Influence of the diamagnetic effect on the magnetorotational instability in accretion discs

We show that in protostellar discs the diamagnetic effect modifies the magnetorotational instability (MRI) that exists in the presence of the Hall electromotive force. We also make clear that the inclusion of magnetization into the governing magnetohydrodynamics equations does not weaken the unstabl...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2007-05, Vol.377 (3), p.1245-1262
Main Authors: Devlen, E., Pekünlü, E. R.
Format: Article
Language:English
Subjects:
accretion
accretion discs
Accretion disks
accretion, accretion discs
Astronomy
Earth, ocean, space
Exact sciences and technology
instabilities
Magnetic fields
MHD
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Summary:We show that in protostellar discs the diamagnetic effect modifies the magnetorotational instability (MRI) that exists in the presence of the Hall electromotive force. We also make clear that the inclusion of magnetization into the governing magnetohydrodynamics equations does not weaken the unstable character of the disc. The maximum growth rate of the unstable mode exceeds the local Oort A-value. Another novel result is that the magnetic field gradient produced by the magnetization current in active zones produces an unstable mode, which drives the MRI when the magnetic moment and rotation axes are perpendicular.
ISSN:0035-8711
1365-2966
DOI:10.1111/j.1365-2966.2007.11677.x