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Axisymmetric magneto-rotational instability in viscous accretion disks

Published online by Cambridge University Press:  01 November 2008

Youhei Masada
Affiliation:
Institute of Astronomy and Astrophysics, Academia Sinica email: masada@asiaa.sinica.edu.tw
Takayoshi Sano
Affiliation:
Institute of Laser Engineering, Osaka University; email: sano@ile.osaka-u.ac.jp
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Abstract

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Axisymmetric MRI in viscous accretion disks is investigated. The linear growth of the viscous MRI is characterized by the Reynolds number RMRIv2A/νΩ, where vA is the Alfvén velocity, ν is the kinematic viscosity, and Ω is the angular velocity of the disk. Although the linear growth of the MRI is suppressed as the Reynolds number decreases, its nonlinear behavior is found to be almost independent of RMRI. At the nonlinear stage, the channel flow grows and the Maxwell stress increases even though RMRI is much smaller than unity. Nonlinear behavior of the MRI in the viscous regime can be explained by the characteristics of the linear dispersion relation. Applying our results to the case with both viscosity and resistivity, it is anticipated that the critical value of the Lundquist number SMRIv2A/ηΩ for active turbulence would depend on the magnetic Prandtl number Pm ≡ ν/η, where η is the magnetic diffusivity.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2009

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