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PROPELLER-DRIVEN OUTFLOWS AND DISK OSCILLATIONS
Authors:
Romanova
M.M., Ustyugova G.V., Koldoba A.V. and Lovelace R. V. E.
We report the discovery of propeller-driven outflows in axisymmetric
magnetohydrodynamic simulations of disk accretion to rapidly rotating magnetized
stars. Matter outflows in a wide cone and is centrifugally ejected from the
inner regions of the disk. Closer to the axis there is a strong, collimated,
magnetically dominated outflow of energy and angular momentum
carried by the open magnetic field lines from the star. The ``efficiency'' of
the propeller may be very high in the respect that most of the incoming disk
matter is expelled from the system in winds. The star spins-down rapidly due to
the magnetic interaction with the disk through closed field lines and with
corona through open field lines. Diffusive and viscous interaction between
magnetosphere and the disk are important: no outflows were observed for very
small values of the diffusivity and viscosity. These simulation results are
applicable to the early stages of evolution of classical T Tauri stars and to
different stages of evolution of cataclysmic variables and neutron stars in
binary systems. As an example, we have shown that young rapidly rotating
magnetized CTTSs spin-down to their present slow rotation in less than 106
years.
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