Spherical Bondi accretion onto a magnetic dipole 

Authors: Toropin Yu.M., Toropina O.D., Savelyev V.M., Romanova M.M., Chechetkin V.M., Lovelace R.V.E.

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Fig 1.     The figure shows an example of our calculated flow for accretion onto a non - rotating star with a dipole magnetic field. The background scale represents the density of the flow and the solid lines the poloidal magnetic field lines. The lengths of the arrows is proportional to flow speed. The internal circular region represents the "accretor". The shock wave and associated transition from supersonic to subsonic flow is evident. The flow becomes strongly anisotropic close to dipole. The simulations were done on a grid 257 x 257 cells in one quadrant of the physical space. Only one quadrant is needed due to the assumed axisymmetry and the symmetry about the equatorial plane.

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Fig 2.  Enlarged view of the inner region of the plot of fig 1. The anisotropy of the flow is evident. The torus-like region with small flow velocities is the "stagnation zone". In the equatorial plane, the outer boundary of this zone is the magnetopause. There are two polar accretion columns. The outer dashed line represent the Alfven surface. At very small distance from the star, the flow in polar columns becomes supersonic. The sonic surface is marked by dashed line in the region of polar columns.

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Fig 3.  The figure shows the accretion flow to a rapidly rotating star. The background scale represents the density and the solid lines the poloidal magnetic field. The lengths of the arrows is proportional to flow speed.

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Fig 4.  Enlarged view of the accretion flow to a rapidly rotating star with dipole field. The outer dashed line  the Alfven surface.   A inner sonic surface is indicated by the dashed line in the region polar columns. The outflow in the equatorial plane starts from the region of the corotation radius inside magnetosphere.

created by O. Toropina, 2000-2004Your comments are welcome
2000-2007, last updated on 29.01.07