NSFGEO-NERC: Deciphering the Dynamics of Geomagnetic Excursions

NSFGEO-NERC：破译地磁偏移的动力学

• 批准号: NE/Y003500/1
• 负责人: Christopher Davies
• 金额: $ 31.86万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FY003500%2F1
• 关键词: NSFGEO; NERC; Deciphering; Dynamics; Geomagnetic

The most striking variations of Earth's magnetic field are polarity excursions and reversals. These events, in which the global field strength can significantly weaken, are central to understanding the processes that generate and sustain the geomagnetic field in the liquid core and the societal impacts that could arise from reduced magnetic shielding of the surface environment. Excursions have received relatively little attention compared to reversals despite occurring more frequently and lasting long enough to cause potentially significant societal disruption. Now new observational models spanning the past 100 kyr are illuminating the evolution of excursional fields in previously inaccessible detail, and combined with advances in numerical simulation of the field generation process, this paves the way for a new approach to understand such enigmatic events. Several global spatial and temporal representations of Earth's magnetic field cover 0-100 ka or subsections thereof, and document up to 5 geomagnetic excursions with qualitative similarities as well as distinct differences. Formal definition of excursional field perturbations, duration, local asynchroneity, etc., can be made via the Paleosecular Variation Index allowing comparisons with numerical geodynamo simulations. Expanding the time interval to 0-120 ka we will produce the first high-resolution models with quantified uncertainty for the Post-Blake excursion at ~95 ka and the Hilina Pali excursion at ~20 ka. In parallel, numerical simulations will build on current NERC-funded research at Leeds that is defining the requirements for "Earth-like" field behavior. The focus of this proposal is to improve understanding of the nature and origin of geomagnetic excursions using these two synergistic interlinked components. We will(1) Use new and existing global and time-dependent observational models of several excursions during the last 120 kyrs to characterize field behavior before, during, and after excursions;(2) Analyse the excursion mechanism and predictability in new geodynamo simulations conducted with a dominant force balance that reflects expected behavior in Earth's liquid outer core;(3) Develop formal criteria for defining excursions and reconcile paleofield behavior with current and emerging views on Earth-like numerical dynamo simulations.A vital aspect of this proposal is exploiting existing synergy between the Scripps Institution of Oceanography (SIO) observational geomagnetic field modelling and paleosecular variation analysis and Leeds simulations of core dynamics. Observational models will contribute to new Earth-like standards for simulations, which will in turn be used to make high-resolution predictions of observable field variations that can be sought in the lower resolution observational data. We expect to enhance understanding of the dynamics of geomagnetic excursions, including their predictability and relation to polarity reversals.

地球磁场最显着的变化是极性偏移和反转。这些事件导致全球磁场强度显着减弱，对于理解在液核中产生和维持地磁场的过程以及地表环境磁屏蔽减弱可能产生的社会影响至关重要。尽管发生频率更高且持续时间足够长，足以造成潜在的重大社会混乱，但与逆转相比，偏离受到的关注相对较少。现在，跨越过去 100 kyr 的新观测模型正在以以前无法获得的细节阐明偏移场的演化，并结合场生成过程数值模拟的进展，这为理解此类神秘事件的新方法铺平了道路。地球磁场的几种全球空间和时间表示覆盖 0-100 ka 或其分段，并记录多达 5 次具有定性相似性和明显差异的地磁偏移。偏移场扰动、持续时间、局部异步性等的正式定义可以通过古变化指数进行，从而与数值地球发电机模拟进行比较。将时间间隔扩大到 0-120 ka，我们将为约 95 ka 的后布莱克偏移和约 20 ka 的希利纳巴利偏移生成第一个具有量化不确定性的高分辨率模型。与此同时，数值模拟将建立在 NERC 资助的利兹研究的基础上，该研究定义了“类地”场行为的要求。该提案的重点是利用这两个协同互连的组件来提高对地磁偏移的性质和起源的理解。我们将(1)使用过去120 kyrs期间多次偏移的新的和现有的全球和时间相关观测模型来描述偏移之前、期间和之后的场行为；(2)分析新的地球发电机模拟中的偏移机制和可预测性，该模拟以反映地球液体外核预期行为的主导力平衡进行；(3)制定定义偏移的正式标准，并将古田行为与当前和新兴的观点相协调 该提案的一个重要方面是利用斯克里普斯海洋学研究所（SIO）观测地磁场建模和古世变分析以及利兹核心动力学模拟之间现有的协同作用。观测模型将有助于制定新的类地模拟标准，而这些标准又将用于对可观测场变化进行高分辨率预测，这些变化可以在较低分辨率的观测数据中寻找。我们希望加强对地磁偏移动力学的理解，包括它们的可预测性以及与极性反转的关系。