Guseva, A., Willis, A.P. orcid.org/0000-0002-2693-2952, Hollerbach, R. et al. (1 more author) (2017) Transport properties of the azimuthal magnetorotational instability. Astrophysical Journal , 849 (2). ISSN 0004-637X
Abstract
The magnetorotational instability (MRI) is thought to be a powerful source of turbulence in Keplerian accretion disks. Motivated by recent laboratory experiments, we study the MRI driven by an azimuthal magnetic field in an electrically conducting fluid sheared between two concentric rotating cylinders. By adjusting the rotation rates of the cylinders, we approximate angular velocity profiles ω ∝ r q . We perform direct numerical simulations of a steep profile close to the Rayleigh line q & −2 and a quasiKeplerian profile q ≈ −3/2 and cover wide ranges of Reynolds (Re ≤ 4 · 104 ) and magnetic Prandtl numbers (0 ≤ Pm ≤ 1). In the quasi-Keplerian case, the onset of instability depends on the magnetic Reynolds number, with Rmc ≈ 50, and angular momentum transport scales as √ PmRe2 in the turbulent regime. The ratio of Maxwell to Reynolds stresses is set by Rm. At the onset of instability both stresses have similar magnitude, whereas the Reynolds stress vanishes or becomes even negative as Rm increases. For the profile close to the Rayleigh line, the instability shares these properties as long as Pm & 0.1, but exhibits a markedly different character if Pm → 0, where the onset of instability is governed by the Reynolds number, with Rec ≈ 1250, transport is via Reynolds stresses and scales as Re2 . At intermediate Pm = 0.01 we observe a continuous transition from one regime to the other, with a crossover at Rm = O(100). Our results give a comprehensive picture of angular momentum transport of the MRI with an imposed azimuthal field.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2017 American Astronomical Society. Reproduced in accordance with the publisher's self-archiving policy. |
Keywords: | magnetohydrodynamics; instabilities; turbulence |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematics and Statistics (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 06 Oct 2017 14:03 |
Last Modified: | 07 Nov 2017 15:36 |
Published Version: | https://doi.org/10.3847/1538-4357/aa917d |
Status: | Published |
Publisher: | American Astronomical Society |
Refereed: | Yes |
Identification Number: | 10.3847/1538-4357/aa917d |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:122048 |