What process generates most of Earth’s large-scale magnetic field?

The geodynamo is the process that generates most of Earth’s large-scale magnetic field.

It operates in the planet’s electrically conducting outer core, which is composed primarily of molten iron and nickel. Convection caused by heat loss and the growth of the solid inner core drives moving fluid, while Earth’s rotation organizes that motion through the Coriolis effect. The resulting electric currents create a magnetic field.

Earth’s field is approximately dipolar at the surface, although it is not perfectly aligned with the geographic axis and changes over time. The field deflects much of the charged-particle flow from the Sun and helps produce auroras when some particles enter near the poles.

The geodynamo is not the same as a permanent magnet hidden inside Earth. The core is far too hot for ordinary ferromagnetism to maintain the field. Scientists study the process using observations, laboratory experiments, computer simulations, and evidence preserved in magnetic minerals.