There are different approaches to define the behaviour of the Earth's magnetic field in the recent past. The classical treatment consists of determining the so-called Secular Variation Curves (valid for regions of about 600 km in diameter) which are constructed from averaged moving windows (Stenberg et al., 1990; Le Golf et al., 1992), variable moving windows (Le Golf et al., 2002), methods based on Bayesian statistics (Lanos, 2001), or new methods based on the L1 norm (Thébault and Gallet, 2010).

Another approach is to analytically represent the spatial and temporal behaviour of the geomagnetic field from archaeomagnetic data by means of harmonic analysis. On a global scale this representation has been tested during the last decade (e.g. Korte et al., 2009). However, in Europe, where the point density is higher than anywhere else on the globe, and is expected to increase considerably over the next two years due to the existence of the AARCH project, the representation of smaller scale field features is possible through regional modelling, such as Spherical Cap Harmonic Analysis or SCHA (Haines, 1985).

The Paleomagnetism group at the Complutense University of Madrid has generated the first geomagnetic field models for the European region, North Africa and West Asia from archaeomagnetic data and lake sediments. One example is the SCHA.DIF.3k model that allows us to know the components of the geomagnetic field in the European region for the last 3000 years (Fig.1).



Since then, the group has continued developing this branch of the geomagnetic field study by publishing several models, both regional (SCHA.DIF.8k) and global (SHA.DIF.14k, SHAWQ2k, SHAWQIron-Age). For more information on these models: link.