Thermal-convective instability of a composite rotating plasma in a stellar atmosphere with finite larmor radius

Thermal-convective instability of a hydromagnetic, composite, rotating, inviscid and infinitely conducting plasma in a stellar atmosphere has been studied in the presence of finite Larmor radius. It is found that the criterion for monotonic instability holds good in the presence of the effects due to rotation and finite Larmor radius.     

The gravitational instability of a rotating plasma in the presence of finite Larmor radius,Hall currents and suspended particles

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.     

Suspended particles and the gravitational instability of a rotating plasma

The gravitational instability of an infinite homogeneous self-gravitating and finitely conducting, rotating gas-particle medium, in the presence of a uniform vertical magnetic field, is studied to include finite Larmor radius and suspended particles effects. The particular cases of the effects of rotation, finite conductivity, finite Larmor radius and suspended particles on the waves propagated along and perpendicular to magnetic field have been discussed. Jeans's criterion determines the gravitational instability.     

Finite Larmor radius effect on thermal instability of a compressible rotating plasma

Thermal instability of a compressible rotating plasma in the presence of a uniform vertical magnetic field is studied to include the effects of finiteness of the ion-Larmor radius. When the instability sets in as stationary convection, the compressibility is found to have stabilizing effect. It is found that finite Larmor radius effects are always stabilizing forx greater than two and forx less than two they have a destabilizing influence in the presence of rotation. The stabilizing effect of coriolis force is observed and for the case of no rotation, finite Larmor radius effects are always stabilizing. The sufficient conditions for the nonexistence of overstability are investigated.     

Infrared spectra of carbonaceous chondrites and the composition of intertellar grains

Gravitational instability of an infinitely conducting hydromagnetic composite rotating plasma is considered to include simultaneously the finite Larmor radius effects and the frictional effects with neutrals. It is found that Jeans' criterion of instability holds good in the presence of rotation, finite Larmor radius and collisions with neutrals. The particular cases of the above effects on the waves propagated along and perpendicular to the magnetic field have been discussed. The effect of rotation is to decrease the Larmor radius by an amount depending upon the wave number of perturbation.     

On thermosolutal-convective instability in a stellar atmosphere

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.     

Effect of rotation and finite Larmor radius on magneto-gravitational instability of Hall plasma in the presence of suspended particles

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.     

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.     

Thermosolutal-convective instability of a composite plasma in a stellar atmosphere including the effects of finite larmor radius and Hall currents

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.     

Finite Larmor radius and Hall effects on thermosolutal instability of a plasma

The thermosolutal instability of a plasma with finite Larmor radius and Hall effects is studied. When the instability sets in as stationary convection, finite Larmor radius effects are always stabilizing forx(=k ² d ²/² greater than two and forx less than two, they have a stabilizing or destabilizing influence depending on the Larmor radius parameterN in the presence of Hall currents. On the other hand the Hall currents have both stabilizing and destabilizing effects on the thermosolutal instability forx less than two and forx greater than two depending on the Hall parameterM. The stable solute gradient is found to have a stabilizing effect on stationary convection. The case of overstability is also considered wherein the sufficient conditions for the non-existence of overstability are derived.     

Gravitational instability of a thermally-conducting plasma flowing through a porous medium in the presence of suspended particles

Magnetogravitational instability of a thermally-conducting, rotating plasma flowing through a porous medium with finite conductivity and finite Larmor radius in the presence of suspended particles has been investigated. The wave propagation has been considered for both parallel and perpendicular axes of rotation. Magnetic field is being taken in the vertical direction. A general dispersion relation has been derived through relevant linearized perturbation equations. It has been observed that the condition of instability is determined by the Jeans's criterion in its modifed form. Thermal conductivity replaces the adiabatic velocity of sound by the isothermal one. Rotation decreases the Larmor radius. Porosity decreases the Alfvén velocity. In case of a viscous medium the effects of FLR, rotation, and suspended particles are not observed in the Jeans's condition, for transverse propagation for rotational axis parallel to the magnetic field. The effects of rotation and FLR are decreased by the porosity and the suspended particles. Finite conductivity removes the Alfvén velocity from Jeans's condition.     

Finite larmor radius and hall effects on thermosolutal instability of a rotating plasma

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.     

Magneto-gravitational instability of a rotating and finitely-conducting fluid

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.     

The Rayleigh Taylor instability of superposed partially-ionized plasmas

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.     

Effect of finite Larmor radius on the gravitational instability of a conducting plasma layer of finite thickness surrounded by a non-conducting matter

The gravitational instability of an incompressible, infinitely conducting plasma layer of finite thickness surrounded a non-conducting matter has been investigated taking into account the effect of the finite Larmor radius. The magnetic field is assumed to be directed parallel to the interfaces. Only the perturbations transverse to the magnetic field are considered, though both the symmetric and asymmetric nature of the perturbations are taken into account. Using the normal mode technique, dispersion relations are obtained.It is found that the finite larmor radius has, in general, a stabilizing influence on the configuration. Even when the system is thoroughly unstable, it has been shown that there exists a critical value of the wave-number, such that the motion is stabilized for wave-numbers of perturbations exceeding this critical value.     

Effect of finite ion larmor radius on the Kelvin-Helmholtz instability of the magnetopause

The effect of finite ion Larmor radius on the Kelvin-Hehnholtz instability of the Earth's magnetopause is theoretically investigated when a wave vector is perpendicular to a magnetic field. It is found that a dawn-dusk asymmetry in excited waves is caused by this effect. This result is discussed in comparison with satellite observations.     

Gravitational instability of a rotating plasma

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.     

Kinetic Alfven wave in the presence of general loss-cone distribution function in inhomogeneous magnetoplasma—particle aspect analysis

Particle aspect analysis is extended for kinetic Alfven waves in an inhomogeneous magnetoplasma in the presence of a general loss-cone distribution function. The effect of finite Larmor radius is incorporated in the finite temperature anisotropic plasma. Expressions for the field-aligned current, perpendicular current (to B), dispersion relation, particle energy and growth rate are derived and effects of steepness of loss-cone distribution and plasma density inhomogeneity are discussed. The treatment of the kinetic Alfven wave instability is based on the assumption that the plasma consists of resonant and non-resonant particles. It is assumed that resonant particles support the oscillatory nature of the wave. The excitation of the wave is treated by the wave particle energy exchange method. The applicability of the investigation is discussed for auroral acceleration phenomena. © 1999 Elsevier Science Ltd. All rights reserved.     

Magneto-gravitational instability of a fluid through porous medium including finite ion Larmor radius

The magneto-gravitational instability of an infinite, homogenous, and infinitely conducting plasma flowing through a porous medium is studied. The finite ion Larmor radius (FLR) effects and viscosity are also incorporated in the analysis. The prevalent magnetic field is assumed to be uniform and acting in the vertical direction. A general dispersion relation has been obtained from the relevant linearized perturbation equations of the problem. The wave propagation parallel and perpendicular to the direction of the magnetic field have been discussed. It is found that the condition of the instability is determined by the Jeans criterion for a self-gravitating, infinitely conducting, magnetized fluid through a porous medium. Furthermore, for transverse perturbation FLR is found to have stabilizing influence when the medium is considered inviscid.     

Effect of Hall Current and Finite Larmor Radius Corrections on Thermal Instability of Radiative Plasma for Star Formation in Interstellar Medium (ISM)

The effects of finite ion Larmor radius (FLR) corrections, Hall current and radiative heat-loss function on the thermal instability of an infinite homogeneous, viscous plasma incorporating the effects of finite electrical resistivity, thermal conductivity and permeability for star formation in interstellar medium have been investigated. A general dispersion relation is derived using the normal mode analysis method with the help of relevant linearized perturbation equations of the problem. The wave propagation is discussed for longitudinal and transverse directions to the external magnetic field and the conditions of modified thermal instabilities and stabilities are discussed in different cases. We find that the thermal instability criterion gets modified into radiative instability criterion. The finite electrical resistivity removes the effect of magnetic field and the viscosity of the medium removes the effect of FLR from the condition of radiative instability. The Hall parameter affects only the longitudinal mode of propagation and it has no effect on the transverse mode of propagation. Numerical calculation shows stabilizing effect of viscosity, heat-loss function and FLR corrections, and destabilizing effect of finite resistivity and permeability on the thermal instability. The outcome of the problem discussed the formation of star in the interstellar medium.