Britannica Sources used in this answer

How does the freezing of Earth’s liquid core release energy for the geomagnetic dynamo?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

geomagnetic field The magnetic field of a bar magnet has a simple configuration known as a dipole field. Close to Earth's surface this field is a reasonable approximation of the actual field.

The geomagnetic dynamo is powered by fluid motion within Earth’s outer core, which acts as an electrically conducting medium. While it was once believed that radioactive decay provided the necessary heat to drive this motion, current research indicates that the freezing of the liquid core is a more significant energy source.1

Earth’s core consists of a solid iron inner sphere surrounded by a liquid outer core. Over time, the inner surface of this liquid core freezes onto the solid inner core. This phase transition releases latent heat, which warms the surrounding regions.1

This process creates a radial temperature distribution that decreases toward the surface. When this heat is generated faster than it can be removed by conduction, it triggers convection. During convection, bubbles of hot fluid rise toward cooler regions, transporting thermal energy. This fluid motion, influenced by the Coriolis force, twists and amplifies the magnetic field, maintaining the self-sustaining dynamo that generates Earth's magnetic field.1