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SUMMARY:Special Astrophysical Fluid Dynamics Seminar: Probing convection a
 nd magnetic dynamos  deep within stars - Prof Juri Toomre.
DTSTART:20160318T143000Z
DTEND:20160318T153000Z
UID:TALK65036@talks.cam.ac.uk
CONTACT:Andrew Hillier
DESCRIPTION:The rich magnetism displayed by many stars\, including our sun
 \, must have their origin in dynamo action proceeding within their convect
 ion zones involving highly turbulent flows influenced by rotation and stra
 tification. The striking advances in seismic probing of stars is providing
  guidance about rotation states\, and possibly of magnetism\, deep within 
 a range of stars. This is complemented by supercomputing advances that now
  permit 3-D global simulations\, such as with our anelastic spherical harm
 onic (ASH) code\, of solar and stellar convection to study the nature of m
 agnetic dynamo action and differential rotation that can be achieved by co
 mplex flows involving a hierarchy of scales and patterns. In rotating sun-
 like stars with convective envelopes\, we have found using ASH modeling th
 at the resulting magnetic fields can exhibit remarkable large-scale struct
 ure involving wreaths of strong magnetism amidst the turbulent convection.
  These wreaths can involve temporal flips and even quite regular cycles. I
 n one prominent case that cycling with reversals was interrupted by a more
  quiescent interval\, after which the cycling resumed\, not unlike a Maund
 er Minimum. In more massive B-type rotating stars that have convective cor
 es and radiative envelopes\, we find with our ASH studies that core dynamo
  action can yield super-equipartition magnetic fields with mega-gauss stre
 ngths. These intense fields may have implications in later stages of evolu
 tion\, whether in the cores of red giants or in the survivors of supernova
  explosions. These overlaps in observations and computational theory make 
 for a period of major adventures in stellar astrophysics.
LOCATION:MR2\,  Centre for Mathematical Sciences\, Wilberforce Road\, Camb
 ridge
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