Full-wave modeling of early VLF perturbations caused by lightning electromagnetic pulses

We use the three-dimensional full-wave method and Born approximation technique to calculate the scattered VLF field in the near zone of ionospheric disturbances created by lightning electromagnetic pulses. The method fully accounts for the anisotropicity of the ionosphere magnetized by a nonvertical geomagnetic field. We calculate the VLF amplitude perturbation on the ground for vertical and horizontal lightning discharge configurations. The results show that the magnitude of the scattered signal is strongly dependent on the direction of the incident VLF wave.