Effect of the Heat Source Distribution in the Earth's Core on the Stability of Geodynamo

We investigate the effect of the heat source distribution on the behavior of the magnetohydrodynamic (MHD) dynamo action. We consider three models in which the ratio of the heat flow at the inner core boundary to that extracted away from the core to the mantle varies from 0%, 50% to 100%. The most frequently studied geodynamo model with a temperature difference between the upper and lower boundaries corresponds to the 100% case. An important parameter closely related with the thermal condition is the Rayleigh number, which is defined as it indicates the amount of heat flow taken away from the core surface, and therefore, we performed a parameter study by changing the Rayleigh number as another control parameter. The results suggest that both the Rayleigh number and the heat source distribution influence the stability of the magnetic field. We also performed the case without the inner core to investigate the geometrical effect of the inner core on the dynamo action. The representative results of the simulations are summarized in this report.