Effect of Mountain Terrain near Lightning Channels on Electric Fields at Sprite Halos Initiation Region

The electric fields generated by lightning discharges propagate upward and couple with the lower ionosphere, triggering various mesospheric optical emissions. The potential role of local terrain in modulating the lightning-generated electric fields in the lower ionosphere remains poorly understood. To investigate the effect of mountain terrain on the lightning-generated electric fields at high altitudes (70–85 km), a two-dimensional (2D) finite-difference time-domain (FDTD) simulation model was developed. The simplified mountain is parameterized by its height, width, and horizontal distance from the lightning channel. Simulation results show that mountain terrain significantly influences the lightning-driven electric field waveforms in the initiation region of sprite halos. Increased mountain height leads to greater attenuation of the high-altitude electric field amplitudes, thereby suppressing sprite halos initiation. The shielding effect of mountain width on the electric fields is less pronounced than that of mountain height, and it stabilizes when the width exceeds 40 km. When the horizontal distance between the mountain and lightning channel is less than 40 km, the electric field attenuation increases significantly with decreasing distance. The attenuation effect gradually weakens beyond a distance of 40 km, yet the electric field waveforms exhibit considerable fluctuations due to the reflection process.