Collaborative Research: CEDAR: Sprite Energetics

这项研究的目的是确定在中间层中沉积的能量精灵的数量。精灵是在雷暴上方可以看到的大型(约50公里尺度)发光事件。研究人员将在毫秒和更高的时间分辨率上进行高度分辨光谱。观测结果将确定精灵如何改变中间层。大多数精灵与积极的云对地闪电撞击有关，光度可能从云顶延伸到电离层高度。精灵持续几毫秒到10‘S毫秒，通常在70-75公里的高度启动，然后是光度的向上和向下传播。精灵以红色为主，但低海拔的卷须是蓝色的。在电视帧速率(33ms分辨率)下的光谱测量表明，发射来自分子氮。预计会有来自电离氮的蓝色发射，但这一点尚未得到证实。到目前为止，现有的数据还不能确切地回答核心问题，即有多少能量被沉积到中间层，以及由此产生的精灵对中间层的修改。为了解决精灵中能量沉积的时间发展问题，研究人员将进行毫秒时间分辨率的光谱观测。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通道多阳极光谱测光仪，以及一个电视成像器来提供空间背景。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，还将在单独的位置部署成像仪，以提供三角测量的高度信息。这些测量将与精灵发射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由此导致的中间层电导率的变化。计划了两次扩大的地面行动。这项研究将对雪碧的形成和繁殖作为时间和海拔的函数提供清晰的理解。光谱测量将提供来自精灵的中性和电离氮排放的明确记录。将本项目获得的数据与精灵发射模型进行比较，将提供精灵能量学的时间历史。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。该研究计划还包括来自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第一手的真实研究机会，希望他们对研究生水平的进一步学习感兴趣。此外，调查人员还计划针对高中生和教师开展一项强有力的外展计划。

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.