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SUMMARY:Invited speaker: Inference and simulation of large-scale core flow
  - Alexandre Fournier (Institut de Physique du Globe de Paris)
DTSTART:20221202T094500Z
DTEND:20221202T103000Z
UID:TALK192155@talks.cam.ac.uk
DESCRIPTION:(with Thomas Gastine)\nLarge-scale interannual to secular chan
 ges in Earth's magnetic field are caused by magnetic induction and\, to a 
 lesser extent\, by magnetic diffusion.Since 1999\,&nbsp\; the almost conti
 nuous observation of these changes by dedicated satellites enabled the inv
 estigation of their causes with an unprecedented level of accuracy -let us
  hope that this will continue after the Swarm mission ends! In particular\
 , several wavy patterns have been identified at the top of the core\, and 
 tentatively ascribed to certain categories of waves whose existence is pre
 dicted by theory.\nWaves will be discussed at length during the workshop\;
  here I will instead review the properties of the background flow on top o
 f which these waves ride. The background flow\, which varies on convective
  (secular) time scales\, consists of a planetary scale circulation compris
 ing a strong westward current at low latitude under the Atlantic ocean and
  a high-latitude jet close to the tangent cylinder under Siberia and Canad
 a.&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&n
 bsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\
 ;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;\nI will discuss the ability of dynamo
  models to account for these properties\, and more generally\, what curren
 t simulations can and can not achieve\, notably in the light of the output
  of an extreme direct numerical simulation 250 times supercritical perform
 ed at an Ekman number equal to 10-7.
LOCATION:Seminar Room 1\, Newton Institute
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