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CATEGORIES:Colloquium/Seminar
DESCRIPTION:Dr. Allan Sacha Brun\, Dept. of Astrophysics\, CEA & University
  Paris-Saclay\, France\n\nPowering solar-type stars magnetism: how are magn
 etic cycles established and driven?\n\nWe present an extensive study on the
  dynamo origin of solar-type star's magnetism\, based on a large series of 
 3D MHD numerical simulations with the ASH code performed within the pan-Eur
 opean ERC project Whole Sun. We assess how the combination of rotation and 
 convection via the Rossby number influences the type of magnetism establish
 ed (short or long cycles\, statistically steady activity) and their expecte
 d differential rotation (solar-like\, anti-solar\, cylindrical or almost so
 lid). This large survey allows us to explain why the Sun possesses a long d
 ecadal cycle and a conical differential rotation. We further assess the amo
 unt of energy needed to maintain such angular velocity profiles and magneti
 c activity. We find that between 0.1 and 3% of the stellar luminosity can b
 e converted into magnetic energy\, giving plenty of energy for surface erup
 tive events to occur. We also compute the magnetic energy spectra and show 
 that the dipole and quadrupole magnetic fields do not collapse in amplitude
  when the rotation regime becomes anti-solar in agreement with spectropolar
 imetric observations\, and as such cannot simply explain a break of gyrochr
 onology for large Rossby number.\n\nFinally\, we discuss various scaling la
 ws that this study allows to derive and that could be tested with dedicated
  observations\, completing the current observational database. In particula
 r\, 2 regimes at low and high Rossby number seems particularly interesting 
 to further quantify and model.\n\nI will perhaps also briefly describe our 
 new Dyablo AMR code for stellar convection and dynamo.
DTEND:20221018T180000Z
DTSTAMP:20260314T052646Z
DTSTART:20221018T170000Z
GEO:40.006791;-105.262818
LOCATION:Engineering Center\, ECOT 317
SEQUENCE:0
SUMMARY:Mathematical Geosciences Seminar - Whitney Powers
UID:tag:localist.com\,2008:EventInstance_41340505661961
URL:https://calendar.colorado.edu/event/mathematical_geosciences_seminar_-_
 whitney_powers_613
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