Magnetic core field anomalies in the non-axial field: approach with a monopole.

The continuous update of the archaeomagnetic database spanning the last 3000 years has facilitated the refinement of geomagnetic models, unveiling the presence of non-dipolar anomalies previous to 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, stands out as the most significant present-day anomaly. Its origin and evolution before instrumental records is still under debate and has been suggested as a possible persistent or recurrent feature of the field. 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 approach to the analysis of these anomalies with a simple model, using a monopolar source to locally fit the non-axial field around these anomalies. The movement of the monopoles associated with SAA and LIAA seems to align with regions of the 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.