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COUNTERROTATING
ACCRETION DISKS
Authors:
R.V.E. Lovelace and Tom Chou
We consider accretion disks consisting of counterrotating gaseous
components with an intervening shear layer. Configurations of this type may arise from the
accretion of newly supplied counterrotating gas onto an existing corotating gas
disk. For
simplicity we consider the case where the gas well above the disk midplane is rotating
with angular rate +W and that well below has the same properties but is rotating with
rate -W. Using the Shakura-Sunyaev alpha
turbulence model, we find self-similar solutions where a thin (relative to the full disk
thickness) equatorial layer accretes very rapidly, essentially at free-fall speed. As a
result, the accretion speed is much larger than it would be for an alpha disk rotating in
one direction. Counterrotating accretion disks may be a transient stage in the formation
of counterrotating galaxies and in the accretion of matter onto compact objects.
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