to be uniform and acting along the vertical direction. The solution is shown to be characterized by a variational principle, based on it the solution has been obtained for a plasma in which the density is stratified exponentially along the vertical. It is found that the viscosity, friction with neutrals, and FLR have all stabilizing influence on the growth rate of the unstable mode of disturbance. Magnetic resistivity and Hall currents are, however, found to have a destabilizing influence. 相似文献
8.
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
9.
The dynamic stability of a partially ionized, compressible Hall plasma of finite electrical conductivity has been investigated when the plasma is immersed in a uniform, horizontal magnetic field. Based on the variational principle, which is shown to characterize the problem, the solution has been obtained for a semi-infinite plasma confined between two planes and having an exponential density stratification along the vertical. It is found that the effect of neutral gas friction is stabilizing while magnetic resistivity, Hall currents and compressibility all have destabilizing influence.On leave of absence from Department of Mathematics, University of Jodhpur, Jodhpur, India. 相似文献
10.
The effects of Hall currents, finite conductivity, and collision with neutrals have been studied on the gravitational instability of a partially-ionized plasma. It is assumed that plasma is permeated by an oblique magnetic field. The dispersion relation has been obtained and numerical calculations have been performed to obtain the dependence of the growth rate of the gravitationally unstable mode on the various physical parameters involved. It is found that Jeans's criterion remains unchanged in the presence of Hall currents, finite conductivity, and collisions. The Hall currents, finite conductivity, and collisions have destabilizing influence on the unstable mode of wave propagation of a gravitational instability of partially-ionized plasma. 相似文献
11.
Thermosolutal instability of a rotating plasma with finite Larmor radius and Hall effects is studied. When the instability sets in as stationary convection, the Hall currents and the stable solute gradient are found to have destabilizing and stabilizing effects, respectively. For the case of no rotation, finite Larmor radius effects are always stabilizing forx greater than two and forx less than its critical valueN
cr. In the limit of vanishing Hall current, the stabilizing effect of Coriolis force is observed. The question of onset of instability as overstability is also discussed. 相似文献
12.
Thermal-convective instability of a hydromagnetic, composite, rotating, inviscid, and infinitely conducting plasma in a stellar atmosphere has been studied in the presence of Hall currents. It is found that the criterion for monotonic instability holds good in the presence of the effects due to rotation and Hall currents. 相似文献
13.
The thermosolutal instability of a partially-ionized plasma in porous medium is considered in the presence of a uniform vertical magnetic field to include the effects of collisions and Hall currents. For the case of stationary convection, Hall currents and medium permeability have destabilizing effects whereas the stable solute gradient has stabilizing effect on the system. The collisional effects disappear for stationary convection. The sufficient conditions for the existence of overstability are obtained. 相似文献
14.
In this paper an attempt has been made to determine the effect of Coriolis force on the shapes of Roche equipotential surfaces
of rotating stars and stars in binary systems. Equations of Roche equipotential surfaces have been obtained for rotating and
binary stars which take into account the effects of Coriolis force besides the centrifugal and gravitational forces. Shapes
of Roche equipotentials and values of Roche limits are obtained for different values of angular velocity of rotation for rotating
stars and for different values of mass ratios for the binary stars. The obtained results have been compared with the corresponding
results in which the effect of Coriolis force has not been considered. 相似文献
15.
The flow of an infinitely extending homogenous thermally conducting plasma permeated by a variable magnetic field is considered.
The combined effect of several physical parameters, namely Hall currents, finite conductivity, ion viscosity and thermal conductivity
on plasma instability is studied in the framework of Tsallis statistics. A new Jeans Criterion is derived, which depends explicitly
on the nonextensive parameter q. The standard values are obtained in the limiting case q=1. 相似文献
16.
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
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.
Thermosolutal-convective instability of a composite plasma in a stellar atmosphere is considered to include the effects, separately, due to finite Larmor radius (FLR) and Hall currents in the presence of a uniform horizontal magnetic field. The sufficient conditions for the existence of monotonic instability are derived and are found to hold good both in the presence, separately, of FLR and Hall current effects. 相似文献
19.
P. Donald Ariel 《Astrophysics and Space Science》1991,184(2):205-219
The Rayleigh-Taylor instability of a plasma layer in the presence of a horizontal magnetic field is investigated, taking into account the effects of Hall-currents and an arbitrarily large density gradient. It is shown for the general case that if the density decreases vertically upward, the system is thoroughly stable.For a plasma layer with exponentially varying density an approximate dispersion relation is obtained using the Galerkin's method. An analysis of the roots of the dispersion relation reveals that the Hall-currents loosen the stabilizing influence of the magnetic field and impart instability to the system. For sufficiently large values of the density gradient and the Hall currents the system is throughly destabilized for all perturbations. 相似文献
20.
S. Servidio V. Carbone L. Primavera P. Veltri K. Stasiewicz 《Planetary and Space Science》2007,55(15):2239-2243
By direct numerical simulations we investigate the nonlinear dynamics of a compressible Hall Magnetohydrodynamic (MHD) plasma. At small scales, where the Hall effect dominates, we found an increase of the compressibility of the system and the breakdown of the strong link between velocity and magnetic fields, typical of usual MHD. Moreover, we find that small-scale fluctuations are characterized by an anti-correlation between density and magnetic field intensity. These features characterize the excitation of a quasi-perpendicular magnetosonic turbulence that can be interpreted as the small-scale signature of the break-down of the MHD nonlinear energy cascade due to Hall effect. Fluctuations with the same properties, based on measurements by Cluster spacecraft in space plasma turbulence during different magnetopause crossings, have been recently observed. 相似文献