de Oliveira Wellington P, Hartmann Gelvam A, Terra-Nova Filipe, Pasqualon Natália G, Savian Jairo F, Lima Evandro F, da Luz Fernando R, Trindade Ricardo I F
Instituto de Geociências, Universidade Estadual de Campinas, Campinas, Brazil.
Nantes Université, Univ Angers, Le Mans Université, CNRS, Laboratoire de Planétologie et Géosciences, Nantes, France.
Nat Commun. 2024 Nov 1;15(1):9447. doi: 10.1038/s41467-024-53688-2.
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°30'S, 29°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.
地球磁场呈现出主要的偶极形态。尽管如此，如今明显存在与偶极的显著偏差，尤其是南大西洋异常区（SAA），其特征是场强异常低且方向变化大，削弱了磁场的屏蔽作用。为了评估类似南大西洋异常区的特征在数百万年时间尺度上的持续性，我们将来自特林达迪岛（南纬20°30′，西经29°22′）的古地磁数据与过去1000万年的古地磁场长期变化（PSV）评估相结合。我们采用合成模型来探究核幔边界处磁通量斑块的位置和强度如何影响长期磁场行为。在此，我们展示的结果揭示了南大西洋的异常场特征，并且大西洋 - 太平洋半球不对称性是持久特征，这可能与内核不均匀性对古地磁场长期变化的自下而上控制有关，但在长时间范围内也受到地幔异常的影响。
