共查询到20条相似文献，搜索用时 124 毫秒
1.
The effect of rotation on the self-gravitational instability of an infinite homogeneous magnetized Hall plasma is considered with the inclusion of finite Larmor radius corrections and the effect of suspended particles. A general dispersion relation is obtained from the linearized set of equations. The particular cases of the effect of rotation along and perpendicular to the direction of the magnetic field are considered. The effects of Hall current, finite Larmor radius, and suspended particles on the waves propagated parallel and perpendicular to the uniform magnetic field are investigated along with the uniform rotation of the medium. It is found that in the presence of suspended particles, magnetic field, Hall current, rotation and finite Larmor radius, the Jeans criterion determines the condition of gravitational instability of a gas-particle medium. 相似文献
2.
Thermosolutal-convective instability of a composite plasma in a stellar atmosphere is considered. The effect of a variable horizontal magnetic field and the simultaneous effect of a uniform rotation and a variable horizontal magnetic field have been considered on the thermosolutal-convective instability. We have derived the sufficient conditions for the existence of monotonic instability. It is found that the criteria for monotonic instability hold good in the presence of a variable horizontal magnetic field as well as in the presence of a uniform rotation and a variable horizontal magnetic field. 相似文献
3.
On thermal-convective instability in a stellar atmosphere with finite Larmor radius and Hall effects
The thermal-convective instability of a stellar atmosphere is considered to include rotation, finite Larmor radius and Hall effects in the presence of a uniform vertical magnetic field. The criterion for monotonic instability is found to be the same even if the above effects are included. 相似文献
4.
R. C. Sharma 《Astrophysics and Space Science》1974,29(1):L1-L4
The gravitational instability of an infinite homogeneous self-gravitating rotating plasma in the presence of a uniform vertical magnetic field has been studied to include the FLR effects. It has been found that the Jeans' criterion of instability remains unaffected even if rotation and FLR effects are included. The effect of rotation is to decrease the Larmor radius by an amount-depending upon the wavenumber of perturbation. The particular cases of the effect of FLR and rotation on the waves propagated along and perpendicular to the magnetic field have been discussed. 相似文献
5.
Thermosolutal-convective instability of a stellar atmosphere is considered. The criteria for monotonic instability are derived. The effects of a variable horizontal magnetic field and the simultaneous presence of a uniform rotation and a uniform horizontal magnetic field have been considered on the thermosolutal-convective instability. The criteria derived for monotonic instability are found to hold good in the presence of a variable horizontal magnetic field as well as in the presence of a uniform rotation and a uniform horizontal magnetic field. 相似文献
6.
Thermosolutal-convective instability of a stellar atmosphere in the presence of a stable solute gradient 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 criteria derived for monotonic instability are found to hold true in the presence of FLR and Hall effects. 相似文献
7.
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
8.
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
9.
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
10.
We investigate the stability of the Hall‐MHD system and determine its importance for neutron stars at their birth, when they still consist of differentially rotating plasma permeated by extremely strong magnetic fields. We solve the linearised HallMHD equations in a spherical shell threaded by a homogeneous magnetic field. With the fluid/flow coupling and the Hall effect included, the magnetorotational instability and the Hall effect are both acting together. Results differ for magnetic fields aligned with the rotation axis and anti‐parallel magnetic fields. For a positive alignment of the magnetic field the instability grows on a rotational time‐scale for any sufficiently large magnetic Reynolds number. Even the magnetic fields which are stable against the MRI due to the magnetic diffusion are now susceptible to the shear‐Hall instability. In contrast, the negative alignment places strong restrictions on the growth and the magnitude of the fields, hindering the effectiveness of the Hall‐MRI. While non‐axisymmetric modes of the MRI can be suppressed by strong enough rotation, there is no such restriction when the Hall effect is present. The implications for the magnitude and the topology of the magnetic field of a young neutron star may be significant (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
R. P. Prajapati R. K. Pensia S. Kaothekar R. K. Chhajlani 《Astrophysics and Space Science》2010,327(1):139-154
The effects of arbitrary radiative heat-loss functions and Hall current on the self-gravitational instability of a homogeneous,
viscous, rotating plasma has been investigated incorporating the effects of finite electrical resistivity, finite electron
inertia and thermal conductivity. A general dispersion relation is obtained using the normal mode analysis with the help of
relevant linearized perturbation equations of the problem, and a modified Jeans criterion of instability is obtained. The
conditions of modified Jeans instabilities and stabilities are discussed in the different cases of our interest. We find that
the presence of arbitrary radiative heat-loss functions and thermal conductivity modifies the fundamental Jeans criterion
of gravitational instability into a radiative instability criterion. The Hall parameter affects only the longitudinal mode
of propagation and it has no effect on the transverse mode of propagation. For longitudinal propagation, it is found that
the condition of radiative instability is independent of the magnetic field, Hall parameter, finite electron inertia, finite
electrical resistivity, viscosity and rotation; but for the transverse mode of propagation it depends on the finite electrical
resistivity, the strength of the magnetic field, and it is independent of rotation, electron inertia and viscosity. From the
curves we find that the presence of thermal conductivity, finite electrical resistivity and density-dependent heat-loss function
has a destabilizing influence, while viscosity and magnetic field have a stabilizing effect on the growth rate of an instability.
The effect of arbitrary heat-loss functions is also studied on the growth rate of a radiative instability. 相似文献
12.
A. A. Abdullah 《Astrophysics and Space Science》1993,204(2):289-295
The problem of gravitational instability of an infinite homogenous fluid has been considered in the presence of a non-vertical magnetic field. A non-linear relation between the magnetic field and the magnetic induction proposed by P.H. Roberts (1981) in the context of neutron stars has been used. The dispersion relations have been obtained. It has been found that Jeans's criterion for instability is unaffected by this non-linear relationship even if the effect due to rotation is considered in the presence of a non-vertical magnetic field. 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.
K. C. Sharma 《Astrophysics and Space Science》1983,94(2):419-424
The gravitational instability of an infinite homogeneous self-gravitating and finitely conducting, rotating gas-particle medium, in the presence of finite Larmor radius, Hall currents and suspended particles effects is considered. The particular cases of the effects of rotation, finite conductivity, finite Larmor radius, Hall currents, and suspended particles on the waves propagated along and perpendicular to magnetic field have been discussed. It is found that Jeans's criterion remains unchanged in the presence of rotation, finite conductivity, finite Larmor radius, Hall currents, and suspended particles. 相似文献
15.
The gravitational instability of an infinite homogenous rotating plasma through a porous medium in the presence of a uniform magnetic field with finite electrical and thermal conductivities has been studied. With the help of relevant linearized perturbation equations of the problem, a general dispersion relation is obtained, which is further reduced for the special cases of rotation, parallel and perpendicular to the megnetic field acting in the vertical direction. Longitudinal and transverse modes of propagation are discussed separately. It is found that the joint effect of various parameters is simply to modify the Jeans's condition of instability. The effect of finite electrical conductivity is to remove the effect of magnetic field where as the effect of thermal conductivity is to replace the adiabatic velocity of sound by the isothermal one. Rotation has its effect only along the magnetic field in the transverse mode of propagation for an inviscid plasma, thereby stabilizing the system. Porosity reduces the effect of both, the magnetic field and the rotation, in the transverse mode of propagation in both the cases of rotation. The effect of viscosity is to remove the rotational effects parallel to the magnetic field in the transverse mode of propagation. 相似文献
16.
Thermosolutal-convective instability of a stellar atmosphere is considered in the presence of suspended particles. The criteria for monotonic instability are derived which are found to hold good in the presence of uniform rotation and uniform magnetic field, separately, on the thermosolutal-convective instability in the presence of suspended particles. 相似文献
17.
The thermosolutal-convective instability of a stellar atomsphere is studied in the presence of suspended particles. The criteria
for monotonic instability are derived and are found to hold good also in the presence of uniform rotation and uniform magnetic
field on the thermosolutal-convective instability. The thermosolutal-convective instability of a stellar atmosphere is also
studied in the presence of suspended particles and radiative transfer effects and the criteria for monotonic instability are
obtained in terms of source function. 相似文献
18.
The gravitational instability of an infinite homogeneous finitely conducting viscid fluid through porous medium is studied in the presence of a uniform vertical magnetic field and finite ion Larmor radius (FLR) effects. The medium is considered uniformly rotating along and perpendicular to the direction of the prevalent magnetic field. A general dispersion relation is obtained from the relevant linearized perturbation equations of the problem. Furthermore, the wave propagation along and perpendicular to the direction of existing magnetic field has been discussed for each direction of the rotation. It is found that the simultaneous presence of viscosity finite conductivity, rotation, medium porosity, and FLR corrections does not essentially change the Jeans's instability condition. The stabilizing influence of FLR in the case of transverse propagation is reasserted for a non-rotating and inviscid porous medium. It is shown that the finite conductivity has destabilizing influence on the transverse wave propagation whereas for longitudinal propagation finite conductivity does not affect the Jean's criterion. 相似文献
19.
The problem of self-gravitational instability of an infinite, homogeneous stratified gaseous medium with finite thermal conductivity and infinite electrical conductivity, in the presence of non-uniform rotation and magnetic field in the Chandrasekhar’s frame of reference, is studied. It is found that the magnetic field, whether uniform or non-uniform, has no effect on the Jeans’ criterion for gravitational instability and remains essentially unaffected. However, the thermal conductivity has the usual stabilizing effect on the criterion that the adiabatic sound velocity occurring in the Jeans criterion is replaced by the isothermal sound velocity. Thus, the present analysis extends the results of Chandrasekhar for the case of heat conducting medium and for non-uniform rotation and magnetic field. 相似文献
20.
Nonlinear analysis for Kelvin-Helmholtz instability of an incompressible, inviscid, rotating fluid with infinite conductivity in the presence of gravity and surface tension has been discussed. The unperturbed magnetic field on two sides of the interface is taken to be uniform. The nonlinear Schrödinger equation for the time variation of amplitude of small perturbations with wave number around the neutral stability is derived. It is found that stability of a magnetised K-H rotating configuration depends on the density ratio, surface tension, and discontinuity of velocity and magnetic field. The effect of an aligned magnetic field and rotation on the non-linear instability of a rotating conducting plasma has been discussed in certain important limiting cases. 相似文献