Characteristics of return stroke current and electromagnetic field waveforms observed in multistroke lightning flashes to a tall tower

Current and electromagnetic field characteristics of first and subsequent strokes, of lightning flashes striking a tall structure (the Toronto 553-m tall CN Tower), are investigated. Ratios of subsequent to first stroke characteristics of currents and fields are compared for four specific 7- and 8-stroke flashes. In addition to the dependence of field waveform characteristics on features of the return stroke current waveform (peak value, maximum steepness etc.), they are found, in some cases, to depend strongly on other factors, such as the time interval preceding a subsequent stroke. Obtained results may be usefully applied in areas of lightning protection, in operation of lightning location systems, and in planning of future studies of lightning characteristics