[S-CG42] Frontier of Understanding Earth's Interior and Dynamics

[SCG42-04] On the long-term evolution of the geomagnetic field: A link between geodynamics and planetary habitability

★Invited Papers

*Takashi Nakagawa^1,2 (1.Kobe University, 2.Hiroshima University)

Keywords:Paleomagnetism, Core-mantle dynamics, Habitability

Here, I introduce a brief review on how the long-term evolution of the geomagnetic field plays a key role in dynamics and evolution of Earth’s deep interior. For revealing the long-term variations of the geomagnetic field, the measurement of paleointensity is used, but it is quite controversial for giving various interpretations on dynamics and evolution of Earth’s deep interior by using the paleomagnetism data only. In order to provide a better interpretation, the geodynamics approach is essential because the long-term evolution might be controlled by the plate tectonics driven by the mantle convection, which is a coupled core-mantle evolution model in mantle dynamics simulations or semi-analytical computations of parameterized mantle dynamics. For evaluating the magnetic evolution, there are two approaches – 1. Estimate of heat by the magnetic dissipation and 2. Evaluation of the convective power. Both approaches give similar results and interpretations, but the convective power approach gives a better interpretation on the magnetic evolution, because this approach may use all the required energy sources on generation of the magnetic field. For understanding the current constraints on paleomagnetic data, the heat flow across the core-mantle boundary is the most important quantity, ranging from around 10 to 15 TW at the present-day in geodynamics modeling. An additional important quantity is the thermal conductivity of Earth’s core because this quantity strongly affects the convective power of Earth’s core, which should be less than around 110 W/m/K to maintain the magnetic field generation before the inner core nucleation got started. The long-term evolution of the geomagnetic field also plays a significant role in planetary habitability because the geomagnetic field can work for shielding us from the harmful solar radiation. I also discuss this aspect in presentation.