Gravitational instability of a composite and rotating plasma in the presence of a variable magnetic field through a porous medium (original) (raw)
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Astrophysics and Space Science
Abstraet. 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 effeet due to rotation is considered in the presence of Hall effect carrying a uniform magnetic.
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2009
The gravitational instability of infinitely extending homogeneous rotating plasma permeated by an oblique magnetic field is considered. The solution has been obtained through the normal mode technique and dispersion relation has been derived. It is shown that Jeans' criterion remains unchanged in the present problem. The dispersion relation obtained has been solved numerically and it has been found that the Coriolis forces and viscosity have a stabilizing influence while Hall current and magnetic resistivity have destabilizing influence on the growth rate of the unstable mode of disturbance.
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Beiträge aus der Plasmaphysik, 1985
The effect of uniform rotation on the self gravitational instability of an infinite homogeneous magnetised gas particle medium in the presence of suspended particles is investigated. The equations of the problem are linearized and the general dispersion relation for such system is obtained. The rotation is assumed along two different directions and separate dispersion relation for each case is obtained. The dispersion relation for propagation parallel and perpendicular to the uniform magnetic field along with rotation is derived. The effect of suspended particles on the different modes of propagation is investigated. It is found that in presence of suspended particles, magnetic field, rotation and viscosity, Jeans' criterion determines the condition of gravitational instability of gas‐particle medium.
2011
The combined influence of the effects of Hall currents, magnetic resistivity and viscosity has been studied on the gravitational instability of rotating homogeneous unbounded plasma in an oblique magnetic field. The solution has been obtained through the normal mode technique and the dispersion relation has been derived. It is shown that Jean’s criterion for gravitational instability remains unchanged. Solving numerically the dispersion relation for conditions prevailing in an astrophysical situation, it is found that the Coriolis force, viscosity, Hall currents and finite conductivity have stabilizing influence on the instability of the plasma of disturbance.
Gravitational instability of an anisotropic and viscoelastic plasma
Journal of Physics: Conference Series, 2017
The effect of pressure anisotropy is studied on the growth rate of gravitational instabilities in a viscoelastic medium. The problem is constructed with generalized hydrodynamic fluid model and Chew-Goldberger-Low fluid model for anisotropic pressure then a general dispersion relation for the viscoelastic medium is obtained using the normal mode analysis. The general dispersion relation is reduced for propagation along the magnetic field and propagation perpendicular to the magnetic field. These two modes are discussed for the classical or hydrodynamic and kinetic limits and conditions for jeans instability are obtained. We found that condition of Jeans instability is modified for viscoelastic medium under kinetic limit and depends on compressional viscoelastic mode. Numerical analysis for longitudinal mode for kinetic regime shows that the velocity of compressional viscoelastic mode has a stabilizing effect on the growth rate of Jeans instability. In the transverse mode, the Alfven velocity for kinetic regime has a stabilizing influence on the Jeans instability.
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The hydromagnetic instability of an infinitely long self-gravitating incompressible plasma cylinder
Applied Scientific Research, Section B, 1962
An iniinitely long self-gravitating incompressible plasma cylinder is considered. Inside the cylinder there is a uniform magnetic field B, parallel to its axis and outside there are magnetic fields Be parallel to the axis and Bo ro/r in the azimuthal direction. The surface currents arising due to the discontinuity in the magnetic fields across the surface are incorporated into the boundary conditions to derive a dispersion relation. The conclusions are: (a) The magnetic field configuration (Bi = Be = B0) has got a stabilizing effect for modesm = 0, 1 and 2, for modesm = 1 and 2 it keeps
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We consider the gravitational stability of a current carrying filamentary cloud in the presence of both axial and azimuthal magnetic fields using a simple analytic model. The azimuthal magnetic field is shown to give rise to a new contribution, dictated by Ampere's law, in the corresponding virial equation for magnetohydrodynamic equilibrium. From this we obtain a computationally inexpensive guidance on the gravitational stability of current carrying filamentary clouds. The approach not only provides a fresh insight into the essential physical mechanisms involved, but also demonstrates clearly that, for sufficiently large and yet astronomically realistic currents, the azimuthal magnetic field can cause filamentary clouds to undergo instability.