Interhemispheric high-frequency geomagnetic field dynamics

半球间高频地磁场动力学

• 批准号: RGPIN-2017-05294
• 负责人: StOnge, Guillaume
• 金额: $ 3.42万
• 依托单位: Université du Québec à Rimouski
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=765292
• 关键词: Interhemispheric; frequency; geomagnetic; field; dynamics

Recent direct observations have demonstrated that the geomagnetic field has undergone dramatic changes over the last century. This is best illustrated by changes in the position of the North Magnetic Pole (NMP) and the rapid decline of the dipole field (i.e, the main component of Earth's magnetic field). The NMP, restricted to the Canadian Arctic during historical times (last 400 yrs), has recently moved into the Arctic Ocean. Direct observations reveal that the migration of the NMP has increased dramatically since the early 1970's from 9 km/yr to 41 km/yr and to almost 60 km/yr in 2003, whereas the annual rate of change in intensity measured at the Resolute Bay geomagnetic observatory has increased from about 10 nT/yr to almost 70 nT/yr over the last 50 years. In addition, the recent migration of the NMP occurs between two important areas of observed geomagnetic fluxes in North America and Siberia. The role of these geomagnetic flux lobes in driving Holocene geomagnetic variability is currently unknown, but maybe key. Similarly, recent satellite observations in the Southern Hemisphere and geomagnetic models reveal an important magnetic anomaly developed over the last centuries in the Southern Hemisphere. The origin and cause of this anomaly, named the South Atlantic Magnetic Anomaly are still unknown. These recent spectacular changes lead to the formulation of the following questions: “Are we in the initial stages of a large-scale geomagnetic change, or even a reversal?” and “are these changes associated with the dynamics of flux lobes?”. To answer these fundamental questions, the historical record must first be placed into a longer geological context. The long-term goal of my Discovery Grant program is to determine the high frequency dynamics of the geomagnetic field during the Late Quaternary with a special emphasis on abrupt changes in the high latitudes of both hemispheres. This research program will provide the first large-scale Holocene interhemispheric study of high latitude geomagnetic field dynamics. In addition, by selecting coring sites with very high sediment accumulation rates, the proposed research will investigate geomagnetic field variability at a temporal resolution that is just beginning to be explored, the centennial to millennial timescales. These observations will: 1) enable testing of hypotheses developed from the historical geomagnetic record, 2) yield invaluable data for geodynamo modelling, and 3) place the current dramatic collapse and migration of the NMP into a detailed geological context. The proposed research will also provide novel data to enhance our understanding of Sun/Earth interactions, as the combination of paleomagnetic and 10Be analysis from the same cores will help decipher the influence of the geomagnetic field on the production rate of cosmogenic isotopes, with practical implications for dating, space weather, telecommunications and climate.

最近的直接观测表明，地磁场在上个世纪发生了巨大的变化。北磁极（NMP）位置的变化和偶极子场（即地球磁场的主要组成部分）的快速下降最能说明这一点。 NMP 在历史时期（过去 400 年）仅限于加拿大北极地区，最近已进入北冰洋。直接观测表明，自 1970 年代初期以来，NMP 的迁移急剧增加，从每年 9 公里增加到每年 41 公里，并在 2003 年增加到每年近 60 公里，而在过去 50 年里，坚毅湾地磁观测站测量的强度年变化率从约 10 nT/年增加到近 70 nT/年。此外，NMP最近的迁移发生在北美和西伯利亚两个重要的地磁通量观测区域之间。这些地磁通量瓣在驱动全新世地磁变化中的作用目前尚不清楚，但可能是关键。同样，最近对南半球的卫星观测和地磁模型揭示了南半球过去几个世纪中出现的重要磁异常。这种被称为南大西洋磁异常的异常现象的起源和原因仍然未知。最近这些引人注目的变化引发了以下问题：“我们是否正处于大规模地磁变化甚至逆转的初始阶段？”以及“这些变化是否与通量瓣的动态相关？”。为了回答这些基本问题，必须首先将历史记录置于更长期的地质背景中。我的发现资助计划的长期目标是确定第四纪晚期地磁场的高频动态，特别强调两个半球高纬度的突变。该研究计划将提供首次大规模全新世半球间高纬度地磁场动力学研究。此外，通过选择沉积物积累率非常高的取芯地点，拟议的研究将以刚刚开始探索的时间分辨率（百年到千年的时间尺度）研究地磁场变化。这些观测结果将：1）能够测试根据历史地磁记录提出的假设，2）为地球发电机建模提供宝贵的数据，3）将当前 NMP 的剧烈塌陷和迁移置于详细的地质背景中。拟议的研究还将提供新的数据，以增强我们对太阳/地球相互作用的理解，因为来自同一核心的古地磁和 10Be 分析的结合将有助于破译地磁场对宇宙同位素产生率的影响，对年代测定、空间天气、电信和气候具有实际意义。