Balancing the magnetosphere's magnetic flux budget

平衡磁层的磁通量预算

• 批准号: ST/K004298/1
• 负责人: Robert Fear
• 金额: $ 56.04万
• 依托单位: University of Leicester
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FK004298%2F1
• 关键词: Balancing; magnetosphere; magnetic; flux; budget

Many bodies in the universe have their own magnetic fields. The Sun's magnetic field extends out to the furthest reaches of the Solar System, and the magnetic field of a magnetised planet carves out a region of space called the planet's "magnetosphere". It is the interplay between the magnetic fields of the Sun and the Earth's magnetosphere that transfers huge amounts of energy and drives most of the activity within the magnetosphere. In this study, I will gain a more comprehensive understanding of the fundamental processes driving this response. However, a wider application of the science in this field is the ever-improving forecasts of space weather (the conditions in near-Earth space). This is of real importance in the modern age, with our reliance on satellites and other technologies that are sensitive to solar activity.We know broadly how the region of space near Earth responds to solar activity. The Sun continuously spews out a hot gas (a plasma) called the solar wind, which flows through the Solar System. As it does so, it carries the Sun's magnetic field with it. The Earth's magnetic field protects us from the solar wind by forming a cavity called the magnetosphere. As the solar wind buffets the magnetosphere, the Sun's and Earth's magnetic fields collide. Sometimes, the two magnetic fields interlock and become connected in a process called 'reconnection'. This transfers energy from the Sun to the magnetosphere. This energy drives a lot of dynamic processes in the magnetosphere, such as increases in the intensity of the Van Allen radiation belts and geomagnetic storms, which can damage satellites and infrastructure on the ground. When the energy is released energetic particles are deposited into the atmosphere. This gives off light in an oval-shaped band around the North Pole and another around the South Pole which is called the 'aurora' or the northern and southern lights. (In the north, the oval usually stretches through Scandinavia, Siberia, Alaska and Canada, which is why these are the best places to see the northern lights.)Many parts of this chain of events are poorly understood, and I will make advances in two key areas. Firstly, we do not understand exactly how the 'interlocking' process happens. We cannot even agree how much interlocking takes place; people have tried to measure this by using satellites and radars that see the effects in the ionosphere (a layer of the upper atmosphere), and get wildly different answers. By taking a new approach developed from some of my recent work, I will be able to measure this effect accurately; I am confident that my estimates from spacecraft and ionospheric measurements will agree.The second aspect I will study is how the magnetosphere behaves when the Earth's and Sun's magnetic fields do not interlock. We know that under these conditions auroras form in a different way - rather than just forming in an oval around the pole, they are also seen at higher latitudes. We do not fully comprehend how high latitude auroras are formed, or how the magnetosphere behaves under these conditions. By making measurements of both the aurora and the environment in the magnetosphere, I will be able to work this out.These two questions are different sides to the problem of understanding how our environment is driven by the solar wind. Gaining a thorough understanding of this is important for two reasons. First, space weather forecasting requires a detailed knowledge of how the magnetosphere works and how it responds to the solar wind. Second, the 'interlocking' process (reconnection) occurs throughout the universe, and so understanding it is vital if we are to comprehend the workings of a large number of astronomical objects. The quality and range of measurements that can be made in the magnetosphere make it the best place to observe and understand reconnection.

宇宙中的许多天体都有自己的磁场。太阳的磁场延伸到太阳系的最深处，而被磁化的行星的磁场在太空中划出一个区域，称为行星的“磁层”。正是太阳磁场和地球磁层之间的相互作用，转移了大量的能量，并驱动了磁层内的大部分活动。在这项研究中，我将对驱动这种反应的基本过程有更全面的了解。然而，科学在这一领域的一个更广泛的应用是不断改进的空间天气预报（近地空间的条件）。这在现代是非常重要的，因为我们依赖于卫星和其他对太阳活动敏感的技术。我们大致知道地球附近的空间区域对太阳活动的反应。太阳不断地喷出一种叫做太阳风的热气体（一种等离子体），这种气体流经太阳系。当它这样做的时候，它携带着太阳的磁场。地球磁场通过形成一个叫做磁层的空腔来保护我们免受太阳风的侵害。当太阳风冲击磁层时，太阳和地球的磁场发生碰撞。有时，两个磁场互锁并在称为“重连”的过程中连接起来。这将能量从太阳转移到磁层。这种能量驱动了磁层中的许多动态过程，例如范艾伦辐射带和地磁风暴强度的增加，这可能会破坏卫星和地面上的基础设施。当能量释放时，高能粒子沉积到大气中。它在北极周围发出椭圆形的光，在南极周围发出另一个椭圆形的光，这被称为极光或北极光和南极光。（在北部，椭圆形通常延伸到斯堪的纳维亚半岛、西伯利亚、阿拉斯加和加拿大，这就是为什么这些地方是观赏北极光的最佳地点。）人们对这一系列事件的许多部分知之甚少，我将在两个关键领域取得进展。首先，我们并不确切地了解“连锁”过程是如何发生的。我们甚至无法就连锁作用的程度达成一致；人们试图通过卫星和雷达来测量电离层（上层大气的一层）的影响，并得到了截然不同的答案。通过采用一种从我最近的工作中发展出来的新方法，我将能够准确地测量这种效应；我有信心，我从航天器和电离层测量中得出的估计将与之一致。我要研究的第二个方面是，当地球和太阳的磁场不联锁时，磁层是如何表现的。我们知道，在这些条件下，极光以不同的方式形成——不仅仅是在极点周围形成椭圆形，在高纬度地区也能看到极光。我们并不完全了解高纬度极光是如何形成的，或者磁层在这些条件下是如何表现的。通过对极光和磁层环境的测量，我就能算出来。这两个问题是理解我们的环境是如何被太阳风驱动的问题的不同方面。彻底理解这一点很重要，原因有二。首先，太空天气预报需要详细了解磁层如何工作以及它对太阳风的反应。其次，“连锁”过程（重新连接）发生在整个宇宙中，因此，如果我们要理解大量天文物体的工作原理，了解它是至关重要的。在磁层中可以进行的测量的质量和范围使其成为观察和理解重联的最佳地点。

项目成果

Saturn's elusive nightside polar arc

• DOI: 10.1002/2014gl061081
• 发表时间: 2014-09
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: A. Radioti;D. Grodent;J. Gérard;S. Milan;R. Fear;C. Jackman;B. Bonfond;W. Pryor

Solar illumination control of ionospheric outflow above polar cap arcs

极冠弧上方电离层流出的太阳光照控制

• DOI: 10.1002/2014gl062972
• 发表时间: 2015
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Maes L

The interaction between transpolar arcs and cusp spots

• DOI: 10.1002/2015gl066194
• 发表时间: 2015-11
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: R. Fear;S. Milan;J. Carter;R. Maggiolo

A statistical study of magnetospheric ion composition along the geomagnetic field using the Cluster spacecraft for L values between 5.9 and 9.5

使用 Cluster 航天器对 L 值在 5.9 至 9.5 之间的磁层离子组成进行统计研究

• DOI: 10.1002/2015ja022261
• 发表时间: 2016
• 期刊: Space Physics
• 作者: Sandhu J

Transpolar arc observation after solar wind entry into the high-latitude magnetosphere

太阳风进入高纬磁层后的跨极弧观测

• DOI: 10.1002/2014ja020912
• 发表时间: 2015
• 期刊: Journal of Geophysical Research-Space Physics
• 影响因子: 2.8
• 作者: Mailyan B.;Shi Q. Q.;Kullen A.;Maggiolo R.;Zhang Y.;Fear R. C.;Zong Q. -G.;Fu S. Y.;Gou X. C.;Cao X.;Yao Z. H.;Sun W. J.;Wei Y.;Pu Z. Y.
• 通讯作者: Pu Z. Y.