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Global MHD simulations of disk-magnetosphere interactions: accretion and outflows

Published online by Cambridge University Press:  08 June 2011

M. M. Romanova ,
R. V. E. Lovelace ,
G. V. Ustyugova  and
A. V. Koldoba
M. M. Romanova
Affiliation:
Department of Astronomy, Cornell University, Ithaca, NY 14853-6801 email: [email protected]
R. V. E. Lovelace
Affiliation:
Department of Astronomy and Department of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853-6801 email: [email protected]
G. V. Ustyugova
Affiliation:
Keldysh Institute of Applied Mathematics Russian Academy of Sciences, Moscow, Russia email: [email protected]; [email protected]
A. V. Koldoba
Affiliation:
Keldysh Institute of Applied Mathematics Russian Academy of Sciences, Moscow, Russia email: [email protected]; [email protected]
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Abstract

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We outline recent progress in understanding the accretion of plasma to rotating magnetized stars obtained from global axisymmetric (2D) and 3D magnetohydrodynamic (MHD) simulations in three main areas: (1.) Formation of jets from disk accretion onto rotating magnetized stars: From simulations where the viscosity and magnetic diffusivity within the disk are described by alpha models, we find long-lasting conical outflows/jets from the disk/magnetosphere boundary in both the case where the star is slowly rotating and where it is rapidly rotating (the “propeller regime”). Most of the mass flux in the outflows is in a hollow cone but inside this cone there is a low-density high-velocity magnetically dominated flow along the open polar field lines of the star. The outflows occur under conditions where the poloidal magnetic flux of the star is bunched up by the accretion disk near the disk/magnetosphere boundary. Recent simulations show that the conical outflows become well-collimated for axial distances of ≲ 20 times the inner disk radius. Exploratory 3D simulations show that conical winds are axisymmetric about the rotational axis (of the star and the disk), even when the dipole field of the star is significantly misaligned. (2.) Formation of intrinsically one-sided jets from disk accretion to rotating magnetized stars: There is strong observational evidence for an asymmetry between the approaching and receding jets from a number of young stars. We discuss the first MHD simulations of the formation asymmetric or one-sided jets arising from disk accretion to a rotating star with an asymmetric (dipole plus quadrupole) magnetic field. (3.) Global axisymmetric and 3D simulations of the magnetorotational instability (MRI) in disk accretion onto magnetized stars: In the axisymmetric simulations we observe cases where there is episodic or quasi-periodic burst of accretion similar to that observed in one X ray source. In 3D MHD simulations of accretion onto stars with tilted dipole fields using our Godunov-type code based on the “cubed sphere” grid we find that the density distribution is much less smooth than in the case of the laminar accretion flow described by α–viscosity. Instead, large turbulent cells dominate the flows and are strongly elongated in the azimuthal direction.

Keywords

accretionaccretion disksMHDstars: magnetic fields
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S274: Advances in Plasma Astrophysics , September 2010 , pp. 416 - 421
Copyright
Copyright © International Astronomical Union 2011

References

Bacciotti, F., Eisloffel, J., & Ray, T. P. 1999, A&A, 350, 917Google Scholar
Balbus, S. A. & Hawley, J. F. 1991, ApJ, 376, 214CrossRefGoogle Scholar
Balbus, S. A. & Hawley, J. F. 1998, Rev. Mod. Phs., Volume 70, 1–53CrossRefGoogle Scholar
Beckwith, K., Hawley, J. F., & Krolik, J. H. 2009, ApJ, 707, 428CrossRefGoogle Scholar
Cabrit, S., Edwards, S., Strom, S. E., & Strom, K. M. 1990, ApJ, 354, 687Google Scholar
Coffey, D., Bacciotti, F., Woitas, J., Ray, T. P., & Eislöffel, J. 2004, ApJ, 604, 758CrossRefGoogle Scholar
Donati, J.-F. et al. . 2008, MNRAS, 386, 1234CrossRefGoogle Scholar
Ferreira, J, Dougados, C., & Cabrit, S. 2006, A&A, 453, 785Google Scholar
Hawley, J. F, Balbus, S. A., & Stone, J. M. 2001, ApJ Letters, 554, L49–L52CrossRefGoogle Scholar
Koldoba, A. V., Romanova, M. M., Ustyugova, G. V., & Lovelace, R. V. E. 2002, ApJ, 576, L53–L56CrossRefGoogle Scholar
Königl, A. & Pudritz, R. E. 2000, Protostars and Planets IV, Mannings, V., Boss, A. P., Russell, S. S. (eds.), University of Arizona Press, Tucson, p. 759Google Scholar
Lii, P., Romanova, M. M., & Lovelace, R. V. E. 2010, in preparationGoogle Scholar
Livio, M. 1997, Accretion Phenomena and Related Outflows; IAU Colloquium 163. ASP Conference Series; Vol. 121; ed. Wickramasinghe, D. T.; Bicknell, G. V.; and Ferrario, L., p. 845CrossRefGoogle Scholar
Lovelace, R. V. E., Romanova, M. M., Ustyugova, G. V., & Koldoba, A. V. 2010, MNRAS, 408, 2083CrossRefGoogle Scholar
Lovelace, R. V. E., Berk, H. L., & Contopoulos, J. 1991, ApJ, 379, 696CrossRefGoogle Scholar
Patruno, A., Wijnands, R., van der Klis, M. 2009b, ApJ, 698, L60–L63CrossRefGoogle Scholar
Perrin, M. D.,& Graham, J. R. 2007, ApJ, 670, 499CrossRefGoogle Scholar
Ray, T., Dougados, C., Bacciotti, F., Eislffel, J., & Chrysostomou, A. 2007, Protostars and Planets V, Reipurth, B., Jewitt, D., and Keil, K. (eds.), University of Arizona Press, Tucson, p. 231Google Scholar
Romanova, M. M., Ustyugova, G. V., Koldoba, A. V., & Lovelace, R. V. E. 2009, ApJ, 399, 1802Google Scholar
Romanova, M. M. et al. . 2011a, in preparationGoogle Scholar
Romanova, M. M. et al. . 2011b, in preparationGoogle Scholar
Shakura, N. I. & Sunyaev, R. A. 1973, A&A, 24, 337Google Scholar
Shu, F., Najita, J., Ostriker, E., Wilkin, F., Ruden, S., & Lizano, S. 1994, ApJ, 429, 781Google Scholar
Woitas, J., Ray, T. P., Bacciotti, F., Davis, C. J., & Eislöffel, J. 2002, ApJ, 580, 336CrossRefGoogle Scholar