## On the dynamo driven accretion disks
^{1} Max-Planck Institute für Radioastronomie, Auf dem
Hügel 69, D-53121 Bonn, Germany^{2} Purple Mountain Observatory, Academia Sinica, Nanjing
210008, P.R. China
We add the effect in the dynamo driven accretion disk model proposed by Tout & Pringle (1992), i.e., a dynamo model depends on the physical processes such as Parker instability, B-H instability, magnetic field reconnection and mean field dynamo as well. The effect in the dynamo mechanism is determined by the strength of turbulence of the accretion flow. When the turbulent Mach number is less than 0.25, the solutions of the magnetic fields oscillate around their equilibrium values. Increasing the value of makes the amplitude of the oscillation smaller and the period longer, but does not affect the equilibrium values. The Shakura-Sunyaev viscosity parameter oscillates around the equilibrium value of 0.33. When the turbulent Mach number is larger than 0.25, the magnetic field components reach a stable state. In the non-linear dynamo region, the critical turbulent Mach number is 0.44 rather than 0.25. The oscillating magnetic fields and viscosity parameter can explain the basic properties of the dwarf nova eruptions and some properties of quiescent disks (Armitage et al. 1996).
## Contents- 1. Introduction
- 2. The model
- 2.1. Parker instability
- 2.2. Balbus-Hawley instability
- 2.3. The dynamo
- 2.4. Dissipation of the magnetic energy
- 2.5. The source of turbulence
- 2.6. The full dynamo equations
- 3. Solutions of the dynamo equations
- 3.1. The equilibrium solutions
- 3.2. The numerical solution
- 3.3. The non-linear dynamo
- 4. Conclusion and discussion
- Acknowledgements
- References
© European Southern Observatory (ESO) 1998 Online publication: May 15, 1998 |