Anita Tiwari

Gravitational instability of rotating magnetized quantum anisotropic plasma

The present problem deals with the study of gravitational (Jeans) instability of magnetized, rotating, anisotropic plasmas considering quantum effects. The basic equations of the considered system are constructed using combined Chew–Goldberger–Low (CGL) fluid model and quantum magnetohydrodynamic (QMHD) fluid model. A dispersion relation is obtained using the normal mode technique which is discussed for transverse and longitudinal modes of propagation. It is found that a rotating quantum plasma influences the gravitational mode in transverse propagation but not in longitudinal propagation. The presence of rotation decreases the critical wavenumber and it has a stabilizing effect on the Jeans instability criterion of magnetized quantum plasma in transverse propagation. The firehose instability is unaffected due to the presence of uniform rotation and quantum corrections. We observe from the numerical analysis that region of instability and critical Jeans wavenumber are both decreased due to the presence of uniform rotation. The stabilizing influence of uniform rotation is observed for magnetized, rotating, anisotropic plasmas in the presence of quantum correction. In the case of a longitudinal mode of propagation we found the Jeans instability criterion is not affected by rotation. The quantum diffraction term has a stabilizing effect on the growth rate of the Jeans instability when the wave propagates along the direction of the magnetic field.

Jeans instability of a rotating self-gravitating viscoelastic fluid

The effect of rotation on the Jeans instability of a self-gravitating viscoelastic fluid has been investigated using generalized hydrodynamic fluid equations. A dispersion relation is obtained using the linearized perturbation equations and normal mode analysis which is discussed for directions of rotation parallel and perpendicular to the wave propagation in classical (hydrodynamic) as well as kinetic limits. The Jeans criterion of instability is also obtained and it is found that it is unaffected by the presence of rotation in both the classical hydrodynamic and kinetic limits. The effects of Mach number, shear viscosity, sound velocity and rotation on the growth rate of the Jeans instability are also discussed numerically and we found that the shear viscosity and rotation have stabilizing influences on the growth rates of instability in both perpendicular and parallel propagations with finite angular rotation frequency. The stability of the rotating viscoelastic fluid is discussed using the Routh-Hurwitz criterion.

Gravitational instability of an anisotropic and viscoelastic plasma

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.

Jeans Instability of Rotating Viscoelastic Fluid in the Presence of Magnetic Field

Abstract The Jeans instability of rotating viscoelastic fluid in the presence of uniform magnetic field is investigated using the generalised hydrodynamic (GH) model. A general dispersion relation is derived with the help of linearised perturbation equations using the normal mode analysis, which is further discussed for axis of rotation parallel and perpendicular to the direction of the magnetic field in both the weakly coupled (hydrodynamic) and strongly coupled (kinetic) limits. The onset criterion of Jeans instability for magnetised rotating viscoelastic fluid is obtained, which remains unaffected by the presence of rotation and magnetic field but depends upon viscoelastic effects. The graphical illustrations are depicted to see the influence of rotation, Mach number, shear and viscous effects, and sound speed on the growth rate of Jeans instability. It is found that all these parameters have stabilising influence on the growth rate of Jeans instability; hence, they are capable of collapsing to a self-gravitating, rotating, magnetised viscoelastic medium.

Quantum and FLR effects on the Rayleigh Taylor instability of stratified plasmas

The combined effects of quantum corrections and finite Larmor radius (FLR) have been investigated on the linear hydrodynamic Rayleigh-Taylor (RT) instability of an incompressible stratified plasma. The basic quantum magnetohydrodynamic equations incorporating quantum and FLR effects are constructed and linearized under the small amplitude approximation. The general dispersion relation is derived considering appropriate magnetic field and density profiles using the normal mode analysis. It is analyzed numerically to study the effects of quantum and FLR corrections on the growth rate of RT instability in the stratified hydrodynamic fluids. It is found that the cut-off wavenumber (kmax) and critical wavenumber (kc) determining the growth rate of RT instability are modified due to the presence of FLR corrections and quantum effects. The FLR and quantum corrections have a stabilizing effect on the growth rate of RT instability of a stratified plasma.

Effect of magnetic field on the Rayleigh Taylor instability of rotating and stratified plasma

In the present study the effect of magnetic field and rotation have been carried out on the Rayleigh Taylor instability of conducting and rotating plasma, which is assumed to be incompressible and confined between two rigid planes z = 0 and z = h. The dispersion relation of the problem is obtained by solving the basic MHD equations of the problem with the help normal mode technique and appropriate boundary conditions. The dispersion relation of the medium is analysed and the effect of magnetic field and angular velocity (rotation effect) have been examined on the growth rate of Rayleigh Taylor instability. It is found that the magnetic field and angular velocity (rotation effect) have stabilizing influence on the Rayleigh Taylor instability.

The Rayleigh Taylor instability of viscous fluids: Effect of finite Larmor radius and rotation

In the present paper the Rayleigh Taylor instability of two superposed conducting incompressible viscous fluids including the effect of finite Larmor radius and rotation has been investigated. The relevant MHD equations are solved by using normal mode method and a general dispersion relation is derived with the help of appropriate boundary conditions for the considered medium. The general dispersion relation of the medium is discussed for the stable and unstable configuration of Rayleigh Taylor instability. The growth rate of Rayleigh Taylor instability is analysed in the presence of finite Larmor radius and rotation and their influence are studied on the Rayleigh Taylor instability.

Effect of magnetic field on Rayleigh-Taylor instability of two superposed fluids

The effect of two dimensional magnetic field on the Rayleigh-Taylor (R-T) instability in an incompressible plasma is investigated to include simultaneously the effects of suspended particles and the porosity of the medium. The relevant linearized perturbation equations have been solved. The explicit expression of the linear growth rate is obtained in the presence of fixed boundary conditions. A stability criterion for the medium is derived and discussed the Rayleigh Taylor instabilities in different configurations. It is found that the basic Rayleigh-Taylor instability condition is modified by the presence of magnetic field, suspended particles and porosity of the medium. In case of an unstable R-T configuration, the magnetic field has a stabilizing effect on the system. It is also found that the growth rate of an unstable R-T mode decreases with increasing relaxation frequency thereby showing a stabilizing influence on the R-T configuration.