Fine-scale auroral structure: Causes and effects

地球极光的美丽展示是太阳风、地球磁场和大气相互作用的结果。带电粒子被输送到大气中，在那里它们撞击大气中的原子和分子。在这些碰撞中传递的一些能量以光的形式发出，这就是极光的显示。极光具有令人着迷的丰富的结构(精确到几十米的水平尺度)，具有快速的运动和颜色的变化。这种结构表明能量储存到高层大气的方式发生了迅速的变化。结构如此精细的原因尚不清楚，了解其原因是本研究的目的之一。我们将使用南安普顿大学在北极运营的非常高分辨率的极光相机来研究极光的结构过程，并将这些观测结果与最先进的模拟进行比较。这些相机被称为ASK(极光结构和动力学)，通过在大约5x5公里(100公里高度)的帧中提供高时间和空间分辨率的极光图像，我们可以拍摄分辨率为~10米的极光图像。ASK由三个摄像头组成，它们在不同的波长上提供相同的图像。通过比较不同波长的图像，我们可以收集到大量关于刺激极光的降水粒子的能量信息，并计算出关于局部细尺度电离层流动的信息。这些参数然后被用作理论模型的输入，使我们能够确定引起极光结构的过程。在项目的后半部分，我们还将利用来自名为EISCAT_3D的新的最先进的雷达系统的第一批数据，该系统提供了对极光结构的雷达模拟的观测，我们将在接近ASK本身的空间尺度上进行检查。EISCAT_3D是目前正在建造的一个重要的欧洲新设施；它的“第一缕曙光”将出现在2022年。极光的结构表明电场和电流的基本结构，这些电场和电流具有一些重要的后果，例如引起高层大气加热速率的变化，而高层大气的加热速率反过来又导致了对气候变化的模拟和卫星轨道衰退的预测。因此，沉淀带电粒子的空间和时间变异性是高层大气行为物理的核心。

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 hasimplications 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.