Auroral Structure and Kinetics

我们研究的主题是北极光，或称北方光，这是天空中令人惊叹的自然光秀。我们使用极光作为诊断来了解地球周围空间环境的许多事情。这种环境由“等离子体”（电离气体）组成，占宇宙中直接可观察物质的95%以上，但奇怪的是，在地球生物圈内难以维持和研究。极光似乎是磁化行星的一种普遍属性，从太阳系以外的行星上探测到极光，将使我们能够对它们的磁场和大气层有一个独特的详细了解。极光的故事始于太阳，太阳是一个连续但非常可变的能量源，以等离子流（“太阳风”）的形式影响地球。极光经常出现在高纬度地区，如斯堪的纳维亚半岛的北方，而在英国的纬度地区则很少见。为了研究极光，我们使用了一种特殊的仪器，它有三个相机同时观察不同的“颜色”。拟议的研究是为了以尽可能高的分辨率研究非常动态和结构化的极光。这台仪器被命名为ASK for Auroral Structure and Kinetics。它被设计用来测量“磁天顶”的3度小圆圈，即沿着地球磁场的直线。来自太阳的粒子沿着这些假想的磁场线螺旋运动，当它们与大气中的氧气和氮气碰撞时会失去能量。光的确切颜色（或波长）取决于入射粒子的初始能量，以及它撞击的分子或原子。ASK相机通过在空间和时间上对三种不同物理来源的辐射进行非常精确的测量，有助于解开这一复杂的过程。我们还使用雷达和其他光学仪器的测量来提供更多关于极光的信息。我们在斯瓦尔巴特群岛进行研究，斯瓦尔巴特群岛位于北方，在冬季的几个月里全天都是黑暗的，非常适合光学测量。目前还不完全清楚这些粒子是如何在被地球磁场捕获时获得如此多的能量的。自从太空时代以来，许多关于极光的问题已经从火箭和卫星穿越极光事件中得到了解答。然而，核心问题仍然存在：粒子如何在地球磁场中加速，以及它们如何在大气中形成如此复杂和动态的模式。关于极光粒子加速的理论有很多，它们在解释极光行为方面都取得了不同程度的成功;然而，迄今为止，还没有一个理论能够合理地解释极光弧为什么会如此薄和动态。高层大气中的等离子体是离我们最近的大规模等离子体，因此使用雷达和光学仪器使我们能够利用这个天然的等离子体实验室。通过研究地球周围的等离子体发现了许多现象，这些现象已应用于聚变研究，太阳物理学和天体物理学。我们的目标是继续这一进程。近年来，人们已经清楚地认识到，如果一个人在太空中失踪，他或她能探测到的第一个地球信号将是由产生极光的相同加速粒子产生的无线电发射。AKR（Auroral Kilometric Radiation）。由于极光和AKR是由我们太阳系中所有被磁化的行星产生的，我们设想有一天，天基无线电探测器（可能在月球上）和超大型多段望远镜将被用来探测和分析其他恒星周围的行星。我们研究的一个长期目标是开发实现这一目标的方法。

The subject of our study is the aurora borealis, or northern lights, which is an amazing natural lightshow in the sky. We use the aurora as a diagnostic to find out many things about the space environment around the Earth. That environment is made up of 'plasma' (ionised gas) which makes up over 95% of the directly observable material in the cosmos, yet is strangely difficult to maintain and study within Earth's biosphere. Aurora appears to be a ubiquitous property of magnetised planets and its detection from planets beyond our solar system would give us a uniquely detailed view of their magnetic field and atmosphere. The story of the aurora begins at the Sun, which is a continuous but very variable energy source, in the form of a plasma stream (the 'solar wind') which impacts on the Earth. Auroral displays are regularly seen at high latitudes, such as northern Scandinavia, and only rarely at the latitudes of the UK. To study the aurora, we use a special instrument which has three cameras looking at different 'colours' simultaneously. The proposed research is for studies of very dynamic and structured aurora at the highest possible resolution. The instrument is named ASK for Auroral Structure and Kinetics. It is designed to measure a small circle of 3 degrees in the 'magnetic zenith' i.e. straight up along the Earth's magnetic field. Particles from the Sun spiral along these imaginary magnetic field lines, and lose energy when they collide with atmospheric oxygen and nitrogen. The exact colour (or wavelength of the light) depends on how much energy the incoming particle started with, and on what molecule or atom it hits. The ASK cameras help to unravel this complicated process by making very precise measurements in space and time of three emissions which have different physical origins. We also use measurements from radars and other optical instruments to give more information about the aurora. We do our research in Svalbard, which is so far north that it is dark all day in the winter months, ideal for optical measurements. It is not fully understood how the particles obtain so much energy when they are caught up in Earth's magnetic field. Many questions about the aurora have been answered since the space age from rockets and satellites flying through auroral events. However, the central question remains: how particles are accelerated inside the Earth's magnetic field, and how they make such complex and dynamic patterns in the atmosphere. There are a great many theories of auroral particle acceleration that have varying degrees of success in explaining auroral behaviour; however, none to date has credibly explained how auroral arcs can be so thin and dynamic. The plasma in the upper atmosphere is the closest large-scale plasma to us and hence using radars and optical instruments allows us to exploit this natural plasma laboratory. There are many examples of phenomena that were discovered by studying the plasma around the Earth that have been applied in fusion research, solar physics and astrophysics. We aim to continue this process. In recent years it has become clear that if a person was lost in space, the first signal of Earth he or she could detect would be a radio emission generated by the same accelerated particles that produce the aurora. This is called AKR (Auroral Kilometric Radiation). Because aurora and AKR is produced by all the magnetised planets in our solar system we envisage a time when space-based radio detectors (possibly on the Moon) and exceptionally large, multi-segment telescopes will be used to detect and analyse planets around other stars. A long-term goal of our research is to develop ways that this could be achieved.