抄録
Azimuthal magnetic fields at a far distance (50km), generated by a lightning strike to the top of a mountain and to the top of an 80-m-high grounded object located on the top of a mountain, have been analyzed using the finite-difference time-domain (FDTD) method in the two-dimensional 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 remote azimuthal magnetic field has been studied. Azimuthal magnetic fields associated with a lightning strike to the top of a 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 (≥ 1000mS/m) and shorter current risetime (≤ 1µs). The far-field enhancement due to the presence of a lightning-struck mountain decreases with decreasing the ground conductivity. The shielding effect due to a 1-km-high mountain range located between the strike point and observation point is insignificant except for relatively fast-front lightning currents.
