We are using numerical dynamos driven by non-uniform heat flux at the core-mantle boundary to explore the links between paleomagnetic field structure, paleomagnetic reversal frequency, core evolution, and mantle convection through Phanerozoic time.
We calculate magnetic polarity reversal sequences and time average magnetic field structures using a dynamo driven by a reconstruction of mantle convection with plate motions that produces time variable core-mantle boundary (CMB) heat flux and an irregular evolution of the core.
Present-day values of the dynamo control parameters are tuned to match Geomagnetic Polarity Time Scale (GPTS) reversal statistics for 0-5 Ma, and the time dependences of the dynamo control parameters are determined from the thermal evolution of the core, including time variability of CMB heat flow, inner core size, inner core chemical buoyancy flux, and rotation rate.
Our mantle convection driven dynamo shows large reversal rate fluctuations including stable polarity at 275 Ma and 475 Ma and frequent reversals at other times. This dynamo also produces departures from geocentric axial dipole symmetry during the time of supercontinent Pangaea and a heterogeneous growth history of the inner core.
Johnson, C., Constable C.G., 1995. The time-averaged geomagnetic field as recorded
by lava flows over the last 5 Ma, Geophys. J. Int., 122, 489-519.
Olson, P., Deguen, R., Hinnov, L., Zhong, S. , 2012. Controls on geomagnetic
reversals and core evolution by mantle convection in the Phanerozoic,
Phys. Earth Planet. Inter. (in press).
Valet, J., Meynadier, L., Guyodo, Y., 2005. Geomagnetic field strength and reversal rate
over the past 2 million years, Nature 435, 802-805.
Zhang N., Zhong, S. J., 2011. Heat fluxes at the Earth's surface and core-mantle boundary
since Pangea formation and their implications for the geomagnetic superchrons,
Earth Planet. Sci. Lett. 306, 205-216.