Lost in migration: Earth's magnetic field overdue a flip | Reuters

Scientists, who have known for some time the magnetic field has a tendency to flip, have made advances in recent years in understanding why and how it happens.

The field is generated by convection currents that churn in the molten iron of the planet's outer core. Other factors, such as ocean currents and magnetic rocks in the earth's crust also contribute.
The Swarm mission will pull all these elements together to improve computer models used to predict how the magnetic field will move and how fast it could weaken.
Ciaran Beggan, a geomagnetic specialist at the British Geological Survey in Edinburgh, said studies have also refined our understanding of how the field reverses.
They have focused on lava flows. When these cool and form crystals the atoms in iron-rich molten rock align under the influence of the magnetic field, providing a geological memory of the earth's field.