Collaborative Research: Archeomagnetism of southern Africa and dynamo modeling: Testing the hypothesis of South Atlantic Anomaly-Large Low Shear Velocity Province Agency

合作研究：南部非洲的考古地磁学和发电机建模：检验南大西洋异常-大低切变速度省机构的假设

• 批准号: 2201460
• 负责人: John Tarduno
• 金额: $ 49.66万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2201460&HistoricalAwards=false
• 关键词: Collaborative; Research; Archeomagnetism; southern; Africa

Earth’s dipole magnetic field has been rapidly decreasing in strength, by ∼9% over the past 160 years, with the decline linked to a broad swath of low field intensity in the Southern Hemisphere known as the South Atlantic Anomaly. When extrapolated to Earth’s deep interior, to the boundary between the liquid core and overlying solid mantle, this weak surface field appears as prominent patches of reversed polarity beneath South Africa and Patagonia. This pattern, together with the rapidly decreasing field strength, has led to hotly debated speculation that Earth is in the early stages of a geomagnetic polarity reversal. Principal limitations in this debate have been a lack of data for the last 1500 years from key regions in the Southern Hemisphere and theoretical understanding of deep Earth controls on magnetic fields. To address these limitations, this project will refine the archeomagnetic record of the southern Hemisphere, develop numerical simulations to explore the affect the deep Earth has on magnetic fields, and integrate these two components to explore whether the unusual mantle beneath South Africa and Patagonia (the African Low Shear Velocity Province) places a first-order control on the character of the South Atlantic Anomaly. This project will foster international collaboration with archeologists from South Africa, Botswana, and Zimbabwe, develop a revised geodynamo code that will be made available to the community, and support of graduate and undergraduate students who will receive a broad training in the field, experimental rock and paleomagnetism, and geophysical modeling.This project will support a collaborative study that will bring together workers in disparate disciplines and subdisciplines to further refine the archeomagnetic record and more directly test the efficacy of Low Shear Velocity Province control on the character of the geomagnetic field. Specifically, the research team will: (i) conduct field studies including field surveys and collection materials with the goal of refining the Iron Age archeomagnetic record with potential application to both deep Earth and to archeological problems; (ii) conduct rock magnetic, analytical microscopy, and paleomagnetic analyses and processing of field magnetic survey data to define ambient magnetic fields of the collection sites, magnetic carriers in the collected archeological artifacts, and ancient recordings of direction and intensity with the goal of testing primary hypothesis of the proposed work; and (iii) use numerical dynamo simulations to investigate whether the African Large Low Shear Velocity Province can locally defect core flow, drive the magnetic Reynolds number toward unity, favoring magnetic diffusion and flux expulsion, and thus place first-order controls on geomagnetic observations made at Earth’s surface.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在过去的160年中，地球的偶极磁场的强度一直在迅速降低，约为9％，下降与南半球的低场强度相关的较大特警被称为南大西洋异常。当推断到地球深内部，到液态核心和上覆的固体地幔之间的边界时，这种薄弱的地表场似乎是南非和巴塔哥尼亚下方的显着极性斑块。这种模式以及迅速降低的田间强度，导致人们争论的猜测是，地球处于地磁极性的早期阶段。在过去的1500年中，南半球的主要区域以及对磁场深地球控制的理论理解的过去1500年中，主要局限性缺乏数据。 To address these limitations, this project will refine the archeomagnetic record of the Southern Hemisphere, Develop numerical simulations to explore the affect the deep Earth has on magnetic fields, and integrate these two components to explore whether the unusual mantle beneath South Africa and Patagonia (the African Low Shear Velocity Province) places a first-order control on the character of the South Atlantic Anomaly.该项目将促进与南非，博茨瓦纳和津巴布韦的考古学家的国际合作，开发了修订的地球法守则，该法规将提供给社区，并支持研究生和本科生，这些学生将在领域接受广泛的培训，实验性的摇滚和古莫格尼派的研究将支持该纪律和地球物理学的研究。进一步完善考古记录，并更直接地测试低剪切速度省对地磁场特征的控制的效率。具体而言，研究小组将：（i）进行现场研究，包括现场调查和收集材料，目的是完善铁器时代的考古磁记录，并潜在地应用于深层地球和考古问题； （ii）进行岩石磁性，分析显微镜和古磁分析和对现场磁调查数据的处理，以定义收集位点的环境磁场，收集的考古文物中的磁载体以及对方向和强度的古老记录，以测试提议的工作的初级假设； （iii）使用数值动力模拟来调查非洲大型低剪切速度省是否可以在局部缺陷核心流动，将磁性雷诺数推向统一，有利于磁性扩散和驱逐磁性，从而将一阶控制放在地球上的地位上的授权奖学下，并通过nsf的基础进行了努力。优点和更广泛的影响审查标准。