Journal Article

MRI channel flows and their parasites

Henrik N. Latter, Pierre Lesaffre and Steven A. Balbus

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 394, issue 2, pages 715-729
Published in print April 2009 | ISSN: 0035-8711
Published online March 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14395.x
MRI channel flows and their parasites

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Local simulations of the magnetorotational instability (MRI) in accretion discs can exhibit recurrent coherent structures called channel flows. The formation and destruction of these structures may play a role in the development and saturation of MRI-induced turbulence, and consequently help us understand the time-dependent accretion behaviour of certain astrophysical objects. Previous investigations have revealed that channel solutions are attacked by various parasitic modes, foremost of which is an analogue of the Kelvin–Helmholtz instability. We revisit these instabilities and show how they relate to the classical instabilities of plasma physics, the kink and pinch modes. However, we argue that in most cases channels emerge from developed turbulence and are eventually destroyed by turbulent mixing, not by the parasites. The exceptions are clean isolated channels, which appear in systems near criticality or which emerge from low amplitude initial conditions. These structures can achieve large amplitudes and are only then destroyed, giving rise to eruptive behaviour.

Keywords: accretion, accretion discs; instabilities; MHD; turbulence

Journal Article.  12767 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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