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Magnetorotational instability driven dynamos at low magnetic Prandtl numbers
Article first published online: 5 FEB 2011
DOI: 10.1111/j.1365-2966.2010.18184.x
© 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
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How to Cite
Käpylä, P. J. and Korpi, M. J. (2011), Magnetorotational instability driven dynamos at low magnetic Prandtl numbers. Monthly Notices of the Royal Astronomical Society, 413: 901–907. doi: 10.1111/j.1365-2966.2010.18184.x
Publication History
- Issue published online: 25 APR 2011
- Article first published online: 5 FEB 2011
- Accepted 2010 December 9. Received 2010 November 9; in original form 2010 April 14
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Keywords:
- accretion, accretion discs;
- magnetic fields;
- MHD;
- turbulence
ABSTRACT
Numerical simulations of the magnetorotational instability (MRI) with zero initial net flux in a non-stratified isothermal cubic domain are used to demonstrate the importance of magnetic boundary conditions. In fully periodic systems, the level of turbulence generated by the MRI strongly decreases as the magnetic Prandtl number (Pm), which is the ratio of kinematic viscosity and magnetic diffusion, is decreased. No MRI or dynamo action below Pm = 1 is found, agreeing with earlier investigations. Using vertical field conditions, which allow the generation of a net toroidal flux and magnetic helicity fluxes out of the system, the MRI is found to be excited in the range 0.1 ≤ Pm ≤ 10, and the saturation level is independent of Pm. In the vertical field runs, strong mean-field dynamo develops and helps to sustain the MRI.