On properties of Velikhov–Chandrasekhar MRI in ideal and non-ideal plasma

Conditions of Velikhov–Chandrasekhar magnetorotational instability (MRI) in ideal and non-ideal plasmas are examined. Linear WKB analysis of hydromagnetic axially symmetric flows shows that in the Rayleigh-unstable hydrodynamic case where the angular momentum decreases with radius, the MRI branch be...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2015-04, Vol.448 (4), p.3697-3706
Main Authors: Shakura, N., Postnov, K.
Format: Article
Language:English
Subjects:
Accretion disks
Astronomy
Constraining
Fluid dynamics
Fluid flow
Fluid mechanics
Hydrodynamics
Hydromagnetics
Instability
Magnetic fields
Stability
Viscosity
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Summary:Conditions of Velikhov–Chandrasekhar magnetorotational instability (MRI) in ideal and non-ideal plasmas are examined. Linear WKB analysis of hydromagnetic axially symmetric flows shows that in the Rayleigh-unstable hydrodynamic case where the angular momentum decreases with radius, the MRI branch becomes stable, and the magnetic field suppresses the Rayleigh instability at small wavelengths. We investigate the limiting transition from hydromagnetic flows to hydrodynamic flows. The Rayleigh mode smoothly transits to the hydrodynamic case, while the Velikhov–Chandrasekhar MRI mode completely disappears without the magnetic field. The effects of viscosity and magnetic diffusivity in plasma on the MRI conditions in thin accretion discs are studied. We find the limits on the mean-free path of ions allowing MRI to operate in such discs.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stu2560