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SUMMARY:Early Earth Dynamos (Invited speaker) - Andrew  Jackson (ETH Züri
 ch)
DTSTART:20220912T101500Z
DTEND:20220912T110000Z
UID:TALK177467@talks.cam.ac.uk
DESCRIPTION:The Earth&rsquo\;s magnetic field has existed for at least 4 G
 yr. Before the onset of crystallisation of the solid innercore\, and for p
 ossibly as much as 90% of Earth history\, the relevant geometry was that o
 f a full sphere. Numericalstudies of the geodynamo in a full sphere are th
 us critical for understanding the paleomagnetic field.However\, direct num
 erical simulation of the dynamo problem in a whole sphere have been rare\,
 partially due to the difficulty of proper treatment of the singularity at 
 the sphere centre. Using a fullyspectral method with basis functions which
  are smooth everywhere\, we run a series of numericalsimulations to invest
 igate dynamos in a whole sphere. For various Ekman numbers E\, measuring t
 heeffect of viscosity compared to the Coriolis force\, the dynamo regime d
 ependence on the Rayleighnumber Ra (measuring thermal forcing) and the mag
 netic Prandtl number Pm (controlling electricalconductivity) was determine
 d\, and we find it to be different from that of dynamos operating in asphe
 rical shell.&nbsp\;\nWith Jiawen Luo and Philippe Marti
LOCATION:Seminar Room 1\, Newton Institute
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