The Earth's magnetic field is generated by electric currents in the molten outer core, and affected by local variations in the mantle and crust. Above the surface, fluctuations of magnetospheric and ionospheric origin are increasingly significant and are affected by the solar wind.
The magnetic field protects us from cosmic radiation and the atmosphere from erosion by the solar wind. We navigate the planet using the compass, and have done so for centuries. The direction of magnetic north does not correspond to the geographic north, and a correction (magnetic declination) is required to convert from one to the other.
The direction of the magnetic field vector varies with position and time (the Earth's magnetic poles shift over time). Scientists around the world are studying this variation to improve our understanding of it, and ability to predict changes in future.
The World Magnetic Model (WMM) is scientific software that calculates magnetic declination, inclination, and intensity at a particular time and position. It is based on data measured by dedicated satellites as part of the SWARM mission and by the ground based observatories of the INTERMAGNET network. It is relied upon throughout the world for navigation, mineral exploration, atmospheric and space science, and is installed on billions of devices in some form.
We provide a RESTful API to the latest version of the WMM so that developers in industry and academia can access the functionality of the model without needing to install legacy software. The free API is limited to 1000 calls per day and is ideal for proof-of-concept activities. Its ease of use is demonstrated below.
We are validating the API calculations against published experimental data and benchmarking against other models.
Results and analyses are available for review on our online repository
The following is an animation of the magnetic declination measured by the SWARM-A satellite over the course of a day. A comparison is made with values predicted by the WMM model accessed through Amentum's API.