Magnetic core field anomalies in the non-axial field during the last 3300 years: approach with an equivalent monopole source

PABLO RIVERA PÉREZ ^1* F. Javier Pavón-Carrasco ¹ Angelo De Santis ² Saioa A. Campuzano ¹ Gianfranco Cianchini ² M.Luisa Osete ¹

• ¹ Complutense University of Madrid, Madrid, Spain
• ² National Institute of Geophysics and Volcanology (INGV), Roma, Lazio, Italy

The continuous update of the archeomagnetic database spanning the last 3000 years has facilitated the refinement of geomagnetic field models, unveiling the presence of significant non-dipolar anomalies before instrumental measurements. Within the Holocene epoch, two anomalies have become notably well-defined. The South Atlantic Anomaly (SAA), characterized by low geomagnetic intensities in the South Atlantic region almost during the last millennium, stands out as the most significant present-day anomaly. In addition, the Levantine Iron Age Anomaly (LIAA) has been defined as a geomagnetic spike characterized by abnormally high intensities affecting Levant and Europe during the first half of the first millennium BCE. We analyze the spatial and temporal evolution of these anomalies using a straightforward model. Our approach involves fitting the non-axial field responsible for defining these anomalies with an equivalent monopole source situated in the proximity to the core-mantle boundary. Results indicate that the movement of the monopoles associated with SAA and LIAA seems to align with regions of the lower mantle characterized by low shear velocity, particularly the edges of the African Large Low Shear Velocity Province (LLSVP), suggesting a correlation with lower mantle heterogeneities.