The new face of the Earth's magnetic field: what did we learn from World Magnetic Model 2015 and the recently launched Swarm satellite mission?

Arnaud Chulliat (1,2), Patrick Alken (1,2), Manoj Nair (1,2), Adam Woods (1,2), Brian Meyer (1,2)

Abstract
The World Magnetic Model (WMM) is a data-based, spherical harmonic model of the Earth’s magnetic field at or near the Earth’s surface. It is developed jointly by NGDC and the British Geological Survey, and is a joint product of the United States’ National Geospatial-Intelligence Agency and the United Kingdom’s Defence Geographic Centre. The WMM is the standard navigation product of the Department of Defense and NATO; it is used in every ship, aircraft and submarine. It is also widely used by NOAA, FAA, USGS and the commercial sector for applications ranging from spacecraft attitude control to providing headings in smartphones. The WMM needs to be updated every five years as the Earth’s magnetic field slowly changes in time due to flows within the Earth’s outer core, and this change is currently unpredictable beyond a few years. The latest update, WMM2015, was released in December 2014 and is valid until 2020. It is mostly based on high-precision geomagnetic data from the European Space Agency’s Swarm satellite mission, launched in November 2013. It reveals a continuing drift of the North magnetic pole toward Siberia, albeit at a slightly slower speed, and a further deepening of the South Atlantic Magnetic Anomaly, a large area centered on Southern Brazil where the intensity of the magnetic field is twice to three times lower than in North America. We’ll report on the most recent changes of the Earth’s magnetic field as described by WMM 2015 and other recent, Swarm-derived geomagnetic models, and discuss their origin as well as possible implications for WMM users.