BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Chemical convection and stratification at the top of the Earth's o
 uter core - Matthieu Bouffard\, Max Planck Institute for Solar System Rese
 arch
DTSTART:20180219T130000Z
DTEND:20180219T140000Z
UID:TALK99682@talks.cam.ac.uk
CONTACT:Prof. John R. Taylor
DESCRIPTION:The outer core of the Earth is a liquid layer made of iron\, p
 lus a small fraction of nickel and lighter elements (O/S/Si...). In this l
 ayer\, the combination of thermal and compositional effects drives convect
 ive currents which generate the magnetic field of the Earth by dynamo acti
 on. However\, vigorous convection may not take place in the entire outer c
 ore since seismic and magnetic observations suggest that its top 60-300km 
 is stably stratified. This stratified layer at the top of the core could h
 ave important consequences for the terrestrial dynamo\, the dynamics and e
 volution of the core\, but its origin remains enigmatic. Several scenarios
  have been proposed to explain the formation of such a layer. One possibil
 ity is that light chemical plumes and "blobs" emitted at the bottom of the
  outer core by the crystallization of the inner core could accumulate belo
 w the top of the core\, gradually forming a chemically stratified layer. T
 he plausibility of this scenario can be assessed using a new code based on
  a particle-in-cell method I developed during my PhD\, which allows to dea
 l with the low value of the compositional molecular diffusivity (the chemi
 cal Prandtl number is large)\; an ingredient neglected in previous simulat
 ions. In this seminar\, I will present the results of recent numerical sim
 ulations of rotating chemical convection in a spherical shell. I will desc
 ribe the general characteristics of rotating convection at large chemical 
 Prandtl number and will show that a chemically stratified layer forms at t
 he top of the shell in all simulations. I will then discuss the extrapolat
 ion to the Earth's outer core.
LOCATION:MR5\, Centre for Mathematical Sciences
END:VEVENT
END:VCALENDAR