DRivers and Impacts of Ionospheric Variability with EISCAT-3D (DRIIVE)

在支撑空间天气研究的日地科学中，最大的未回答的问题之一是：高纬度电离层如何在小尺度上变化，以响应从上方和下方的驾驶？一个直接的实际后续问题是：小规模进程对更大的高层大气环境有哪些影响？这些问题的答案对于理解空间气象如何影响社会至关重要。这一领域对联合王国的重要性日益增加，气象局最近对空间气象业务预报的投资以及将空间气象列入国家风险登记册就是证明。为了回答这些问题，我们需要了解在被称为中间层-低热层-电离层（MLTI - 75-200公里高度）的区域发生的过程，以及它们如何影响更广泛的耦合电离层-高层大气系统。电离层和高层中性大气有着内在的联系：扰动一个，另一个就会发生变化。这对我们的近地空间环境产生了影响，在近地空间环境中，大气密度的变化导致空间碎片轨道的变化，增加了发生意外碰撞的风险;随着地球空间变得越来越拥挤，这是一种重大的自然灾害。空间天气通过摩擦焦耳加热和粒子能量沉积在改变这一区域方面发挥着重要作用，但不是唯一重要的驱动因素。低层大气中的天气驱动电离层的变化，这种变化可以与外部强迫相比较，但由于对这些过程的观测不足，因此其相对贡献还远未得到理解。了解这种贡献的另一个障碍是我们无法正确地解释小规模的变化，无论是从上面还是下面驱动的。高层大气模型通常不能解决这种变化，但我们知道，不这样做会导致低估大气加热的幅度高达40%。这种加热是一个既依赖于空间天气驱动又依赖于中性大气成分和动力变化的过程。该项目将使用全新的下一代电离层雷达：EISCAT-3D，位于芬诺斯坎迪亚北方。这部分由NERC资助。它能够对大量的局部电离层成像，并提供1-100公里水平尺度的测量。它将是独一无二的，具有高垂直和时间分辨率以及电离层电场矢量的多点测量。雷达的视野将覆盖相当大比例的极光带纬度，因此在那里进行的测量结果可以应用于更广泛的区域。我们将利用雷达的独特能力来量化空间天气事件中沉积到MLTI中的能量，并测量从低层大气向上传播的小尺度波的影响。我们将使用一系列支持仪器，包括新部署的光学器件，并确定中性和电离状态之间的耦合如何影响能量平衡。解决这些过程将使我们能够确定它们在高层大气加热中的作用。我们将使用E3 D观测和综合高层大气模型来确定和应用由于小尺度变化而校正加热估计的方法。我们将利用先进的模型，并根据我们的观测结果提供投入，确定小尺度如何影响地球外部环境中的低空卫星碎片场。该项目直接解决了NERC亮点主题机会公告中确定的两个优先领域（并触及其他领域），因此回答了关键问题：高纬度电离层如何在小尺度上变化，以响应从上方和下方驾驶？

One of the biggest unanswered questions in the solar-terrestrial science that underpins Space Weather research is: How does the high latitude ionosphere vary on small scales in response to driving from above and below? An immediate practical follow-on question would be: what are the impacts of small-scale processes to the larger upper atmosphere environment? The answers to these questions are essential for understanding how Space Weather impacts on society. This area is of growing importance to the UK, as evidenced by recent investment in operational Space Weather forecasting at the Met Office and the inclusion of Space Weather in the National Risk Register. To answer these questions, we need to understand the processes that occur in the region known as the Mesosphere-Lower Thermosphere-Ionosphere (MLTI - 75-200 km altitude) and how they affect the wider coupled ionosphere-upper-atmosphere system. The ionosphere and upper neutral atmosphere are intrinsically linked: perturb one and the other changes. This has implications for our near-Earth space environment where variations in atmospheric density produce changes in the orbits of space debris, increasing the risk of unforeseen collisions; a significant natural hazard as Geospace grows more crowded. Space Weather plays a big role in modifying this region through frictional Joule heating and particle energy deposition but is not the only important driver. The weather in the lower atmosphere drives changes in the ionosphere that can be comparable to external forcing, but the relative contribution is far from understood, as the processes are under-observed. Another barrier to knowing that contribution is our inability to properly account for small scale variability, whether driven from above or below. Upper atmosphere models typically do not resolve this variability, yet we know that not doing so leads to underestimates of the magnitude of atmospheric heating by as much as 40%. This heating is a process that relies both on space weather driving and changes in the neutral atmosphere composition and dynamics. This project will use the brand new, next generation ionospheric radar: EISCAT-3D, located in northern Fennoscandia. This is part funded by NERC. It is capable of imaging a large volume of the local ionosphere and providing measurements on horizontal scales of 1-100 km. It will be unique with high vertical and temporal resolution and multipoint measurements of the ionospheric electric field vector. The field of view of the radar will cover a decent proportion of the auroral zone in latitude, such that results from the measurements made there can be applied to the wider region. We will use the unique capabilities of the radar to quantify the energy that is deposited into the MLTI from space weather events and also measure the impact of small-scale waves that propagate upwards from the lower atmosphere. We will use a range of support instrumentation, including newly deployed optics, and determine how the coupling between the neutral and ionized regimes affect the energy balance. Resolving these processes will let us establish their role in upper atmospheric heating. We will use the E3D observations together with comprehensive upper atmosphere models to determine and apply methods of correcting estimates of heating due to the small-scale changes. Using advanced models with inputs informed by the results of our observations we will determine how the small-scales affect the low altitude satellite debris field in the Earth's outer environment. This Project directly addresses two of the priority areas (and touches on others) that have been identified in the NERC Highlight Topic Announcement of Opportunity, and so answers the key question: How does the high latitude ionosphere vary on small scales in response to driving from above and below?