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SUMMARY:Magnetised shearing box simulations with temperature-dependent res
 istivity. - Pierre Lesaffre (ENS\, Paris)
DTSTART:20080516T140000Z
DTEND:20080516T150000Z
UID:TALK11340@talks.cam.ac.uk
CONTACT:Dr Lara Silvers
DESCRIPTION:Magnetised Keplerian disks are subject to the magnetorotationa
 l instability (MRI) which is believed to drive their state of turbulence. 
 Isothermal shearing box simulations with a mean magnetic field have shown 
 that the resistivity controls the saturation state of the MRI: low resisti
 vity yields  sustained turbulence (active state\, hot and\nmagnetised) whe
 reas strong resistivity shuts it off (dead state\, cold and unmagnetised).
  Since the resistivity is generally a (decreasing)\nfunction of temperatur
 e\, the heating due to the dissipation of turbulence provides an interesti
 ng backreaction on the system.\n\n  I will show how a very schematic model
  can account for the transition between such two states\, which can be vie
 wed as a system with two stable phases. I will then report on shearing box
  simulations (with a mean\nfield) where heating\, cooling and the temperat
 ure-dependence of the resistivity have been included. These simulations al
 l display strong recurrent or persistent channel flows. I will show how cr
 ucial the aspect ratio of the computational box appears to be. I will fina
 lly hint at how the parasitic instabilities of the channel flow might be a
 t the heart of the saturation process of mean field simulations.\n
LOCATION:MR14\, DAMTP\, Pav. F
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