VIRGIL: The VIRtual paleomaGnetIc Laboratory

VIRGIL：虚拟古瘤基因实验室

• 批准号: NE/V014722/1
• 负责人: Lesleis Nagy
• 金额: $ 75.34万
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV014722%2F1
• 关键词: VIRGIL; VIRtual; paleomaGnetIc; Laboratory

Earth's magnetic field has been part of our planet from early on its formation, but the processes by which it occurs are still not well understood. The first theory of magnetism by William Gilbert proposed one of the first theories of geomagnetism in his treatise "De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure (On the Magnet and Magnetic Bodies, and on That Great Magnet the Earth)" in 1600. By observing lodestone (naturally occurring magnetite deposits), Gilbert proposed that the Earth was a giant dipolar magnet, but the theory didn't account for the many small-scale variations in Earth's field over the globe such as the south Atlantic magnetic anomaly. Modern theories of geomagnetism propose that the field is formed by a vast ocean of liquid iron swirling around a solid iron core - and evidence of this exists in modern day observations the fine structure of the field. But what about the field in the past? Fortunately, rocks containing small specs of magnetic materials can record and retain Earth's ancient field over millennia, in the same way that magnetic tape can be used to record information. Unfortunately, like magnetic tape left in the sun too long, natural rocks are subject to many external factors that distort the ancient signal that they record. It is the task of palaeo- and rock magnetism to devise experiments to "clean" the signal and recover the ancient field. But how do we know that the field that we recover is the true ancient recording? This is done by understanding precisely how each small grain behaves in response to heating, changing external field and other processes (such as chemical alteration).Knowledge of Earth's field tells not just the story of the physical processes of how our planet was formed - it is also the story of human culture. It constrains dates of archaeological sites and gives us an understanding of how those sites were used, be it for cooking or the forging of metals. It tells us of natural disasters such as wildfires and the displacement human populations. The ancient field has always been with us and or planet, but the physical theories that underpin experiments to recover this vital information is flawed.The current theory of magnetic recording in natural materials was devised by Néel and Stoner & Wohlfarth and is now 70 years old. It accounts for only a tiny fraction of the grain sizes and geometries of magnetic minerals found in rocks; but the experimental protocols and analytical tools to recover the palaeomagnetic signal are still being built on this model. In this proposal I will overhaul magnetic recording theory by using micromagnetic modelling, big-data and machine learning methods to build a complete simulation of the recording process in rocks from the ground up. This will enable me to revisit the palaeomagnetic record and answer the question: "is this a good recorder"? Such an evaluation of the existing palaeomagnetic record is critical since it constrains geodynamo models and allows us to peer into the deep past of our planet. Not only that, but it will also help underpin the models that will allow us to investigate the future of the geodynamo.

地球磁场从形成之初就是我们星球的一部分，但其发生的过程仍然没有得到很好的理解。威廉·吉尔伯特在他的论文“De Magnete”中提出了最早的地磁理论之一。 , Magneticisque Corporibus, et de Magno Magnete Tellure（论磁铁和磁体，以及论地球的大磁铁）”，1600 年。通过观察磁石（天然存在的磁铁矿）沉积物），吉尔伯特提出地球是一个巨大的偶极磁体，但该理论没有解释全球范围内地球磁场的许多小规模变化，例如南大西洋磁异常，现代地磁理论提出了磁场。磁场是由围绕固体铁芯旋转的巨大液态铁海洋形成的，这一点的证据存在于现代磁场的精细结构中，但幸运的是，过去的磁场中含有小规格的磁性材料。可以记录并保留地球的就像磁带可以用来记录信息一样，不幸的是，就像磁带在阳光下放置太久一样，天然岩石也会受到许多外部因素的影响，从而扭曲了它们所记录的古代信号。古磁学和岩石磁学的任务是设计实验来“清理”信号并恢复古代磁场，但是我们如何知道我们恢复的磁场是真正的古代记录呢？响应加热、变化的外部场和其他过程（例如化学变化）。有关地球场的知识不仅讲述了我们的星球如何形成的物理过程的故事，而且还讲述了人类文化的故事，它限制了考古遗址的日期，并使我们能够了解。这些遗址是如何被使用的，无论是用于烹饪还是锻造金属，它告诉我们野火和流离失所等自然灾害一直伴随着我们和/或地球，但支撑实验的物理理论。恢复这一重要信息目前的天然材料磁记录理论是由 Néel 和 Stoner & Wohlfarth 提出的，至今已有 70 年的历史。恢复古磁信号的协议和分析工具仍在该模型的基础上构建，在本提案中，我将通过使用微磁建模、大数据和机器学习方法来彻底修改磁记录理论，以建立完整的模拟。这将使我能够重新审视古地磁记录并回答这个问题：“这是一个好的记录器”吗？对现有古地磁记录的这种评估至关重要，因为它限制了地球发电机模型并允许我们不仅如此，它还将有助于支撑我们研究地球发电机的未来的模型。

项目成果

Chasing Tails: Insights From Micromagnetic Modeling for Thermomagnetic Recording in Non-Uniform Magnetic Structures

追尾：非均匀磁结构中热磁记录的微磁建模的见解

• DOI: http://dx.10.1029/2022gl101032
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Nagy L

Magnetic Recording Stability of Taenite-Containing Meteorites

含镍纹石陨石的磁记录稳定性

• DOI: http://dx.10.1029/2022gl102602
• 发表时间: 2023
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Devienne J

Magnetic Domain States and Critical Sizes in the Titanomagnetite Series

钛磁铁矿系列的磁畴状态和临界尺寸

• DOI: http://dx.10.22541/essoar.170688764.46924474/v1
• 发表时间: 2024
• 作者: Cych B

Thermomagnetic recording stability of taenite-containing meteoritic cloudy zones

含镍纹石陨石云带的热磁记录稳定性

• DOI: http://dx.10.22541/essoar.167525233.31180340/v1
• 发表时间: 2023
• 作者: Devienne J

Micromagnetic determination of the FORC response of paleomagnetically significant magnetite assemblages

具有古地磁意义的磁铁矿组合的 FORC 响应的微磁测定

• DOI: http://dx.10.22541/essoar.170533987.78411398/v1
• 发表时间: 2024
• 作者: Nagy L