FDTD analysis of lightning electromagnetic pulses considering topography and presence of grounded strike object

Azimuthal magnetic fields at a relatively far distance (50 km), generated by a lightning strike to the top of mountain and to the top of an 80-m-high grounded object located on the top of mountain, have been analyzed using the 2D finite-difference time-domain (FDTD) method in the cylindrical coordinate system. Also, the influence of the presence of a mountain range located between the lightning strike point and field observation point on the azimuthal magnetic field has been studied. Azimuthal magnetic fields associated with lightning strike to the top of mountain are higher than those associated with the corresponding strike to a flat ground for both fast- and slow-front lightning currents. The presence of an 80-m-high strike object further increases magnetic field peaks for higher ground conductivity (≥ 1000 mS/m) and shorter current risetime (≤ 1 μs). The field enhancement for the case of lightning strike to a mountain decreases with decreasing the ground conductivity. The shielding effect due to a 1-km-high mountain range located between the lightning strike and observation points is insignificant for relatively-slow-front currents.