A high-order model of the Earth's External and Induced Magnetic Field

几个世纪以来，人们一直使用磁罗盘来引导他们的方式和探索新的领域。这使得科学家们开始了他们自己的地磁发现之旅，并发现了现代技术的核心--手机、电视、电脑等--电磁学。现在，在GPS时代，你可能会认为指南针已经过时了，但地球磁场的引导对于勘探地下石油和矿物仍然至关重要具有讽刺意味的是，GPS受到地球磁场引起的自然灾害的影响。因此，对地球磁场的科学研究在许多方面仍然很重要，2012年，欧洲航天局将启动一项名为Swarm的使命，其中三颗卫星将绕地球轨道运行，以前所未有的详细程度调查地球磁场。这些测量结果将用于改进地磁场的数学模型，为各种应用提供标准参考。一个目标领域是更好地了解和描述由高层大气和空间中的电流流动造成的相对快速和复杂的磁场波动，这些波动最终是由太阳上发生的扰动驱动的，这些扰动以11年的太阳周期起起伏伏。这种所谓的外部磁场也会在海洋和地球表面下感应电流，从而产生额外的磁场波动。外部磁场和感应磁场（EIMF）一起限制了地磁场模型的准确性，因此在EIMF波动较大的地方和时间，它们对测量和导航没有用处。例如在极地地区和在可能每月发生一次并持续数天的所谓磁暴期间。EIMF还对大型导电系统造成自然危害，例如电网停电、石油管道腐蚀，甚至铁路信号幻影。在本项目中，我们将使用在世界各地300多个不同地点进行的太阳周期测量值来研究EIMF，这些测量值最近由一个名为SuperMAG的国际项目首次收集。我们的想法是借用气象学家通常用于研究天气和气候的数学技术，以确定EIMF的自然周期和模式。结合Swarm使命，由此产生的对EIMF“天气”和“气候”的新描述和理解将有助于改进下一代地球磁场的计算机模型。它也可以用来作为一个基础，以评估和预测的风险，在英国的国家电网所造成的电力中断的极端EIMF波动。

For centuries people have used magnetic compasses to guide them on their way and explore new territories. This has led scientists to embark on their own journeys of discovery about Earth's magnetism, and to the discovery of electromagnetism that is at the heart of modern technology - phones, TVs, computers, etc. Now, in the age of GPS, you might think that compasses are obsolete, but guidance by the Earth's magnetic field is still vital to explore for oil and minerals below ground (where GPS can't reach) and as a safety backup for planes etc. And ironically, GPS is affected by natural hazards caused by the Earth's magnetic field.So the scientific study of Earth's magnetism continues to be important in many ways, so much so that in 2012 the European Space Agency will launch a mission called Swarm in which three satellites will orbit the Earth to survey its magnetic field in unprecedented detail. These measurements will be used to improve mathematical models of the geomagnetic field that provide a standard reference for various applications. One target area is a better understanding and description of the relatively rapid and complex magnetic fluctuations caused by electrical currents flowing in the upper atmosphere and in Space, ultimately driven by disturbances happening on the Sun that wax and wane with an 11-year solar cycle. This so-called external magnetic field also induces currents to flow in oceans and under the Earth's surface which in turn creates additional magnetic fluctuations.Together, the external and induced magnetic field (EIMF) limits the accuracy of geomagnetic field models such that they aren't useful for surveys and navigation at places and times when the EIMF fluctuations are large, such as in the polar regions and during so-called magnetic storms that may happen once a month and last several days. The EIMF also creates a natural hazard for large-scale electrically conducting systems such as power outages in electricity grids, corrosion in oil pipelines, and even phantom railway signals.In this project we will study the EIMF using a solar cycle's worth of measurements made at over 300 different locations around the world, recently collected together for the first time by an international project called SuperMAG. Our idea is to borrow mathematical techniques usually used by meteorologists for studying the weather and climate to identify the natural cycles and patterns of the EIMF. In conjunction with the Swarm mission, the resulting new descriptions and understanding of the EIMF "weather" and "climate" should help to improve the next generation of computer models of Earth's magnetic field. It can also be used to as a basis to assess and predict the risk of power outages in UK's National Grid caused by extreme EIMF fluctuations.