Stochastic optimisation of absolute geomagnetic palaeointensity determinations

绝对地磁古强度测定的随机优化

• 批准号: NE/F015208/1
• 负责人: Andrew Biggin
• 金额: $ 57.19万
• 依托单位: University of Liverpool
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF015208%2F1
• 关键词: Stochastic; optimisation; absolute; geomagnetic; palaeointensity

I propose to develop a new mathematical tool that will make measurements of the Earth's magnetic field strength in the ancient past much more reliable and efficient. The magnetic field of the Earth extends far into space and is important to humans for many reasons. It is used by us and other species for navigation and it also protects human technology from the 'solar wind' - a stream of high-energy particles emitted by the sun. The interaction of the solar wind with the Earth's magnetic field causes aurorae (the Northern and Southern Lights) and other 'space weather' phenomena. The initiation of a strong, global 'geomagnetic' field more than three billion years ago may have been a crucial factor in allowing the first life on Earth to appear. Before then, the atmosphere might not have been able to form because of continual erosion by the solar wind. The importance of the Earth's magnetic field to human civilisation and life in general means that it is very important that we study it and learn as much about it as we can. Another good reason for this is that it can tell us a great deal about the place where it is generated: the deep interior of the Earth. At any one point on the Earth's surface, the magnetic field has both direction and intensity which both vary rather erratically in time. To study the present-day behaviour of the Earth's magnetic field, we use specialist satellites and a global network of magnetic observatories. To study the field in the distant past, we must turn to the geological record and volcanic rocks in particular. These lock-in the direction and intensity of the field at the time and place that they cool from molten lava and therefore provide a globally-distributed 'palaeomagnetic' record for almost the whole of Earth's history. The ancient direction of the Earth's magnetic field as recorded in rocks is much easier to measure than is its ancient strength (called its 'palaeointensity'). However, absolute palaeointensity records are essential for allowing us understand the geomagnetic field and its history. The problem with measuring the palaeointensity is that the rocks which are used can be affected by many complex physical factors which can bias the result. Furthermore, the precise way the measurement is carried out can also affect its reliability. A lot of recent work has gone into improving our understanding of these problems but a lack of synthesis means that palaeomagnetists still do not agree on which rocks and experimental methods produce reliable palaeointensity measurements. There is also some disagreement over which of the thousands of palaeointensity measurements which have already been published can be trusted and which should be disregarded as unreliable. These disagreements could largely be overcome if we had objective, quantitative information about the likely success of any particular palaeointensity experiment. My proposal is to provide this by developing an entirely new 'stochastic' (i.e. partially random) numerical model of palaeointensity experiments which can optimise: experimental design, analytical and procedure, and objectively determine the reliability of published data. I will rigorously constrain and test this model using new and published experimental data and ultimately, I will employ it to obtain important new information including the strength of the Earth's magnetic field more than 3 billion years ago. The benefits of this work will be considerable. It will enable future palaeointensity studies to be performed with much greater efficiency and will also allow us to get the most out of the thousands of palaeointensity determinations which are already published. Our understanding of the Earth's magnetic field, its formation in the outer core, and its protection of society and life as a whole will all be improved as a result.

我建议开发一种新的数学工具，使古代地球磁场强度的测量更加可靠和高效。地球的磁场延伸到太空深处，出于多种原因对人类很重要。它被我们和其他物种用于导航，还保护人类技术免受“太阳风”（太阳发出的高能粒子流）的影响。太阳风与地球磁场的相互作用导致极光（北极光和南极光）和其他“太空天气”现象。三十亿多年前，强大的全球“地磁”场的形成可能是地球上第一个生命出现的关键因素。在此之前，由于太阳风的持续侵蚀，大气层可能无法形成。地球磁场对人类文明和生命的重要性意味着我们研究它并尽可能多地了解它非常重要。另一个很好的理由是它可以告诉我们很多关于它产生的地方的信息：地球的深处。在地球表面的任何一点，磁场都有方向和强度，并且随时间变化相当不稳定。为了研究地球磁场的当前行为，我们使用专业卫星和全球磁观测站网络。为了研究遥远过去的领域，我们必须转向地质记录，特别是火山岩。它们锁定了从熔岩中冷却的时间和地点的磁场方向和强度，因此为几乎整个地球历史提供了全球分布的“古地磁”记录。岩石中记录的地球磁场的古代方向比其古代强度（称为“古强度”）更容易测量。然而，绝对古强度记录对于我们了解地磁场及其历史至关重要。测量古强度的问题在于，所使用的岩石可能受到许多复杂的物理因素的影响，这些因素可能会导致结果出现偏差。此外，测量的精确方式也会影响其可靠性。最近的许多工作都致力于提高我们对这些问题的理解，但缺乏综合意味着古地磁学家仍然无法就哪些岩石和实验方法产生可靠的古强度测量达成一致。对于已经发表的数千个古强度测量值中哪些是可信的、哪些应该被视为不可靠而被忽视，也存在一些分歧。如果我们有关于任何特定古强度实验可能成功的客观、定量信息，这些分歧在很大程度上可以得到克服。我的建议是通过开发一种全新的“随机”（即部分随机）古强度实验数值模型来实现这一点，该模型可以优化：实验设计、分析和程序，并客观地确定已发表数据的可靠性。我将使用新的和已发表的实验数据严格约束和测试这个模型，最终我将利用它来获取重要的新信息，包括 30 亿多年前地球磁场的强度。这项工作的好处将是巨大的。它将使未来的古强度研究能够以更高的效率进行，也将使我们能够充分利用已发表的数千个古强度测定结果。我们对地球磁场、其外核形成​​及其对整个社会和生命的保护的理解都将因此得到改善。

项目成果

Rapid regional perturbations to the recent global geomagnetic decay revealed by a new Hawaiian record.

夏威夷的一项新记录揭示了最近全球地磁衰变的快速区域扰动。

• DOI: http://dx.10.1038/ncomms3727
• 发表时间: 2013
• 期刊: Nature communications
• 影响因子: 16.6
• 作者: De Groot LV

High paleointensities for the Canary Islands constrain the Levant geomagnetic high

加那利群岛的高古强度限制了黎凡特地磁强

• DOI: 10.1016/j.epsl.2015.03.020
• 发表时间: 2015-06-01
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: L. Groot;Annemarieke Béguin;M. Kosters;E. Rijsingen;E. Struijk;A. Biggin;E. Hurst;C. Langereis;M. Dekkers
• 通讯作者: M. Dekkers

Possible links between long-term geomagnetic variations and whole-mantle convection processes

长期地磁变化与全地幔对流过程之间的可能联系

• DOI: 10.1038/ngeo1521
• 发表时间: 2012-04-01
• 期刊: Nature Geoscience
• 影响因子: 18.3
• 作者: A. Biggin;B. Steinberger;J. Aubert;N. Suttie;R. Holme;T. Torsvik;D. G. Meer;D. Hinsbergen
• 通讯作者: D. Hinsbergen

The effect of cooling rate on the intensity of thermoremanent magnetization (TRM) acquired by assemblages of pseudo-single domain, multidomain and interacting single-domain grains

冷却速率对赝单畴、多畴和相互作用单畴晶粒组合获得的热剩磁（TRM）强度的影响

• DOI: 10.1093/gji/ggt078
• 发表时间: 2013-06-01
• 期刊: Geophysical Journal International
• 影响因子: 2.8
• 作者: A. Biggin;S. Badejo;E. Hodgson;A. Muxworthy;J. Shaw;M. Dekkers
• 通讯作者: M. Dekkers

Archaeomagnetic study of five mounds from Upper Mesopotamia between 2500 and 700 BCE: Further evidence for an extremely strong geomagnetic field ca. 3000 years ago

对公元前 2500 年至 700 年美索不达米亚上游五个土丘的考古磁学研究：关于极强地磁场的进一步证据

• DOI: 10.1016/j.epsl.2012.08.039
• 发表时间: 2012-12-01
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: P. Ertepinar;C. Langereis;A. Biggin;M. Frangipane;T. Matney;T. Ökse;A. Engin
• 通讯作者: A. Engin