Video: Magnetic field update
This animation shows changes in Earth's magnetic field from January to June 2014 as measured by ESA's Swarm trio of satellites.
The magnetic field protects us from cosmic radiation and charged particles that bombard Earth, but it is in a permanent state of flux. Magnetic north wanders, and every few hundred thousand years the polarity flips so that a compass would point south instead of north. Moreover, the strength of the magnetic field constantly changes – and it is currently showing signs of significant weakening.
The field is particularly weak over the South Atlantic Ocean – known as the South Atlantic Anomaly. This weak field has indirectly caused many temporary satellite 'hiccups' (called Single Event Upsets) as the satellites are exposed to strong radiation over this area.