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SUMMARY:Contributed talk: Transition from multipolar to dipolar dynamos in
  stratified systems - Bonnie Zaire (Universidade Federal de Minas Gerais (
 UFMG))
DTSTART:20221201T150000Z
DTEND:20221201T153000Z
UID:TALK192143@talks.cam.ac.uk
DESCRIPTION:Observations of surface magnetic fields of cool stars reveal a
  large diversity of configurations. Although there is now a consensus that
  these fields are generated through dynamo processes occurring within the 
 convective zone\, the physical mechanism driving such a variety of field t
 opologies is nonetheless in debate. In this talk\, we propose to discuss t
 he possible origins of dipole and multipole-dominated morphologies using t
 hree-dimensional numerical simulations of stratified systems where the mag
 netic feedback on the fluid motion is significant. After introducing previ
 ous studies focused on understanding the emergence of dipole-dominated or 
 complex multipolar-dominated field topologies\, we will show that dipolar 
 solutions can be found at Rossby numbers up to 0.4 in strongly stratified 
 simulations\, where previous works suggested that only multipolar fields s
 hould exist. We argue that these simulations are reminiscent of the outlie
 r stars observed at Rossby numbers larger than 0.1\, whose large-scale mag
 netic field is dominated by their axisymmetric poloidal component. We anal
 yse how well different proxies can capture the transition in the field mor
 phology in our simulations. Finally\, we test their ability to predict the
  magnetic morphology of a few M-dwarf stars whose internal structure match
 es that of our simulations and for which homogeneous magnetic field charac
 terisation is available.
LOCATION:Seminar Room 1\, Newton Institute
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