BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Invited speaker: Stable stratification in planetary interiors: con
 straints coming from the magnetic field - Thomas Gastine (Institut de Phys
 ique du Globe de Paris)
DTSTART:20221201T100000Z
DTEND:20221201T104500Z
UID:TALK192125@talks.cam.ac.uk
DESCRIPTION:Convective motions which develop in the Earth liquid outer cor
 e or in the deep interior of the gas giants planets are thought to be the 
 main driver of planetary magnetic fields via dynamo action. These electric
 ally-conducting &nbsp\;fluid regions are nevertheless not necessarily enti
 rely convecting. In the case of the Earth core\, corroborating evidences c
 oming from seismic studies\, mineral physics and thermal evolution models 
 suggest the existence of a stably-stratified layer underneath the core&nda
 sh\;mantle boundary. Such a layer could find its physical origination eith
 er in compositional stratification due to the accumulation of light elemen
 ts at the top or the core or in thermal stratification due to the heat flu
 x becoming locally sub-adiabatic. In the case of gas giant planets\, const
 raints coming from gravity measurements\, ab-initio calculations and ring-
 seismology (in the case of Saturn) suggest an intricate internal structure
  with fluid regions where helium would segregate from hydrogen\, forming a
  compositionally-stratified layer. Such stable layers can have crucial dyn
 amical impacts on dynamo action. Because of the inhibition of the convecti
 ve motions\, a stable layer is expected to primarily act as a low-pass fil
 ter on the magnetic field\, smoothing out the rapidly-varying and small-sc
 ale features by skin effect. This defines a magnetic constraint on the pro
 perties of stably-stratified layers in planetary &nbsp\;interiors. During 
 this talk\, I will present global numerical dynamo models of the geodynamo
  and of the gas giants planets which incorporate stably-stratified layers 
 to quantify their impact on the magnetic field generation. ~ &nbsp\;&nbsp\
 ;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nb
 sp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;
 &nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbs
 p\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&
 nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp
 \;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;&nbsp\;
LOCATION:Seminar Room 1\, Newton Institute
END:VEVENT
END:VCALENDAR