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PRODID:UW-Madison-Physics-Events
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UID:UW-Physics-Event-1346
DTSTART:20081124T220000Z
DURATION:PT1H0M0S
DTSTAMP:20260430T023652Z
LAST-MODIFIED:20081124T155207Z
LOCATION:2241 Chamberlin Hall (Coffee and cookies at 3.30 pm)
SUMMARY:Studying Astrophysics in the Laboratory: How is Angular Moment
 um Rapidly Transported in Accretion Disks?\, Physics Department Colloq
 uium\, Hantao Ji\, Center for Magnetic Self-Organization in Laboratory
  and Astrophysical Plasmas\, Princeton Plasma Physics Laboratory\, Pri
 nceton University
DESCRIPTION:Rapid angular momentum transport in accretion disk plasmas
  has been a longstanding astrophysical puzzle. Since Keplerian flows a
 re linearly stable in hydrodynamics\, there exist only two viable mech
 anisms for the required turbulence: nonlinear hydrodynamic instability
  or linear magnetorotational instability (MRI). The latter is consider
 ed operating in hot disks ranging from quasars and X-ray binaries to c
 ataclysmic variables. The former has been proposed mainly for cooler p
 rotoplanetary disk plasmas\, whose Reynolds numbers are enormous. Desp
 ite their popularity\, however\, both candidate mechanisms have been r
 arely demonstrated and studied in the laboratory. In this talk\, I wil
 l describe a novel laboratory experiment in a short Taylor-Couette flo
 w geometry intended for such purposes. The experiments in water have s
 hown\, rather surprisingly\, that quasi-Keplerian flows at Reynolds nu
 mbers as large as two millions are essentially laminar\, effectively r
 uling out hydrodynamic turbulence as a candidate mechanism. The experi
 ments in liquid gallium eutectic by imposing an axial magnetic field h
 ave shown the emergence of nonaxisymmetric modes identified as magneto
 coriolis waves\, one branch of which should become the MRI at higher s
 peeds.
URL:https://www.physics.wisc.edu/events/?id=1346
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