Evaluation and development of lightning return-stroke models at elevated objects

同时测量雷电电流及其相关的电场和磁场，以及确定闪电通道特性，对于雷电回击模型的定量评估是必要的。这种评估将加强我们对闪电回击过程的了解，有助于制定可更成功地用于闪电探测算法的新模型，并使我们能够制定更复杂的雷电保护措施。同时测量闪电电流及其辐射的电磁脉冲是可能的，使用仪器的高层结构，或火箭或激光触发的闪电。CN塔具有极高的高度，是世界上进行这项调查的最佳选择之一。这一事实导致了CN塔闪电研究的一个重要阶段的开始。到1991年夏季初，五个测量站投入使用，以同时捕获所有相关的闪电参数，包括闪电电流导数及其相关的电磁场。许多闪电回击电流模型都是根据与闪电电流和闪电产生的电磁场无关的统计信息进行评估的；值得注意的例外包括使用仪表塔或火箭引发的闪电。在拟议的项目中，将对这个瞬变电磁场问题进行详细和严格的分析，目的是开发一个更能在实验上验证的回击模型。虽然CN塔的闪电大多是向上闪电，但也有类似于普通地面闪电的向下闪电。因此，所开发的模型可以使用这两种类型的飞行进行评估。在目前的模型中，假设闪电通道是直的和垂直的，这与大多数观测结果相反。在这个项目中，除了测量的(与高度相关的)回击速度外，还将从视频记录中构建闪电通道的三维图像，用于开发经过实验验证的闪电回击模型。

Simultaneous measurement of the lightning current and its associated electric and magnetic fields, and thedetermination of lightning channel characteristics are necessary for the quantitative assessment of lightningreturn-stroke models. Such assessments will enhance our understanding of the lightning return-stroke process,help in the formulation of new models that can be more successfully used in lightning detection algorithms, andpermit the development of more sophisticated measures for lightning protection. Simultaneous measurementsof the lightning current and its radiated electromagnetic pulse are possible using instrumented tall structures, orrocket- or laser-triggered lightning. The CN Tower, with its extreme height, presents one of the best options inthe world to carry out this investigation. This fact led to the initiation of an important phase of the CN Towerlightning studies. By the start of the summer of 1991, five measurement stations were operational tosimultaneously capture all relevant lightning parameters including the lightning current derivative and itsassociated electromagnetic field. Many lightning return-stroke current models have been evaluated on the basisof unrelated statistical information about lightning currents and lightning-generated electromagnetic fields;notable exceptions include the use of instrumented towers or rocket-triggered lightning. During the proposedproject, a detailed and rigorous analysis of this transient electromagnetic field problem will be carried out withthe aim of developing a more experimentally verifiable return-stroke model. Although CN Tower lightningflashes are mostly of the upward-initiated type, downward-initiated flashes, similar to ordinary ground flashes,have been observed at the tower. Therefore, the developed model can be evaluated using the two types oflighting. In present models, it is assumed that lightning channels are straight and vertical, contrary to mostobservations. In this project, a three-dimensional image of the lighting channel will be constructed from videorecords and used, in addition to the measured (height-dependent) return-stroke velocity, for the development ofan experimentally verified lightning return-stroke model.