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

同时测量雷电流及其相关的电场和磁场，并确定闪电通道特性是必要的定量评估雷击回击模型。这样的评估将提高我们对雷击回击过程的理解，有助于制定新的模型，这些模型可以更成功地用于雷电探测算法，并允许开发更复杂的雷电防护措施。同时测量雷电流及其辐射的电磁脉冲是可能的，使用仪器化的高大结构，或火箭或激光触发的闪电。加拿大国家电视塔，以其极端的高度，提出了一个最好的选择在世界上进行这项调查。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年夏季开始时，五个测量站已投入运行，同时捕获了所有相关的闪电参数，包括雷电流导数及其相关的电磁场。许多雷电回击电流模型已被评估的基础上无关的统计信息的雷电流和雷电产生的电磁场;显着的例外包括使用仪表塔或火箭触发的闪电。在拟议的项目中，将对这一瞬态电磁场问题进行详细和严格的分析，目的是开发一个更可通过实验验证的回程模型。虽然CN塔的闪电大多是向上引发的类型，但向下引发的闪电类似于普通的地面闪电，在塔上也观察到了。因此，开发的模型可以使用两种类型的照明进行评估。在目前的模式中，假设闪电通道是直的和垂直的，与大多数观测相反。在本项目中，将从视频记录中构建闪电通道的三维图像，并将其与测量的（取决于高度的）回击速度一起用于开发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.