You might not see it or even realize it, but Earth's magnetic field is vital in protecting life on the planet from the constant onslaught of harmful cosmic radiation and charged particles from the solar wind. Extending out from Earth's core like an invisible cocoon, the planet's geomagnetic field is also informed by the lithosphere (its crust and upper mantle). The layer is made up of magnetized rocks that produce a weak field that is difficult to detect, meaning that the exact details of Earth's magnetic field as a whole is probably much more complex than we might imagine.
That's what researchers over at the European Space Agency (ESA) are revealing in a recent three-dimensional map of the Earth's "lithospheric magnetic field", created using data from a trio of satellites collectively known as Swarm. The result is a map that does not look uniform at all, offering new clues and more questions about how our lithosphere's magnetic field has changed over the course of geological history. As one of the team's scientists, Nils Olsen from the Technical University of Denmark, explains, this is the highest resolution map of its kind:
By combining Swarm measurements with historical data from the German CHAMP [Challenging Minisatellite Payload] satellite, and using a new modelling technique, it was possible to extract the tiny magnetic signals of crustal magnetization.
This colour-coded model shows areas of weak magnetic activity shaded in blue, while areas of high magnetic activity are shown in red. One of the mysteries opened up by this new map is an area of sharp magnetic intensity around the city of Bangui in the Central African Republic, as seen in the video. Scientists theorize that it may be due to a meteorite crashing here over 540 million years ago.
The earth's ever-changing crust -- altered through volcanic activity on land and underwater -- also provides insight into the history of the planet's dynamic magnetic field as minerals in cooling magma organize themselves according to a magnetic north that can shift over time, creating 'stripes' along the ocean floor that can be seen in the model. Dhananjay Ravat from the University of Kentucky explains:
These magnetic stripes are evidence of pole reversals and analyzing the magnetic imprints of the ocean floor allows the reconstruction of past core field changes. They also help to investigate tectonic plate motions. The new map defines magnetic field features down to about 250 km and will help investigate geology and temperatures in Earth’s lithosphere.
Another mystery that the scientists are pondering is why the Earth's magnetic field is weakening in certain regions. Scientists believe that Swarm's data will help us better understand natural processes that occur inside the planet, as well as conditions in outer space that are influenced by solar activity. In any case, there's plenty to unravel as the mission continues to observe and map Earth's complex and ever-shifting magnetic field. Read more over at ESA's Swarm.