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SUMMARY:A topsy-turvy world: dynamo generation by top-down solidification 
 of planetesimals - Dr. Jerome Neufeld (DAMTP\, Cambridge)
DTSTART:20200211T130000Z
DTEND:20200211T140000Z
UID:TALK133570@talks.cam.ac.uk
CONTACT:Chris Hamilton
DESCRIPTION:Modern paleomagnetic measurements of asteroid fragments indica
 te that magnetic field generation was not uncommon in the early solar syst
 em\, with many smaller bodies exhibiting strong magnetic fields lasting 10
 -20 Ma.  For smaller planetesimals\, the mode of solidification is from th
 e top down\, in contrast to our current experience of magnetic field gener
 ation on Earth.  Since thermal convection is likely short lived\, solidifi
 cation from the top down presents a challenge to current models of magneti
 c field generation.  Here we discuss the possibility of magnetic field gen
 eration through stirring driven by the episodic delimitation of a viscous 
 iron crust\, both in the limit of a pure iron planetesimal and where sulph
 ur impurities are present.
LOCATION:MR21\, Centre for Mathematical Sciences\, Wilberforce Road\, Camb
 ridge
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