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VERSION:2.0
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PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-4531
DTSTART:20170406T203000Z
DTEND:20170406T220000Z
DTSTAMP:20260419T060235Z
LAST-MODIFIED:20170329T161653Z
LOCATION:4421 Sterling Hall\, Coffee and cookies at 3:30 PM\, Talk beg
 ins at 3:45 PM
SUMMARY:Turbulence and Dynamo Action in Accretion Flows\, Astronomy Co
 lloquium\, Fausto Cattaneo\, University of Chicago
DESCRIPTION:Accretion is an important process in astrophysics: it allo
 ws the growth of compact objects and it powers some of the most energe
 tic phenomena in the universe. Often the accreting material comes from
  a disk. In this case the accretion rate is controlled by the outward 
 flux of angular momentum.  Collisional process\, like viscosity\, are 
 many orders of magnitude too small to provide the efficient angular mo
 mentum transport required to account for the observed accretion rates.
  Thus it is commonly assumed that the transport in an accretion disk i
 s mediated by some form of turbulence. The nature of this turbulence i
 s a matter of intense debate. In electrically conducting disks\, its o
 rigin is most likely related to the Magneto Rotational Instability (MR
 I)\, which requires that the disk be threaded by a coherent weak magne
 tic field. This raises the interesting possibility that the disk turbu
 lence\, through dynamo action\, may be able to generate the very magne
 tic filed that is necessary for the instability to develop. This proce
 ss of self-sustaining magnetization has indeed been observed in numeri
 cal simulations. However many issues remain\, the most notable of whic
 h are the ability of the MRI driven dynamo to operate in the limit of 
 high electrical conductivity and the efficiency of the angular momentu
 m transport. In this talk I shall describe some of the efforts to date
  to address these issues.
URL:https://www.physics.wisc.edu/events/?id=4531
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