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A New Generation of Forward and Inverse Geodynamo Models

新一代正向和逆向地球发电机模型

基本信息

批准号：
NE/G014043/1
负责人：
Philip William Livermore
金额：
$ 61.6万
依托单位：
University of Leeds
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%2FG014043%2F1
关键词：
New Generation Forward Inverse Geodynamo

项目摘要

Have you ever wondered why compasses point north? This fundamental question, still unsolved, has perplexed many scientists including the likes of Einstein. Scientists now accept that the source of the geomagnetic field lies inside Earth's core and, like a giant bar magnet thousands of miles beneath our feet, radiates tentacle-like magnetic field lines that penetrate the mantle and wrap around the Earth. Although it is apparent that, at the Earth's surface, the geomagnetic field is principally dipolar (having north and south poles), images of the field at the edge of the core show many more complex features. Furthermore, the geomagnetic field varies slowly with time. Although over the duration of a human lifetime these changes are small, geologists have shown that, over the course of the Earth's history, the geomagnetic field globally reverses: the north and south poles swap places a few times every million years or so. The geomagnetic field is not only crucial for navigation (by many animals, as well as humans) but provides us with an electromagnetic shield that protects our planet from harmful solar and interstellar radiation, and consequently has a potentially important influence on climate. Of particular interest is the recent evidence that the Earth's dipolar field is losing strength and that it may completely reverse within 2000 years. During reversals the electromagnetic shield is significantly weakened and, although our ancestors have survived many such events apparently without harm, it is unknown how the many satellites and other technological infrastructure, that our society relies upon, will be affected. A full understanding of the generation of the Earth's magnetic field and its reversals would undoubtedly help us to limit any destructive effects that might occur. The geomagnetic field is generated by the so-called geodynamo mechanism, powered by motions of molten iron in the Earth's core. Scientists study the geodynamo by using complex computer models that simulate the processes in the core. However, because of severe computational difficulties inherent in current techniques, the physical properties of the modelled Earth must be altered in order to make the problem solvable on present-day computers. It is not possible to faithfully simulate the Earth's core, and opinion remains divided over the many interpretations of such geodynamo models, including the trigger for global reversals. An additional technique is to use observations of the magnetic field on Earth's surface to image the field and the structure of the flow of molten iron at the edge of the core. This has been enormously successful in revealing many interesting dynamics although, rather like attempting to understand the internal currents of the world's oceans by simply inspecting the ocean surface, it is impossible to say very much about the processes inside the core. Consequently, many aspects of the Earth's interior and source of the geomagnetic field remain a mystery. Earlier this year in an exciting new development, I presented some crucial theoretical advances that pave the way for constructing a new generation of geodynamo models. The new technique supplies a fundamentally new approach that allows realistic properties of the core to be accessed directly on computers, and I will be able to produce the first geodynamo models able to simulate the Earth's core accurately. This will enable robust characterisation of the mechanism that generates the geomagnetic field and detailed analysis of the associated phenomena, including magnetic reversals. Additionally, by further exploitation of the new theoretical developments, I will be able to use observations to probe the present-day magnetic field structure inside the core, again something that has never before been possible. These two complementary projects will revolutionise the state-of-the-art in geodynamo modelling and will provide unprecedented insights into the dynamics of the Earth's core.

你有没有想过为什么指南针指向北方？这个尚未解决的根本问题困扰着许多科学家，包括爱因斯坦这样的科学家。科学家们现在承认，地磁场的来源位于地球核心内部，就像我们脚下数千英里处的巨型条形磁铁一样，辐射出触手状的磁力线，穿透地幔并环绕地球。虽然很明显，在地球表面，地球磁场主要是偶极的(有北极和南极)，但地核边缘的磁场图像显示出更复杂的特征。此外，地磁场随时间变化缓慢。尽管在人类一生中，这些变化很小，但地质学家已经表明，在地球历史进程中，地球磁场在全球范围内发生逆转：北极和南极每百万年左右交换几次位置。地球磁场不仅对(许多动物和人类)导航至关重要，而且为我们提供了一个电磁屏，保护我们的星球免受有害的太阳和星际辐射的影响，因此对气候有潜在的重要影响。特别令人感兴趣的是，最近有证据表明，地球的偶极场正在失去强度，并可能在2000年内完全逆转。在反转期间，电磁屏蔽显著减弱，尽管我们的祖先在许多这样的事件中显然没有受到伤害，但我们的社会所依赖的许多卫星和其他技术基础设施将受到怎样的影响尚不清楚。充分了解地球磁场的产生及其逆转，无疑将有助于我们限制可能发生的任何破坏性影响。地球磁场是由所谓的地球发电机机制产生的，地球发电机机制是由地核中的熔铁运动提供动力的。科学家们通过使用复杂的计算机模型来模拟地核的过程来研究地球发电机。然而，由于当前技术固有的严重计算困难，必须改变模拟地球的物理性质，以便使问题在当今的计算机上可解。要忠实地模拟地核是不可能的，对于这样的地球发电机模型的许多解释，包括引发全球逆转的原因，意见仍然存在分歧。另一种技术是利用对地球表面磁场的观测，对地核边缘的铁水流动的磁场和结构进行成像。这在揭示许多有趣的动力学方面取得了巨大的成功，尽管就像试图通过简单地检查海洋表面来了解世界海洋的内部流动一样，不可能对核心内部的过程说得太多。因此，地球内部的许多方面和地磁场的来源仍然是一个谜。今年早些时候，在一项令人兴奋的新发展中，我提出了一些关键的理论进展，为构建新一代地球发电机模型铺平了道路。这项新技术提供了一种全新的方法，允许在计算机上直接获取地核的真实属性，我将能够制作出第一个能够准确模拟地核的地球发电机模型。这将使我们能够对产生地磁场的机制进行强有力的描述，并对相关现象进行详细分析，包括磁反转。此外，通过进一步利用新的理论发展，我将能够利用观测来探测当今地核内部的磁场结构，这也是以前从未可能做到的事情。这两个相辅相成的项目将彻底改变地球发电机建模的最先进水平，并将提供前所未有的对地核动态的洞察。