Archeomagnetic results from Spain

Abstract

1 p.

International audience

A first secular variation (SV) curve for the Iberian Peninsula was computed by hierarchical Bayesian method using a total of 134 archaeomagnetic directions with ages ranging from 775 BC to 1959 A.D. A general agreement is observed between the Iberian curve and the French and German SV curves, excepted between the 11th and 14th centuries. The analysis of these three reference curves indicates that SV in western Europe is characterized by three major directional changes at 125, 200, and 1350 A.D. It is suggested that these cusps are regional features of the geomagnetic field. Archeointensity studies were also conducted on 24 Spanish archeomagnetic sites (220 AD to 1959 AD). Intensity data were obtained using the original Thellier method with anisotropy and cooling rates corrections. Our new 24 data, together with 62 previously published results, were used to recover, by Bayesian modelling, the geomagnetic field intensity evolution over the past two millennia for western Europe. Our results indicate that the geomagnetic intensity remains more or less constant between the 1st and 4th centuries, and between the 13th and 15th centuries, whereas an important decrease occurs during the last 5 centuries. The evolution of the Earth's magnetic field intensity during High Middle Ages remains uncertain. The available geomagnetic global models predict reasonably well our data.