Visiting Researchers in Space Environment Physics

我们研究的对象是北极光，这是天空中令人惊叹的自然灯光秀。我们使用极光作为诊断手段，以了解地球周围空间环境的许多情况。这个环境是由“等离子体”(电离气体)组成的，它占宇宙中直接可见物质的95%以上，但奇怪的是，在地球生物圈内维护和研究是非常困难的。极光似乎是无处不在的磁化行星的属性，它从太阳系以外的行星上探测到它将给我们一个独特的详细信息，了解它们的磁场和大气。极光的故事始于太阳，太阳是一种连续但非常可变的能源，以等离子流(太阳风)的形式影响地球。极光现象经常出现在高纬度地区，比如北斯堪的纳维亚半岛，只有在英国的纬度地区才会出现极光。为了研究极光，我们使用了一种特殊的仪器，它有三个摄像头同时拍摄不同的颜色。拟议的研究是为了在尽可能高的分辨率下研究非常动态和有结构的极光。该仪器被命名为Ask for Aural Structure and Kinetics。它的设计是测量磁天顶上一个3度的小圆圈，即沿着地球磁场垂直向上。来自太阳的粒子沿着这些假想的磁力线螺旋上升，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)取决于入射粒子开始时的能量大小，以及它击中的分子或原子。ASK相机通过在空间和时间上非常精确地测量三种不同物理来源的排放物，帮助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结果来提供有关极光的更多信息。我们在斯瓦尔巴特群岛进行研究，斯瓦尔巴特群岛位于遥远的北方，冬季的几个月里整天都是黑暗的，这是进行光学测量的理想地点。当粒子被困在地球磁场中时，它们是如何获得如此多的能量的，目前还不完全清楚。自太空时代以来，火箭和卫星通过极光事件飞行，回答了许多关于极光的问题。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。有许多极光粒子加速理论在解释极光行为方面取得了不同程度的成功；然而，到目前为止，还没有一个理论可信地解释极光弧会如此细小和动态。高层大气中的等离子体是距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的许多现象已经应用于聚变研究、太阳物理和天体物理。我们的目标是继续这一进程。近年来，已经很明显的是，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。这被称为AKR(极光基波辐射)。由于极光和AKR是由太阳系中所有磁化的行星产生的，我们设想有一天，空间无线电探测器(可能在月球上)和特别大的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找到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.