Thermal-convective instability of a composite rotating stellar atmosphere in the presence of a variable magnetic field, medium permeability and solute gradient

1992 ◽  
Vol 198 (1) ◽  
pp. 21-28
Author(s):  
R. C. Sharma ◽  
Anup Rajput
Keyword(s):  
Magnetic Field ◽  
Convective Instability ◽  
Stellar Atmosphere ◽  
Variable Magnetic Field ◽  
Medium Permeability ◽  
Solute Gradient

The Thermal-Convective Instability in a Stellar Atmosphere with Rotation and Hall Effects

1974 ◽  
Vol 29 (6) ◽  
pp. 867-869 ◽  
Author(s):  
R. C. Sharma
Keyword(s):  
Magnetic Field ◽  
Convective Instability ◽  
Stellar Atmosphere ◽  
Vertical Magnetic Field ◽  
Hall Effects ◽  
Monotonic Instability

The problem of thermal-convective instability of a stellar atmosphere is considered to include the effects due to rotation and Hall currents in the presence of a uniform vertical magnetic field The criterion for monotonic instability is found to be unchanged by the presence of rotation and Hall effects.

Double-Diffusive Magneto Convection in a Compressible Couple-Stress Fluid Through Porous Medium

2011 ◽  
Vol 66 (5) ◽  
pp. 304-310 ◽  
Author(s):  
Pardeep Kumar ◽  
Hari Mohan
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Couple Stress ◽  
Mode Analysis ◽  
Couple Stress Fluid ◽  
Onset Of Convection ◽  
Linearized Stability ◽  
Medium Permeability ◽  
Solute Gradient ◽  
Double Diffusive

The double-diffusive convection in a compressible couple-stress fluid layer heated and soluted from below through porous medium is considered in the presence of a uniform vertical magnetic field. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the compressibility, stable solute gradient, magnetic field, and couple-stress postpone the onset of convection whereas medium permeability hastens the onset of convection. Graphs have been plotted by giving numerical values to the parameters to depict the stability characteristics. The stable solute gradient and magnetic field introduce oscillatory modes in the system, which were non-existent in their absence. A condition for the system to be stable is obtained by using the Rayleigh-Ritz inequality. The sufficient conditions for the non-existence of overstability are also obtained.

scholarly journals Thermosolutal-Convective Instability In Stern’s Type Configuration

2021 ◽  
Vol 20 ◽  
pp. 149-156
Author(s):  
Pardeep Kumar ◽  
Hari Mohan
Keyword(s):  
Radiative Transfer ◽  
Heat Loss ◽  
Loss Function ◽  
Convective Instability ◽  
Stellar Atmosphere ◽  
Transfer Effect ◽  
Composite Medium ◽  
Monotonic Instability ◽  
Solute Gradient ◽  
Frictional Effects

The thermal-convective instability of a stellar atmosphere in the presence of stable solute gradient in Stern’s type configuration is studied in the presence of radiative transfer effect. A criterion for monotonic instability is obtained in terms of the source functions S. The criterion for monotonic instability is found to be unchanged in the presence of radiative transfer and rotation effects. The problem of thermosolutal-convective instability of a hydromagnetic composite medium is also studied to include the frictional effects with neutrals. The criterion derived for monotonic instability in terms of heat-loss function is found to be the same in the presence or absence of the collisional effects.

scholarly journals Double-Diffusive Magnetoconvection of a Dusty Micropolar Fluid Saturating a Porous Medium

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Parul Aggarwal ◽  
Urvashi Gupta
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Micropolar Fluid ◽  
Fluid Layer ◽  
Suspended Particle ◽  
Suspended Particles ◽  
Linear Stability Theory ◽  
Stationary Convection ◽  
Medium Permeability ◽  
Solute Gradient

The paper deals with the theoretical investigation of the effect of dust/suspended particles on a layer of electrically conducting micropolar fluid heated and dissolved from below in the presence of a uniform vertical magnetic field in a porous medium. The presence of coupling between thermosolutal and micropolar effects and magnetic field brings oscillatory motions in the system. A dispersion relation governing the effects of solute gradient, magnetic field, and suspended particles is obtained for a fluid layer contained between two free boundaries using linear stability theory and normal mode technique. Graphs have been plotted by giving numerical values to various parameters involved to depict the stability characteristics for both cases of stationary convection and overstability. It has been found that, for permissible values of various parameters under consideration, the effect of magnetic field and solute gradient is stabilizing and that of medium permeability, suspended particles, and micropolar coefficient is destabilizing. Further it is found that the Rayleigh number for overstability is always less than that for stationary convection except for high values of suspended particle factor.

Rayleigh-Taylor Instability of a Partially Ionized Plasma in a Porous Medium in Presence of a Variable Magnetic Field

1992 ◽  
Vol 47 (12) ◽  
pp. 1227-1231
Author(s):  
R. C. Sharma ◽  
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Variable Magnetic Field ◽  
Taylor Instability ◽  
Wave Number ◽  
Medium Permeability ◽  
Wave Numbers ◽  
Rayleigh Taylor Instability ◽  
Partially Ionized ◽  
The Magnetic Field

Abstract The Rayleigh-Taylor instability of a partially ionized plasma in a porous medium is considered in the presence of a variable magnetic field perpendicular to gravity. The cases of two uniform partially ionized plasmas separated by a horizontal boundary and exponentially varying density, viscosity, magnetic field and neutral particle number density are considered. In each case, the magnetic field succeeds in stabilizing waves in a certain wave-number range which were unstable in the absence of the magnetic field, whereas the system is found to be stable for potentially stable configuration/stable stratifications. The growth rates both increase (for certain wave numbers) and decrease (for different wave numbers) with the increase in kinematic viscosity, medium permeability and collisional frequency. The medium permeability and collisions do not have any qualitative effect on the nature of stability or instability.

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