Long-term persistency of a strong non-dipole field in the South Atlantic

Earth's magnetic field exhibits a dominant dipole morphology. Notwithstanding, significant deviations from the dipole are evident today, particularly the South Atlantic Anomaly (SAA), characterized by anomalously low-field intensity and high directional variability, diminishing the field's shielding effect. To assess the persistence of SAA-like features over multimillion-year scales, we combine paleomagnetic data from Trindade Island (20 degrees 30'S, 29 degrees 22'W) with an evaluation of paleosecular variation (PSV) over the past 10 Myr. We employ synthetic models to explore how the position and intensity of magnetic flux patches at the core-mantle boundary can influence the long-term field behavior. Here we present results that reveal anomalous field signatures in the South Atlantic and the Atlantic-Pacific hemispheric asymmetries are enduring features, likely linked to a bottom-up control of PSV by the inner core's heterogeneities but with contributions from mantle anomalies in the long-time range. This study provides evidence of a long-term anomalous behavior of the geomagnetic field in the South Atlantic from paleodirectional data of Trindade Island. Furthermore, field models suggest the persistence of anomalous features for the past 10 Myr.