Return-Stroke Field Close to the Channel with Finitely Conducting Earth

The return-stroke field is one of the severest sources of natural EMI for electrical systems. The return-stroke field affects not only the electrical systems on the ground but also a flying aircraft or a device buried in the soil. Therefore, it becomes necessary to characterize the field. Measurement of return-stroke stroke field is a complicated and expensive exercise, and therefore, researchers often opt for theoretical modeling. In most investigations available in the literature, the field observations are restricted to a few meters above the ground, so the overall field structure in the air is not available. In this work, the spatio-temporal variation of the overall field structure (up to 1 km above the ground) close to the channel (< 1000 m) is investigated with a suitable return-stroke model in the presence of finitely conducting soil for flat ground and a mountain-like structure. A similar endeavor is hard to find in the literature and is expected to provide a valuable understanding of the field close to the channel. As most electrical and electronic devices are placed very close to the air-soil interface, a detailed analysis of the temporal variation of the field in the air close to the ground for different radial distances will also be presented.