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SUMMARY:Angular momentum transport in electrically-conducting fluids - Dr.
  Cristophe Gissinger - ENS Paris
DTSTART:20211018T130000Z
DTEND:20211018T140000Z
UID:TALK161824@talks.cam.ac.uk
CONTACT:Callum William Fairbairn
DESCRIPTION:The radial transport of angular momentum is a central quantity
  in astrophysics\, as it is an essential ingredient in the dynamics of man
 y objects\, among which the best known are accretion discs or radiative st
 ars. In both cases\, the mechanism that generates the turbulence and the a
 mount of angular momentum transported outward remain to be clearly identif
 ied.\n\nIn this talk\, I will first describe a new laboratory experiment 
 in which a Couette flow is driven by an electromagnetic force rather than 
 by the rotation of the boundaries. When the electromagnetic force applied 
 to the liquid metal is large enough\, the experiment provides a configurat
 ion analogous to astrophysical disks\, characterized by a fully turbulent 
 flow that exhibits Keplerian rotation rates. The angular momentum is then 
 transported through a non-dissipative regime\, yielding predictions for th
 e accretion rates of astrophysical disks.\n\nIn a second part\, I will des
 cribe global numerical simulations aiming to model a radiative stellar lay
 er. For some parameters\, we report the existence of a subcritical transit
 ion to turbulence due to the\ngeneration of a dynamo magnetic field\, ver
 y similar to the Tayler-Spruit model. This regime significantly enhances t
 ransport in radiative zones\, leading to a drastic spin-down of the inner 
 part of the star.
LOCATION:Online
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