For three years, satellites have been mapping the upper part of the Earth’s magnetic field and collecting data on a Magnetic Anomaly in Africa. The result is the highest resolution map of the Earth’s crust seen to date. This ‘lithospheric magnetic field’ is very weak and difficult to detect from space, but Swarm satellites have made it possible. “By combining Swarm measurements with historical data from the German CHAMP satellite, and using a new modeling technique, it was possible to extract the tiny magnetic signals of crustal magnetization with unprecedented accuracy,” professor Nils Olsen from the Technical University of Denmark (UTA) commented.
The majority of the Earth’s magnetic field in generated at depths greater than 3000 km by the movement of molten iron into the outer core. The remainder is due, in part, to electrical currents in space surrounding the Earth; and is also caused by magnetized rocks in the upper lithosphere.
The new map shows detailed variations in the field caused by geological structures in Earth’s crust. In the Central African Republic, centered around the city of Bangui, the magnetic field is significantly sharper and stronger than surrounding areas. While the cause of this remains unknown, scientists speculate it could be the result of meteorite impact there 540 million years ago.
The new map also answers questions about the Earth’s magnetic field flipping polarity many times over the millennia. The magnetic field is in a permanent state of flux, and every few hundred thousand years the polarity flips. When new crust is generated through volcanic activity, iron-rich minerals in the magma are oriented towards magnetic north. The solidified minerals form “stripes” on the seafloor, providing a record of Earth’s magnetic history.
“Understanding the crust of our home planet is no easy feat,” ESA’s Swarm mission manager, Rune Floberhagen, notes. “Measurements from space have great value as they offer a sharp global view on the magnetic structure of our planet’s rigid outer shell.”
Source: Science Daily