Filling Critical Archeomagnetic Data Gaps

The Earths magnetic field protects our planet along with its inhabitants and their technical infrastructure from cosmic radiation. However, during the last 200 years systematic observations have shown that the strength of our protective shield has been continuously decreasing. The reasons for that can be found in the Earths Outer core, the so-called geodynamo. The geomagnetic field is generated there by convection currents of mainly molten iron. Turbulent changes of flow patterns can actually cause magnetic field reversals. However, a look back into the more distant past is essential in order to better assess the current decline of the geomagnetic field strength. An opportunity therefore is offered by materials containing ferrous minerals. These materials, like for instance archeological artifacts, store the ambient magnetic field upon cooling from high temperatures above 500C. Consequently, burnt clays like potsherds are the ideal candidates for reconstructing the ancient geomagnetic (archeomagnetic) field in the laboratory with highly sensitive measuring instruments. The target of this project is the investigation of two extraordinarily interesting historical periods, when the archeomagnetic field strength was twice as high as today. High field strengths along with rapid temporal changes are reported for the Near East during the Bronze to Iron Age transition, while for the Early Medieval Times high archeomagnetic intensities have been measured within Western Europe. However, in Central Europe these anomalies are still hardly constrained. Therefore, a new archeomagnetic measurement campaign in collaboration with an international archeological team will be conducted. Suitable archeological finds will be examined in the laboratories of the institutions Geosphere Austria and University Leoben in order to determine spatial and temporal changes of the geomagnetic field within the above mentioned periods. The modelling of the global magnetic field will provide indications of the underlying processes in the geodynamo. Furthermore, more reliable reference curves for the archeomagentic dating technique will be obtained for Central Europe.