Stochastic optimisation of absolute geomagnetic palaeointensity determinations

我建议开发一种新的数学工具，使测量古代地球磁场强度更加可靠和有效。地球的磁场延伸到遥远的太空，对人类很重要，原因有很多。它被我们和其他物种用于导航，它也保护人类技术免受“太阳风”——太阳发射的高能粒子流的影响。太阳风与地球磁场的相互作用导致了极光（北极光和南极光）和其他“太空天气”现象。30多亿年前，一个强大的全球“地磁场”的形成可能是地球上第一批生命出现的关键因素。在那之前，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是非常重要的。另一个很好的原因是，它可以告诉我们很多关于它产生的地方：地球的深处。在地球表面的任何一点，磁场都有方向和强度，它们都随时间变化得相当不规律。为了研究当今地球磁场的行为，我们使用了专门的卫星和全球磁观测站网络。要研究遥远的过去，我们必须求助于地质记录，特别是火山岩。这些锁定了它们从熔岩中冷却下来的时间和地点的磁场方向和强度，因此提供了几乎整个地球历史的全球分布的“古地磁”记录。岩石中记录的地球磁场的古代方向比测量其古代强度（称为“古强度”）要容易得多。然而，绝对的古强度记录对于我们了解地磁场及其历史是必不可少的。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，这些因素可能会使结果产生偏差。此外，精确的测量方式也会影响其可靠性。最近的许多工作都是为了提高我们对这些问题的理解，但由于缺乏综合，古地磁学家在哪些岩石和实验方法能产生可靠的古强度测量上仍然没有达成一致。在已经发表的数以千计的古强度测量中，哪些是可信的，哪些是不可靠的，也存在一些分歧。如果我们有关于任何特定的古强度实验可能成功的客观、定量的信息，这些分歧就可以在很大程度上被克服。我的建议是通过开发一种全新的“随机”（即部分随机）古强度实验的数值模型来提供这一点，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。我将严格约束和测试这个模型，使用新的和已发表的实验数据，最终，我将利用它来获得重要的新信息，包括30多亿年前地球磁场的强度。这项工作的好处将是可观的。它将使未来的古强度研究更有效率，也将使我们从已经发表的数千个古强度测定中得到最大的收获。因此，我们对地球磁场、它在地核外的形成以及它对整个社会和生命的保护的理解都将得到改善。

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.