Steven A. Balbus, working with John F. Hawley, established the astrophysical importance of the magnetorotational instability in weakly magnetized accretion disks. Their local linear stability analysis identified an instability associated with outward-decreasing angular velocity, even where the unmagnetized flow would pass the Rayleigh centrifugal stability criterion.[ref]
The result offered a route from differential rotation to fluid fluctuations and outward angular momentum transport, allowing gas to accrete without attributing the transport to molecular viscosity alone.
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