Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010a%26a...513l...1k&link_type=abstract
Astronomy and Astrophysics, Volume 513, id.L1
Astronomy and Astrophysics
Astrophysics
3
Instabilities, Magnetohydrodynamics (Mhd), Magnetic Fields, Accretion, Accretion Disks
Scientific paper
Aims: Deviations from the axial symmetry are necessary to maintain self-sustained MRI-turbulence by a dynamo mechanism. We define the parameter region where the nonaxisymmetric MRI modes are excited and study their geometries and growth rates. Methods: The linear eigenvalue problem for global nonaxisymmetric modes of standard-MRI in Keplerian disks is solved numerically with allowance for finite diffusion. Results: For small magnetic Prandtl numbers the microscopic viscosity completely drops out of the analysis so that the stability maps and the growth rates expressed in terms of the magnetic Reynolds number Rm and the Lundquist number S do not depend on the magnetic Prandtl number Pm. The minimum magnetic field for the onset of nonaxisymmetric MRI grows with the rotation rate. For a given S all nonaxisymmetric modes disappear for a sufficiently large Rm. This is a consequence of the radial fine-structure of the nonaxisymmetric modes resulting from the winding effect of differential rotation. It is this fine-structure which also provides serious resolution problems for the numerical simulation of MRI at large Rm. Conclusions: For weak magnetic fields slightly above the critical value for the onset of MRI only axisymmetric modes are unstable. Nonaxisymmetric modes need stronger fields and not too large Rm. If Pm is small its real value does not play any role in MRI.
Kitchatinov Leonid L.
Rudiger Günther
No associations
LandOfFree
Nonaxisymmetric modes of MRI in dissipative Keplerian disks does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Nonaxisymmetric modes of MRI in dissipative Keplerian disks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nonaxisymmetric modes of MRI in dissipative Keplerian disks will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1800849