• ISSN 2097-1893
  • CN 10-1855/P

南大西洋地磁异常区的长期变化研究进展

Review of secular variation studies in the South Atlantic Anomaly

  • 摘要: 南大西洋地磁异常区(South Atlantic Anomaly, SAA)是如今地球磁场最显著的结构特征之一,区域内存在磁场强度弱、辐射高、高能粒子通量增加等特点,并且该区域在近百年来持续进行向西漂移和面积扩张. SAA的长期变化影响了近地空间环境,反映了地球深部动力学特征,是研究地球磁场发电机的重要窗口. 近年来地磁场表现出偶极子能量不断减弱、非偶极子能量正在增加的趋势,SAA表现出比历史时期更迅速的变化速度,各向异性有所增加,并出现了次级异常中心,这些新的变化说明SAA的演化可能进入了新的时期,引发人们对SAA长期演化规律以及未来演化趋势的关注和探讨. 本文将结合古地磁与现代地磁模型研究结果,对SAA在过去、现在、未来的演化特征的研究结果进行总结,并对SAA的成因进行综述分析.

     

    Abstract: The South Atlantic Anomaly (SAA) is one of the most remarkable structural features of the Earth's magnetic field. The region is characterized by weak magnetic field intensity. Because of this weakening, particles within the inner radiation belt can mirror at lower altitudes, consequently increasing the local particle flux. Over centuries, the SAA has displayed notable secular variation (SV) characteristics, with a consistent decline in strength, expansion in area, and an overall westward drift. Both paleomagnetic and modern magnetic data indicate that SAA is currently undergoing rapid changes, with a rapid expansion in area and a rapid decreasing in intensity. These changes are coinciding with an increasing field asymmetry. Recent observations suggest that the evolution of SAA has become increasingly anisotropic, showing two magnetic intensity minima. This may indicate that the evolution of SAA has entered a new stage, which has aroused people's attention and discussion on the long-term evolution and future of SAA. The manifestation of the SAA on the Earth’s surface corresponds to the response of an inverse flux path at the core-mantle boundary (CMB) to the radial component of the geomagnetic field, positioned approximately beneath the South Atlantic Ocean. Consequently, studying the SV of SAA can understand the details of the Earth's internal dynamics. Moreover, these SV scenarios provide some speculative predictions for the SAA. The evolutionary details of SAA not only serve as a reference for future trends but also imposes additional constraints on Earth's core dynamic model, rendering it a compelling subject for scholarly inquiry. In this paper, we review the results of paleomagnetic and modern geomagnetic models concerning the past, present, and future evolution of the SAA, while also summarizing advancements in understanding the origin of this anomaly.

     

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