Electric fields at the top of tall building associated with nearby lightning return strokes

Abstract

Using the finite-difference time-domain (FDTD) method for solving Maxwell’s equations, we have calculated the vertical electric field E z due to lightning return strokes both in the presence and in the absence of building at the field point. Strikes to both flat ground and tall objects of height h=100, 200, or 500 m are considered. The magnitude of E z is significantly influenced by the presence of either building at the field point or strike object. In the case of a lightning strike to flat ground, the magnitude of E z on the roof of building having a plan area of S b =40 × 40 m2 and a height of h b =20, 50, or 100 m located at a horizontal distance ranging from d =100 to 500 m from the lightning channel is about 1.5, 2, or 3 times, respectively, greater than that at the same horizontal distance on the ground surface in the absence of building. The enhancement factor for E z due to the presence of building at the field point is essentially not influenced by the presence of strike object (up to 500 m in height).