Magnetorotational instability in stratified, weakly ionized accretion discs
Article
Article Title | Magnetorotational instability in stratified, weakly ionized accretion discs |
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ERA Journal ID | 1074 |
Article Category | Article |
Authors | Salmeron, Raquel (Author) and Wardle, Mark (Author) |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 345 (3), pp. 992-1008 |
Number of Pages | 17 |
Year | 2003 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1046/j.1365-8711.2003.07024.x |
Web Address (URL) | https://academic.oup.com/mnras/article/345/3/992/973620 |
Abstract | We present a linear analysis of the vertical structure and growth of the magnetorotational instability in stratified, weakly ionized accretion discs, such as protostellar and quiescent dwarf novae systems. The method includes the effects of the magnetic coupling, the conductivity regime of the fluid and the strength of the magnetic field, which is initially vertical. The conductivity is treated as a tensor and is assumed to be constant with height. We obtained solutions for the structure and growth rate of global unstable modes for different conductivity regimes, strengths of the initial magnetic field and coupling between ionized and neutral components of the fluid. The envelopes of short-wavelength perturbations are determined by the action of competing local growth rates at different heights, driven by the vertical stratification of the disc. Ambipolar diffusion perturbations peak consistently higher above the midplane than modes including Hall conductivity. For weak coupling, perturbations including the Hall effect grow faster and act over a more extended cross-section of the disc than those obtained using the ambipolar diffusion approximation. Finally, we derived an approximate criterion for when Hall diffusion determines the growth of the magnetorotational instability. This is satisfied over a wide range of radii in protostellar discs, reducing the extent of the magnetic 'dead zone'. Even if the magnetic coupling is weak, significant accretion may occur close to the midplane, rather than in the surface regions of weakly ionized discs. |
Keywords | Accretion, accretion discs; Instabilities; MHD; Stars: formation |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Public Notes | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2003 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | University of Sydney |
Macquarie University | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q735w/magnetorotational-instability-in-stratified-weakly-ionized-accretion-discs
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