Modeling of LEMP propagation in the lossy atmosphere

The finite-difference time-domain (FDTD) method in the 2D cylindrical coordinate system was used to compute waveforms of nearly full-frequency-bandwidth vertical electric field E
_z
and azimuthal magnetic field H
_φ
produced on the ground surface by lightning return strokes. The conductivity of atmosphere was assumed to increase exponentially with height, with different conductivity profiles being used for daytime and nighttime conditions. The fields were computed at distances ranging from 100 to 500 km. Positive and negative parts of skywaves (reflections from the ionosphere) were identified in computed waveforms and used for estimation of apparent ionospheric reflection heights.