Computation of electromagnetic fields radiated by lightning strikes to the Toronto CN Tower

grantor: University of TorontoWith an important number of engineering applications, the computation of the electromagnetic field radiated from cloud-to-ground lightning is, presently, a major area of research. Taking advantage of the comprehensive simultaneous measurements (derivative of current, azimuthal and radial magnetic field, vertical electric field, video records) collected for lightning flashes striking the Toronto CN Tower, the principal factors that affect the computation accuracy of electromagnetic fields surrounding a tall structure are investigated. Models and analytical relations describing accurately the return stroke current for lightning flashes striking the Toronto CN Tower were developed. These models were integrated into new field computation algorithms. Computed azimuthal magnetic fields with these new algorithms are compared with the measured fields. This comparison gives conclusions that contribute to better understanding of the specifics of lightning striking tall structures. Two significant and original contributions to the improvement of the CN Tower Lightning Project data acquisition systems performances are presented in Appendix A: improvement of time stamping accuracy for the acquired waves and reduction of the transfer time of data from digitizers to hard disks.M.A.Sc