Fundamental Photographic Observations of Triggered Lightning

这项研究的目的是获取和分析1997年夏天在佛罗里达州布朗德营获得的高时间分辨率闪电触发闪电的摄影记录。所获得的数据将允许研究1)通道创建过程，2)回程和省道前导直径随时间的发展，以及3)通道微尺度曲折的演变。这些实验将产生独特的数据集，这些数据集从根本上说是新的，可能对测试新出现的闪电放电不同阶段的模型至关重要。拟议的录音将在两个不同的地点进行。一个遥远的地点(约1公里外)将被用来提供沿云底以下大部分通道传播的发光闪电分量的总体记录。此外，亦建议在近距离摄影地点(80米外)记录闪电通道在放电过程中演变的新细节。所获得的全部摄影记录将与参与这项运动的其他研究人员将同时获得的其他数据集相互关联并相互补充。远距离记录将记录最初的先导过程使用近紫外线摄影系统创建闪电通道的过程；这提供了对放电初始阶段的出色呈现。近地点的实验将提供相同行程的闪电通道横截面的高时间分辨率图像，这些记录是从仅8毫米范围的垂直截面获得的。这些近距离记录将产生小至6 mm的发光通道直径的直接测量，时间分辨率为0.9ms。一旦获得10-20个回程图像，将尝试从高处的通道部分成像向下传播的省道导轨或省道阶跃导轨的横截面，因为以前没有直接检查省道导轨的发光直径。同一视场的成帧照片(4000 fr/秒)将记录微尺度(~2厘米)上的通道的运动和几何变化。预计在支助的第一个夏季期间，可以在一次实地活动中获得实地观测数据。该项目的其馀部分将专门用于分析摄影数据本身，并将这些结果用于与其他研究人员的协作分析。

Idone/Abstract The objective of this research is the acquisition and analysis of highly time-resolved photographic records of triggered lightning flashes to be obtained during the summer of 1997 at Camp Blanding, Florida. The data acquired will allow study of 1) the channel creation process, 2) the development of the return stroke and dart-leader diameter with time, and 3) the evolution of channel microscale tortuosity. These experiments will yield unique data sets that are fundamentally new and that could be critical in the testing of newly emerging models of different phases of the lightning discharge. The recordings proposed would be made from two separate sites. A distant site (~ 1 km away) would be used to provide an overall record of the luminous lightning components propagating along most of the channel below cloud base. A "near photographic site (80 m away) is also proposed to record new details of the evolution of lightning channels during the course of the discharge. The totality of photographic records obtained would correlate with and complement other data sets to be acquired simultaneously by other researchers participating in this campaign. The distant-site recordings would document the creation of the lightning channel by the initial leader process using a near-UV photographic system; this provides a superior rendering of the initial phase of the discharge. The near-site experiments would provide highly time-resolved imagery of the cross-sections of lightning channels for the same strokes, these records being attained from a vertical section only 8 mm in extent. These close-up recordings would yield a direct measurement of the luminous channel diameter as small as 6mm with a time resolution of 0.9 ms. Once 10-20 return stroke images are obtained, attempts would be made to image the cross-sections of downward propagating dart-leaders or dart-stepped leaders from a channel section aloft as the dart-leader luminous diameter has not been examined directly before. Framing photographs (4000 fr/sec) of the same field of view would document the movement and geometric variation of the channels on the microscale (~2 cm). It is anticipated that the field observations could be acquired in a single field campaign during the first summer of support. The remainder of the project would be devoted to analysis of the photographic data in its own right along with use of these results in collaborative analyses with other researchers.