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SUMMARY:Relaxation of braided magnetic and vorticity fields - Hornig\, G\,
  Wilmot-Smith\, A\, Pontin\, D (University of Dundee)
DTSTART:20120726T084500Z
DTEND:20120726T090500Z
UID:TALK39069@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:In this talk we will first report on a series of numerical MHD
  experiments on the turbulent relaxation of braided magnetic fields in pla
 smas of high magnetic Reynolds numbers (Wilmot-Smith et al. 2009\, 2010). 
 These experiments have produced relaxed states which in some cases differ 
 drastically from the predictions of the Taylor hypothesis\, that is the as
 sumption that the final state of a turbulent relaxation is a linear force-
 free field with the same total helicity as the initial state. \n\nWe prese
 nt a method to determine the topological degree of the field line mapping 
 which shows that there are further constraints on the relaxation process b
 eyond the conservation of the total helicity (A. Yeates et al.\, Phys. Rev
 . Lett. 105\, 2010). These constraints can prevent the system from relaxin
 g to a Taylor state and hence limit the energy which can be released. \n\n
 We will then report on a new series of experiments where we test whether s
 imilar constraints hold in the hydrodynamic case\, that is we investigate 
 the relaxation of incompressible flows with braided vorticity field lines.
  \n
LOCATION:Seminar Room 1\, Newton Institute
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