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SUMMARY:MHD turbulence and state changes in compact X-ray sources - Steve 
 Balbus (Oxford)
DTSTART:20140206T163000Z
DTEND:20140206T173000Z
UID:TALK49660@talks.cam.ac.uk
CONTACT:Simon Hodgkin
DESCRIPTION:*Abstract*\n\nThere is evidence that the saturation levels of 
 MHD turbulence are\nsensitive to the ratio of the small scale viscosity to
  resistivity\,\na quantity known as the magnetic Prandtl number Pm.  This 
 sensitivity is present when Pm  ~ 1.   \n\nInterestingly\, discs associate
 d with compact X-ray sources have such a low-to-high (tracking inward) Pm 
 transition radius on scales of tens of Schwarzschild radii. These disc sou
 rces are also known for their dramatic changes in their spectral states.  
 \n\nIn this talk\, I will show that standard alpha disc theory predicts Dw
 arf-Nova like outbursts when the turbulent stress is even a modestly incre
 asing function of Pm.  Implications for understanding the X-ray data will 
 be presented\, both successes of the theory and remaining challenges.
LOCATION:Sackler Lecture Theatre\, IoA (tea at 4:00 pm)
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