CSEDI: Collaborative Research: Paleomagnetism, the Geodynamo and Core-Mantle Interactions

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Bloxham Constable It is proposed to undertake a collaborative study of mantle influences on the geodynamo, combining geodynamics, geodynamo modeling and paleomagnetism, focusing on three timescales. First, by looking at the last 5 million years the long timescale behavior of the dynamo over a period for which both the time averaged field and the paleosecular variation can be determined paleomagnetically will be examined. Furthermore, on this timescale the lowermost mantle is essentially unchanged from that which is imaged using seismic tomography, so modern tomographic images of the mantle can be used. Second, changes in reversal frequency, concentrating on the period from the Cretaceous Normal Superchron to the present day will be examined, including the effect of plume formation at the base of the mantle on the occurrence of reverse flux patches in the magnetic field. Third, preliminary investigations will be conducted on the very long-term changes in the magnetic field occurring over timescales of several hundred million years. This work will involve a statistical re-analysis of the available paleomagnetic measurements to assess what kinds of geodynamo experiments will be relevant to understanding such long-term changes. The dynamo modeling and geodynamical modeling will be performed at Harvard; the paleomagnetic aspects of the proposal, involving data compilation, analysis, and field modeling will be performed at Scripps Institution of Oceanography. The work will be coordinated between the two institutions primarily by electronic means, supplemented by visits and short-term exchange of students between the institutions.