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SUMMARY:Recent dynamo results in DNS of stably stratified stars - Florenti
 n Daniel (CNRS - Ecole Normale Superieure Paris)
DTSTART:20220916T101500Z
DTEND:20220916T110000Z
UID:TALK177530@talks.cam.ac.uk
DESCRIPTION:with L. Petitdemange\, C.Gissinger and F.Marcotte\nDynamo acti
 on in a stably stratified regime have long been investigated both numerica
 lly and theoretically for modelling MHD astrophysical objects such as star
 s\, but it&rsquo\;s only recently that such a regime could be found by run
 ning Direct Numerical Simulations. The so-called Tayler-Spruit dynamo inte
 restingly maintains a magnetic field by generating a source of turbulence 
 in the stable region\, and this is even done below know thresholds of hydr
 odynamical instabilities. We investigate the subcritical nature of this dy
 namo in terms of fluctuations and prove that it relies on a constant magne
 tic Reynolds number if the rotation and stratification are fixed. Isolatin
 g the key dynamical modes we propose a low dimensional model reproducing t
 his subcriticality involving only three modes\, highlighting the interacti
 on between hydrodynamical and magnetic instabilities. Eventually\, we disc
 uss the role of the dynamo on turbulent transport coefficients and see how
  our measurements compare to previous theories.
LOCATION:Seminar Room 1\, Newton Institute
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