Fine-scale auroral structure: Causes and effects

美丽的地球极光是太阳风、地球磁场和大气层相互作用的结果。带电粒子通过漏斗进入大气层，在那里它们撞击大气层中的原子和分子。在这些碰撞中传递的一些能量以光的形式释放出来，这就是极光的表现。极光具有令人着迷的丰富结构（水平尺度可达数十米），具有快速运动和颜色变化。这种结构表明能量沉积到高层大气中的方式发生了快速变化。这种精细尺度结构化的原因尚不清楚，理解原因是本研究的目标之一。我们将使用南安普顿大学在北极运行的极高分辨率极光相机，并将这些观测结果与最先进的模拟结果进行比较，从而研究极光的结构过程。这些相机被称为ASK（极光结构和动力学），通过在大约5x 5公里（100公里高度）的帧中提供极光的高时间和空间分辨率图像，我们可以将极光的分辨率降低到10米。ASK由三个摄像头组成，它们在不同的波长下提供相同的图像。通过比较不同波长下的图像，我们可以收集有关激发极光的沉淀粒子能量的信息，并计算有关局部细尺度电离层流动的信息。这些参数然后被用来作为输入的理论模型，这使我们能够确定的过程，引起极光structuring.In项目的后半部分，我们还将利用第一个数据从一个新的国家的最先进的雷达系统称为EISCAT_3D，它提供了观测的雷达模拟的极光结构，我们将检查在一个空间尺度上接近ASK本身。EISCAT_3D是目前正在建造的一个重要的新欧洲设施;它的“第一束光”将于2022年出现。极光的结构表明了电场和电流的基本结构，这些结构具有一些重要的后果，例如导致高层大气加热速率的变化，这反过来又对气候变化建模和卫星轨道衰减预测产生影响。因此，带电粒子沉降的空间和时间可变性是高层大气行为物理学的核心。

The beautiful displays of the Earth's auroras are formed as a result of the interaction between the solar wind, the Earth's magnetic field and the atmosphere. Electrically charged particles are funnelled into the atmosphere, where they hit atoms and molecules in the atmosphere. Some of the energy transferred in these collisions is given off as light, which is what provides the auroral displays.The aurora is fascinatingly rich in structure (down to horizontal scale sizes of tens of metres), with fast motions and changes of colour. This structure is indicative of rapid changes in the way that energy is deposited into the upper atmosphere. The cause of structuring at such fine scales is unclear, and understanding the cause is one of the objectives of this research. We will investigate the structuring processes in the aurora by using very high resolution auroral cameras which the University of Southampton operates in the Arctic, and comparing these observations with state-of-the-art simulations. The cameras are called ASK (Auroral Structure and Kinetics), and by providing high time and spatial resolution images of the aurora in a frame approximately 5x5 km (at 100 km altitude), we can image the aurora down to a resolution of ~10m. ASK consists of three cameras which provide the same image at different wavelengths. By comparing the images at different wavelengths, we can glean much information about the energy of the precipitating particles which are stimulating the aurora, and calculate information about the local fine-scale ionospheric flows. These parameters are then used as input to theoretical models, which allow us to determine the processes which give rise to auroral structuring.In the second half of the project we will also exploit the first data from a new state-of-the-art radar system called EISCAT_3D, which provides observations of the radar analogues of the auroral structure we will examine on a spatial scale approaching that of ASK itself. EISCAT_3D is a major new European facility which is currently being built; its 'first light' will occur in 2022.The structuring of the aurora indicates underlying structuring of electric fields and currents which have a number of important consequences, such as causing changes to the rate at which the upper atmosphere is heated, which in turn has implications for modelling of climate change and prediction of satellite orbit decay. Therefore, the spatial and temporal variability of precipitating charged particles is at the heart of the physics of the behaviour of the upper atmosphere.