Collaborative Research: CEDAR--High Time-Resolution Sprite Imaging

这项研究的科学目标是确定精灵形成的过程，精灵如何适应更大的流光发展领域，以及精灵对中层大气的影响。为了实现这一目标，该项目将使用地面高速相机以前所未有的高时间分辨率拍摄它们的空间和光谱发展。精灵是在雷暴上方看到的大型(约50公里垂直尺度)发光事件，通常延伸到电离层高度。大多数精灵与云对地闪电的正面撞击有关，光发射的持续时间从几毫秒到几10‘S几毫秒。精灵从70-80公里的高度开始，向下传播流光头。在一些事件中，也可以观察到向上移动的流光头部，但向上移动的流光总是比向下的流光开始得晚，而且它们是从较低的高度和精灵体内现有的亮点开始的。之前资助的研究表明，精灵的发育基本上有两个阶段：活跃的初始阶段，其特征是流光头快速移动，随后是衰减阶段，在此阶段几乎没有空间活动。这项分析工作将在该项目下继续进行，并通过使用新的高速成像仪进行观测，以高时间和空间分辨率记录精灵。无狭缝光谱还将用于获得约500米高度、0.1ms(或可能更低)的时间分辨率和10 nm(400-800 nm)光谱分辨率的精灵光谱。为了获得高空间分辨率，将使用望远镜来获得3m的空间分辨率，可能还有100%的S时间分辨率。该计划将包括使用一个流动地面站来进行三角测量。每年将开展一次实地活动。这些观测预计将提供具有前所未有的时间、空间和光谱分辨率的新图像，这将有助于提供对精灵沉积到中间层的能量和电荷量的真实估计。该项目的更广泛影响包括支持一名全日制研究生，他们将接受适合博士论文的观察和理论工作培训。来自空军学院的本科生将参与基础数据的收集和分析。该项目可以间接地将高帧速率图像的使用扩展到电离层、热层和中间层社区。这些观测将提供给精灵社区，从而为各种精灵和流光理论提供基本的观测约束。

The scientific objective of this study is to determine the processes involved in the formation of sprites, how sprites fit into the larger field of streamer development, and the consequences of sprites on the middle atmosphere. To accomplish this goal, the project will use ground-based high speed cameras to image their spatial and spectral development with unprecedented high temporal resolution. Sprites are large (~50km vertical scale size) luminous events seen above thunderstorms often extending to ionospheric heights. Most sprites are associated with positive cloud to ground lighting strikes, and the optical emissions last only from a few milliseconds to a few 10's of milliseconds. Sprites start at 70 - 80 km altitude with downward propagating streamer heads. In some events upward moving streamer heads are also observed, but upward moving streamers always start later than the downward streamers and further, they start from a lower altitude and from existing bright spots in the sprite body. Previously funded research has shown sprite development to have essentially two phases: an active initial phase characterized by fast moving streamer heads followed by a decay phase in which there is little spatial activity. This analysis work will continue under this project and be augmented by observations taken with new high-speed imagers to record sprites with high temporal and spatial resolution. Slit less spectroscopy will also be used to obtain sprite spectra with ~500m altitude, 0.1 ms (or possibly less) temporal and 10 nm spectral (400-800 nm) resolution. For high spatial resolution a telescope will be used to obtain 3m spatial and possibly 100 s temporal resolution. The program will include use of a roving ground station to allow for triangulation. One field campaign per year will be undertaken. The observations are expected to provide new images with unprecedented temporal, spatial, and spectral resolution, which will aid in providing realistic estimates of the amount of energy and charge deposited into the mesosphere by sprites. The broader impacts of the project includes support of one full-time graduate student who will receive training in both observational and theoretical work suitable for a Ph.D. thesis. Undergraduate cadets from the Air Force Academy will participate in gathering and analysis of the basic data. The project may indirectly extend the use of high frame rate imagery to the ionosphere, thermosphere, and mesosphere community. The observations will be made available to the sprite community, thus providing fundamental observational constraints on the various sprite and streamer theories available.