Superchron cycles driven by variable core heat flow

A numerical dynamo with time variable core heat flow and inner core growth rate links the thermal state of the Earth's core to the long term trends in the Geomagnetic Polarity Time Scale (GPTS). Increasing core heat flow over 100 Myr drives the numerical dynamo from a superchron state to reversing behavior, whereas a similar decrease in core heat flow produces a decrease in reversal frequency, driving the dynamo back into a superchron. The polarity sequence, including more than 400 reversals and two superchrons, compares favorably with the GPTS, as does the dynamo frequency spectrum. We find that core heat flow is positively correlated with polarity reversal frequency, dipole variability, and the relative strength of the non-dipole field. Our results imply that changes in geomagnetic reversal frequency can be attributed to long period fluctuations in core heat flow, and suggest heat flow minima during superchrons and a maximum near the present-day. Citation: Driscoll, P., and P. Olson (2011), Superchron cycles driven by variable core heat flow, Geophys. Res. Lett., 38, L09304, doi: 10.1029/2011GL046808.