Collaborative Research: CEDAR: Sprite Energetics

这项研究的目的是确定能量精灵沉积在中间层的数量。精灵是在雷暴上空看到的大型（约50公里大小）发光事件。研究人员将制作毫秒级和更高时间分辨率的高度分辨光谱。观测结果将决定精灵是如何改变中间层的。大多数精灵与云层对地面的正面闪电有关，亮度可能从云层顶部延伸到电离层高度。精灵持续几毫秒（ms）到10毫秒，通常在70-75公里的高度开始，然后向上和向下传播光度。精灵主要是红色的，但在低海拔的卷须是蓝色的。以电视帧率（33毫秒分辨率）进行的光谱测量显示，这些排放物来自氮分子。电离氮的蓝色辐射预计会存在，但这还没有得到证实。到目前为止，现有的数据还不能确切地回答有多少能量沉积到中间层，以及由此产生的精灵对中间层的改变等核心问题。为了解决精灵中能量沉积的时间发展问题，研究者将进行毫秒时间分辨率的光谱观测。在一个公共安装上的主要仪器将是一个成像狭缝光谱仪和两个16通道多阳极光谱光度计，以及一个电视成像仪，以提供空间背景。成像光谱仪将提供更好的光谱分辨率，而光谱光度计将提供更好的时间分辨率。此外，成像仪将部署在一个单独的位置，以提供三角高度信息。测量结果将与精灵排放的第一性原理模型进行比较，以确定能量沉积作为海拔和时间的函数。研究人员还将确定由精灵引起的电离量和中间层内电导率的变化。计划进行两次延长的地面战役。这项研究将使人们清楚地了解雪精灵的形成和传播随时间和海拔的变化。光谱测量将提供精灵中性氮和电离氮排放的明确记录。将该项目获得的数据与精灵排放模型进行比较，将提供精灵能量学的时程。这项研究将提供实验和理论发展的平衡，适合攻读博士学位的学生。该研究计划还包括空军学院的本科生参与光谱光度计的校准，以及数据的收集和分析。这些经历将为本科生提供对真正研究的第一手了解，希望他们在研究生阶段的进一步学习中感兴趣。此外，调查人员还计划针对高中学生和教师开展积极的外展活动。

The objective of this research is to determine the amount of energy sprites deposit in the mesosphere. Sprites are large (~50km scale size) luminous events seen above thunderstorms. The investigators will make altitude resolved optical spectra at millisecond and higher time resolution. The observations will determine how sprites modify the mesosphere. Most sprites are associated with positive cloud to ground lighting strikes, and luminosity may extend from cloud tops up to ionospheric heights. Sprites lasts a few millisecond (ms) to 10's of ms with initiation commonly at an altitude of 70-75 km followed by both upward and downward propagation of luminosity. Sprites are predominantly red, but tendrils at low altitude are blue. Spectral measurements at TV frame rates (33 ms resolution) show the emissions to be from molecular nitrogen. Blue emissions from ionized nitrogen are expected to be present, but this has not been confirmed. The data available so far have not been able to answer firmly the central questions of how much energy is deposited into the mesosphere, and the resulting modification of the mesosphere by sprites. To address the time development of the energy deposition in sprites, the investigators will make spectral observations with ms time resolution. The primary instruments on a common mount will be an imaging slit spectrograph and two 16-channel multi-anode spectral photometers together with a TV imager to provide spatial context. The imaging spectrograph will provide better spectral resolution, while the spectral photometers will provide better temporal resolution. In addition, an imager will be deployed at a separate location to provide triangulated altitude information. The measurements will be compared to first principles models of sprite emissions to determine the energy deposition as a function of altitude and time. The investigators will also determine the amount of ionization and resulting changes in conductivity within the mesosphere caused by sprites. Two extended ground campaigns are planned. This research will provide clear understanding of sprite formation and propagation as a function of time and altitude. Spectral measurement will provide an unambiguous record of the neutral and ionized nitrogen emissions from sprites. Comparison of data obtained from this project with models of sprite emission will provide the time history of sprite energetics. The research will provide a balance of experimental and theoretical development suitable for a student working towards a PhD. The research plan also includes undergraduate cadets from the Air Force Academy in the calibration of the spectral photometers, and the gathering and analysis of the data. These experiences will provide the undergraduates a first hand look at real research, hopefully interesting them in further study at the graduate level. In addition the investigators plan a vigorous outreach program directed at high school students and teachers.