Simulations of the Earth's magnetic field and length-of-day variations

The Earth's core, mostly made of liquid iron, is stirred by convection which leads to our magnetic field.
These movements can also transport angular momentum and exchange it with the solid mantle, inducing variations in the length of day.
I will present recent simulations of the dynamics of the core and of the magnetic field, and the implications for the both the core-mantle boundary and the length-of-day variations.