A UNIFYING PICTURE OF HELICAL AND AZIMUTHAL MAGNETOROTATIONAL INSTABILITY, AND THE UNIVERSAL SIGNIFICANCE OF THE LIU LIMIT

Journal Article · Sat Sep 01 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/756/1/83· OSTI ID:22092419

Kirillov, Oleg N.; Stefani, Frank ^[1]; Fukumoto, Yasuhide ^[2]

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1. Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden (Germany)
2. Institute of Mathematics for Industry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)

The magnetorotational instability (MRI) plays a key role for cosmic structure formation by triggering turbulence in the rotating flows of accretion disks that would be otherwise hydrodynamically stable. In the limit of small magnetic Prandtl number, the helical and the azimuthal versions of MRI are known to be governed by a quite different scaling behavior than the standard MRI with a vertical applied magnetic field. Using the short-wavelength approximation for an incompressible, resistive, and viscous rotating fluid, we present a unified description of helical and azimuthal MRI, and we identify the universal character of the Liu limit 2(1-{radical}2){approx}-0.8284 for the critical Rossby number. From this universal behavior we are also led to the prediction that the instability will be governed by a mode with an azimuthal wavenumber that is proportional to the ratio of axial to azimuthal applied magnetic field, when this ratio becomes large and the Rossby number is close to the Liu limit.

• OSTI ID: 22092419
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 756; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
APPROXIMATIONS
ASTRONOMY
ASTROPHYSICS
COSMOLOGY
INSTABILITY
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
PRANDTL NUMBER
TURBULENCE
WAVELENGTHS