Global Geomagnetic Models

Declination (magnetic variation) in region of north pole at 2020.0 from the World Magnetic Model . Red - positive (east), blue - negative (west), green - zero. Contour interval is 5°. (Click to enlarge).

The shape and strength of the Earth's magnetic field is not simple nor easy to describe exactly. It has a complex form, originating from sources in the Earth's core, the Earth's crust and in the ionosphere-magnetosphere system, each of which changes continuously over time. Geophysicists have to rely on mathematical models to compute the strength and direction of the magnetic field at any point on or near the surface of the Earth. Given that the field changes continuously, we must also make forecasts so that a model remains useful for some time after it is produced.

At BGS we produce a series of magnetic field models for both practical and scientific purposes. Each of the models listed below (WMM, IGRF, BGGM and MEME) describes the magnetic field to different levels of accuracy, mainly through different update schedules and incorporation of model parameters that represent more of the crustal field and the external field. Research is ongoing to improve our ability to forecast the change of the magnetic field over time (known as secular variation) and to use new mathematical techniques to improve the models.

These pages describe scientific and technical details of our modelling and research and provide access to online calculators and maps.

• World Magnetic Model (WMM)

• International Geomagnetic Reference Field (IGRF)

• BGS Global Magnetic Model (BGGM)

• Model of the Earth's Magnetic Environment (MEME)

• Improving our predictions of Secular Variation (SV)