Machine Learning in Space Weather
（2020 by Mandar Chandorkar ）
Summary
Machine Learning in Space Weather
Forecasting, Identification & Uncertainty Quantification
The study of variations in the space environment between the Sun and the Earth constitutes the core of space weather research. Plasma ejected by the Sun couples with the Earth's magnetic field in complex ways that determine the state of the Earth's magnetosphere. Adverse effects from space weather can impact communication networks, power grids and logistics infrastructure, all crucial pillars of a civilization that is reliant on technology.
It is important to use data sources, scientific knowledge and statistical techniques to create space weather forecasting and monitoring systems of the future. This thesis aims to be a step towards that goal. The work is organised into the following chapters.
In chapters 4 and 5, we develop probabilistic forecasting models for predicting geo-magnetic time series. Combining ground based and satellite measurements, we propose a gaussian process model for forecasting of the Dst time series one hour ahead. We augment this model with a long short-term memory (LSTM) network and produce six-hour-ahead probabilistic forecasts for Dst.
Quantifying uncertainties in the dynamics of the Earth's radiation belt is an important step for producing ensembles of high fidelity simulations of the magnetosphere. In chapter 6, we infer uncertainties in magnetospheric parameters, using data from probes orbiting in the radiation belts, by combining simplified physical models of the radiation belt with Markov Chain Monte Carlo techniques.
太阳与地球之间空间环境变化的研究构成了空间天气研究的核心。太阳喷射出的等离子体以复杂的方式与地球磁场相互作用，从而决定了地球磁层的状态。空间天气的不利影响可能波及通信网络、电网和物流基础设施，这些都是依赖技术的文明社会的重要支柱。
利用数据源、科学知识和统计技术来创建未来的空间天气预报和监测系统至关重要。本论文旨在向这一目标迈进。论文内容组织如下章节：
第二章概述了空间天气的研究历史。第三章介绍了相关空间物理背景知识。
在第四章和第五章中，我们开发了用于预测地磁时间序列的概率预测模型。通过结合地面和卫星测量数据，我们提出了一种高斯过程模型，用于提前一小时预测Dst时间序列。我们在此模型基础上增加了长短期记忆（LSTM）网络，并生成了Dst的六小时前概率预测。
量化地球辐射带动力学中的不确定性是生成高保真度磁层模拟集合的重要步骤。在第六章中，我们利用在辐射带中轨道运行的探测器数据，结合辐射带的简化物理模型和马尔可夫链蒙特卡洛技术，推断了磁层参数中的不确定性。
Historical Perspectives
Earth, Wind, Fire & Water, the classical elements were the basis for understanding our environment during antiquity. Modern science, based on experiments, has taken a very different view of the world, one based on atoms, fundamental particles, and states of matter. However, we could argue that the classical elements were a more philosophical idea that distilled our everyday experiences with nature. In fact, many ancient cultures such as Hellenistic Greece, Babylonia, Japan, Tibet, China, and India had similar lists of four or five elements. These civilizations had very different views on the properties of these elements and how they related to natural phenomena, quite often these links were mythological. The obvious way in which people experienced the classical elements was through weather systems.
From the seasons to daily weather variations, nature's elements drive and shape our lives. Sometimes weather has had a direct impact on entire populations. One example was the failed Mongol invasions of Japan in 1274 and 1281. In both attacks, the Mongol fleets were almost entirely destroyed by storms called kamikaze (translates to divine wind). Although some attacking Mongol forces did manage to land during the 1274 campaign and outnumbered the defending armies, they were still defeated by Samurai clans with superior knowledge of the terrain.
The invading fleet of 1281 was composed of 'more than four thousand ships bearing nearly 140, 000 men' [McClain, 2002, pg. 17], the scale of which was eclipsed only by the allied invasion of Normandy in 1944. The fleet was a hastily assembled, consisting of ships which were not suitable for the harsh waters between Japan and Korea. The Japanese had built two metre high walls in the intervening period and the invading fleets were forced to stay in sea for months. After their supplies were diminished, powerful kamikaze winds destroyed them entirely (an artist's view of the event is illustrated in figure 2.1). The failed invasions were a blow to the idea of Mongol supremacy in Asia and the Mongols never attempted an invasion of Japan since.
We now know that weather phenomena are caused by a combination of air pressure, temperature, and moisture differences between one place and another. The angle of the Sun's rays changes with latitude, and these variations create very different temperature trends from the poles to the equator. These differences in temperature lead to large scale air currents which create complex weather systems and climate patterns which we see across the world. But weather phenomena are hardly exclusive to planet Earth.
历史视角
地球、风、火与水，这四大古典元素是古代人们理解环境的基础。而现代科学，基于实验，则对世界有了截然不同的看法，它建立在原子、基本粒子和物质状态之上。然而，我们可以认为，古典元素是一种更为哲学的观念，它提炼了我们日常与自然界的经验。事实上，许多古代文明，如希腊化时代的希腊、巴比伦、日本、西藏、中国和印度，都有类似的四种或五种元素的列表。这些文明对这些元素的性质以及它们与自然现象之间的关系有着截然不同的看法，而这些联系往往带有神话色彩。人们体验古典元素最直观的方式就是通过天气系统。
从季节到日常天气的变化，自然界的元素驱动并塑造着我们的生活。有时，天气甚至对整个种群产生直接影响。一个例子就是1274年和1281年蒙古对日本的失败入侵。在两次进攻中，蒙古舰队几乎都被称为"神风"（即"神风"或"天罚"之意）的风暴摧毁。尽管在1274年的战役中，一些蒙古进攻部队确实成功登陆，并且人数上超过了防守军队，但他们最终还是被更熟悉地形的武士家族所击败。
1281年的入侵舰队由"四千多艘船，载着近14万人"组成[McClain, 2002, 第17页]，其规模仅次于1944年的诺曼底盟军登陆。这支舰队仓促组建，船只并不适合日本与韩国之间恶劣的海域。在此期间，日本人修建了两米高的城墙，入侵舰队被迫在海上停留数月。当他们的补给耗尽时，强大的"神风"彻底摧毁了他们（图2.1展示了这一事件的艺术家视角）。这两次失败的入侵沉重打击了蒙古在亚洲的霸权思想，蒙古人此后再也没有尝试入侵日本。
我们现在知道，天气现象是由不同地方之间的气压、温度和湿度的差异共同作用产生的。太阳光线的角度随纬度变化，这些变化从极点到赤道创造了截然不同的温度趋势。这些温度差异导致了大规模的气流，形成了我们在世界各地看到的复杂天气系统和气候模式。但天气现象并非地球独有。
The Final Frontier
Weather phenomena occurring on other planets have been observed even before the beginning of the space age. Jupiter's great red spot, a huge storm, has been continuously observed since 1830 [see Britannica].
Saturn's great white spot is a recurring storm system which was first used by Asaph Hall to determine the period of the planet's rotation [Wikisource, 2014]. In the 20th century, missions such as the Hubble space telescope, Voyager, Cassini, and others have shown storms and other weather phenomena on planetary bodies like Venus, Mars, Neptune, and Titan.
The principles behind many planetary weather phenomena are very similar. Each planet has a different atmosphere so weather phenomena in the solar system can have very different characteristics. Extra-terrestrial weather is just as complex and mind boggling as the weather we observe on Earth, and its scale is certainly much larger than we are used to.
However, planetary weather is just one side of the puzzle. Venturing into our cosmic neighbourhood, our solar system has another kind of weather system that has begun to be probed only very recently.
最后的边疆
在其他行星上发生的天气现象甚至在太空时代之前就已经被观测到。木星的大红斑，一场巨大的风暴，自1830年以来就一直在被持续观测[参见《不列颠百科全书》]。土星的大白斑是一个周期性出现的风暴系统，阿萨夫·霍尔首次利用它来确定该行星的自转周期[维基文库，2014年]。在20世纪，哈勃太空望远镜、旅行者号、卡西尼号等任务展示了金星、火星、海王星和土卫六等天体上的风暴和其他天气现象。许多行星天气现象背后的原理非常相似。每个行星的大气层都不同，因此太阳系中的天气现象可能具有截然不同的特征。外星天气与我们观察到的地球天气一样复杂且令人费解，而其规模当然比我们习惯的要大得多。然而，行星天气只是谜题的一面。当我们踏入宇宙的近邻，我们的太阳系还有另一种天气系统，它直到最近才开始被探测。
A Gust of Wind from the Heavens
During the last week of August 1859, several spots appeared on the surface of the Sun. Southern auroral displays were observed on August 29 as far north as Queensland, Australia. Just before noon on September 1, British astronomer Richard Carrington observed a 'white light flare' from a group of sun spots. He created a sketch of his observations which is seen in figure 2.3. Carrington's observations were independently verified by British publisher and astronomer Richard Hodgson; both of them sent their reports to the Monthly Notices of the Royal Astronomical Society.
September 1-2 1859 saw some remarkable events occur around the world. Auroral displays were observed all around the world, even in low latitude places such as Colombia [C´ardenas et al., 2016]. Auroras above the rocky mountains in the U.S were so bright that they woke up gold miners who began preparing breakfast thinking it was morning [Sten F. Odenwald]. In the northeastern U.S, people could read the newspaper by the aurora's light [Lovett].
The telegraph network in Europe and North America failed. Some operators experienced electric shocks [Board, 2008, pg. 13] while in some cases even telegraph equipment that was disconnected from the power supply could be used to transmit messages [Carlowicz and Lopez, 2002, pg. 58].
Based on global reports and observations taken by Scottish physicist Balfour Stewart at the Kew observatory in London, Carrington was able to connect events observed on Earth to what he saw on the Sun on the 1st of September [Clark and Clark, 2007]. His assertion was corroborated by other observers in the scientific community.
The storm of 1859, later known as the Carrington event, was in some ways the genesis of the Space Weather domain; however the actual term was coined much later in the 1950s. Although scientists had observed sunspots and their links to magnetic field variations on the Earth earlier, the Carrington event was a concrete example of how activity on the Sun could have potentially dramatic effects on the Earth.
来自天际的一阵风
1859年8月的最后一周，太阳表面出现了几个光点。8月29日，在澳大利亚昆士兰以北的南方地区观测到了极光现象。9月1日正午前不久，英国天文学家理查德·卡林顿观测到一群太阳黑子发出的"白光耀斑"。他绘制了一幅观测草图，如图2.3所示。卡林顿的观测结果得到了英国出版商兼天文学家理查德·霍奇森的独立验证；两人均将他们的报告发送给了《皇家天文学会月刊》。
1859年9月1日至2日，世界各地发生了一些引人注目的事件。全球范围内都观测到了极光现象，甚至在低纬度地区如哥伦比亚也能看到[C´ardenas等人，2016]。美国落基山脉上空的极光如此明亮，以至于唤醒了金矿工人，他们误以为天亮而开始准备早餐[Sten F. Odenwald]。在美国东北部，人们可以借着极光的光亮阅读报纸[Lovett]。
欧洲和北美的电报网络出现故障。一些电报员遭受了电击[Board，2008，第13页]，而在某些情况下，即使电报设备与电源断开连接，也能用来传递信息[Carlowicz和Lopez，2002，第58页]。
根据全球报告和苏格兰物理学家巴尔弗·斯图尔特在伦敦邱园天文台进行的观测，卡林顿能够将地球上观测到的事件与他9月1日在太阳上看到的现象联系起来[Clark和Clark，2007]。他的断言得到了科学界其他观察者的证实。
1859年的风暴，后来被称为卡林顿事件，在某种程度上是太空天气领域的起源；然而，"太空天气"这一术语直到20世纪50年代才被创造出来。尽管科学家们之前已经观察到了太阳黑子及其与地球磁场变化之间的联系，但卡林顿事件是一个具体的例子，说明了太阳上的活动可能对地球产生潜在的巨大影响。
Space Weather
How do spots and ejections from the Sun produce bright lights and currents on Earth? During Carrington's time, progress in the fledgling science of electromagnetism had picked up and enabled some understanding of the link between solar outbursts and geomagnetic phenomena. Faraday's induction experiment in 1831 (figure 2.4) demonstrated that varying magnetic fields could induce electrical currents in copper wires. It took approximately a century from the Carrington event for a theoretical understanding of Space Weather phenomena to develop. Maxwell's equations of electromagnetism [Maxwell, 1865] published in 1864 gave scientists the mathematical tools to model the motions of charged particles in electric and magnetic fields, and the variations in the fields themselves due to their motions.
Rapid progress was made in the 20th century in modelling the motions of charged particles trapped in the Earth's magnetic field, in the area of plasma physics. Plasma was the name given to the state of matter which existed as an ionised gas. From the scientific advances made in space weather and plasma physics, we know that the Carrington white light flare in 1859 was accompanied by a large release of energetic plasma from the Sun's atmosphere, also known as a coronal mass ejection (CME). The CME associated with the Carrington event was particularly energetic and compressed the Earth's magnetic field causing currents to flow in conducting materials like telegraph equipment.
Space weather started gaining relevance with the rise of space missions, and increasing reliance on communications networks. The risks posed by space weather to space faring assets like satellites meant that understanding and forecasting space weather events became especially important; although there is still much progress yet to be made.
空间天气
太阳上的斑点和喷射物如何在地球上产生明亮的光和电流？在卡林顿的时代，电磁学这门新兴科学已经取得了进展，使人们能够初步理解太阳爆发与地磁现象之间的联系。法拉第在1831年的感应实验（图2.4）表明，变化的磁场可以在铜导线中引发电流。从卡林顿事件到对太空天气现象的理论理解的发展，大约经历了一个世纪的时间。麦克斯韦在1864年发表的电磁学方程组[麦克斯韦，1865]为科学家提供了数学工具，用于模拟电场和磁场中带电粒子的运动，以及这些场本身因粒子运动而产生的变化。
20世纪，在等离子体物理学领域，对地球磁场中捕获的带电粒子运动的建模取得了迅速进展。等离子体是指电离气体的物质状态。从太空天气和等离子体物理学的科学进步中，我们了解到1859年的卡林顿白光耀斑伴随着太阳大气层中大量高能等离子体的释放，这也被称为日冕物质抛射（CME）。与卡林顿事件相关的CME特别强大，它压缩了地球的磁场，导致电流在导电材料如电报设备中流动。
随着太空任务的兴起和对通信网络依赖性的增加，太空天气开始变得重要起来。太空天气对太空航行资产（如卫星）构成的风险意味着理解和预测太空天气事件变得尤为重要；尽管在这方面仍有待取得更多进展。
Impacts
The Quebec power grid failure of 1989 [Kappenman et al., 1997] during a geomagnetic storm event showed that intense space weather events like the one observed in 1859 could cause significant damage to communications, energy, and technological infrastructure that is so crucial to the working of modern civilization.
It is now widely accepted that space weather events can adversely impact satellite and communication infrastructure, airline industry, navigation systems and the electric power grid [Board et al., 2009, Cannon et al., 2013, Bothmer and Daglis, 2007, Baker et al., 2004]. To protect our technological systems and humans in deep space exploration, it is necessary to have an advance knowledge of the changes in space weather that can pose potential threats.
影响
1989年魁北克电网故障[Kappenman等人，1997]发生在一次地磁暴事件中，这表明像1859年观测到的那种强烈太空天气事件可能对现代文明运作至关重要的通信、能源和技术基础设施造成重大损害。
现在人们普遍接受，太空天气事件会对卫星和通信基础设施、航空业、导航系统和电力网产生不利影响[Board等人，2009；Cannon等人，2013；Bothmer和Daglis，2007；Baker等人，2004]。为了保护我们的技术系统和深空探索中的人类，必须提前了解可能构成潜在威胁的太空天气变化。
The Future
The solar storms observed in the 20th and 19th centuries are only one part of the picture. It is now increasingly likely that private companies will be making significant inroads into space travel for business goals. Companies such as SpaceX and BlueOrigin aim to make space travel cheaper and more accessible so that human beings can live and work in space or other planets in the solar system, potentially starting a second space age.
This drastic move to become a multi-planetary species will bring with it risks to human life and equipment. These risks come in the form of severe magnetic storms, solar flares, and ejections of charged particles, which must be anticipated if we want to become a successful space faring race.
In order to design resilient technological systems for the new space age, we need to make progress in understanding and anticipating space weather phenomena. Physical theories about space plasmas needed to be combined with the data collected from space missions. The rapid rise of hardware, software, and data storage; the deluge of space mission data, and the advent of machine learning techniques means that we are in a unique position to take strides towards our space goals.
未来
19世纪和20世纪观测到的太阳风暴只是冰山一角。现在，私营公司越来越有可能在商业目标的驱动下，在太空旅行方面取得重大进展。SpaceX和BlueOrigin等公司旨在使太空旅行更加经济实惠和便捷，以便人类能够在太空或太阳系中的其他星球上生活和工作，从而可能开启第二个太空时代。
成为多行星物种的这一巨大转变将带来对人类生命和设备的风险。这些风险以严重的磁暴、太阳耀斑和带电粒子喷射的形式存在，如果我们想成为成功的太空航行种族，就必须预测这些风险。
为了为新的太空时代设计有弹性的技术系统，我们需要在理解和预测太空天气现象方面取得进展。关于太空等离子体的物理理论需要与从太空任务收集的数据相结合。硬件、软件和数据存储的迅速崛起；太空任务数据的泛滥，以及机器学习技术的出现，意味着我们正处于一个独特的地位，可以大步迈向我们的太空目标。
随着太空任务的兴起和对通信网络依赖性的增加，太空天气开始变得重要起来。太空天气对太空航行资产（如卫星）构成的风险意味着理解和预测太空天气事件变得尤为重要；尽管这方面仍有待取得更多进展。