In this paper, we study the effect of overhead shielding wires on the lightning-induced voltages of two typical multiconductor lines configurations at distances from 50 to 1000 m from the lightning channel, considering perfect and lossy ground, respectively, by using the 2-D finite-difference time-domain method and Agrawal field-line coupling model. The results show that the effect of overhead shielding wires on the lightning-induced voltages is closely related to the finite ground conductivity (σ) and the observation distance (d) from the lightning channel. For the ground conductivity ranging from 0.1 to 0.001 S/m, the values of shielding factor (SF) range about from 0.7 to 0.8 for vertical configuration, and range about from 0.6 to 0.7 for horizontal configuration, within distances from 50 to 1000 m from the lightning channel. Also, we have compared the SF values predicted by using Rusck simplified formula with ours in this paper, and it is noted that the Rusck simplified formula underestimates the SF values and the errors may be above 10% under poor ground conductivities of 0.001 S/m when distances larger than 500 m.

This paper presents the computed lightning-radiated vertical electric field and azimuthal magnetic field at the ground level at observing distances ranging from 0.3 to 50 km from the lightning channel for striking the cone-shaped mountain top, by using the two-dimensional finite-difference time-domain method in cylindrical coordinate systems. It is found that the mountain height and the inclination angle have a significant effect on the lightning-radiated electromagnetic field both for the close and far observing distances. For the lightning-radiated vertical electric field, the enhancement of the far field beyond several kilometers (mainly radiation field component) is due to the reflection process in the transition between the mountain terrain and the flat ground, but the reduction of close field near the mountain terrain (mainly quasi-electrostatic field component) is due to the shadowing effect, but not due to such reflection. For the lightning-radiated azimuthal magnetic field, the field values for different mountain terrains, including the mountain height and inclination angle, increase both for close and far observing distances.

This paper evaluates the lightning-induced voltages of two typical multiconductor lines configurations with or without shielding wires over lossy ground for striking the cone-shaped mountain top, by means of a cylindrical two-dimensional finite-difference time-domain method and Agrawal coupling model. It is found that the lightning-induced voltages both for the vertical and the horizontal configurations can be enhanced obviously for striking to the cone-shaped mountain, compared with the case of flat terrain, especially for the lower finite ground conductivity. The larger mountain inclining angle results in the higher peak values of lightning-induced voltages, which can be explained by the enhancement of lightning electromagnetic fields due to wave reflection of the transition between mountain terrain and flat ground. Moreover, the shielding wires can effectively reduce the voltages induced at both ends of the phase lines.

This paper analyzes the effect of lightning strikes to an oblique cone-shaped mountain on the lightning-induced voltages on the power distribution line. The lightning-generated electromagnetic fields are calculated by using a three-dimensional finite-difference time-domain method in Cartesian coordinates, and the lightning-induced voltages are computed by means of Agrawal coupling model. The simulation results are presented for an oblique cone-shaped mountain with different inclining angles, and for different relative positions of the distribution line placed over nonflat lossy terrain. It is found that, when lightning strikes the top of an oblique cone-shaped mountain, the lightning-induced voltages are closely related with the mountain inclining angles where the distribution line is located above as well as the other mountain inclining angles; in general, the peak values of induced voltages increase with increasing inclining angles. For example, for the constant angle β = 45° (the inclining angle where the line is located above), the induced voltages at the close end of line for α = 26.6°, 45°, and 63.4° (the inclining angle opposite to angle β) is increased by 24%, 60%, and 106% as compared with that for flat ground, respectively.

Sprite halos are transient luminous phenomena in the lower ionosphere triggered by tropospheric lightning. The effect of removed charge distributions on sprite halos has not been sufficiently discussed. A three-dimensional (3D) quasi-electrostatic (QES) field model was developed in this paper, including the ionospheric nonlinear effect and optical emissions. Simulation results show that, for a total charge of 150 C removed within 1 ms with different spatial distributions, higher altitudes of charge removal lead to stronger electric fields and increase sprite halos’ emission intensities. The non-axisymmetric horizontal distribution of charge affects mesospheric electric fields, and the corresponding scales and intensities of emissions vary with observation orientations. Considering the tilted dipole charge structure due to wind shear, the generated electric field and the corresponding position of sprite halos shift accordingly with the tropospheric removed charge, providing an explanation for the horizontal displacement between sprite halos and the parent lightning.

Sprite halos are diffuse glow discharges in the D-region ionosphere triggered by the quasi-electrostatic (QES) fields of lightning discharges. A three-dimensional (3D) QES model is adopted to investigate the effect of ionospheric electron density on sprite halos. The electron density is described by an exponential formula, parameterized by reference height (h’) and sharpness (β), and the local inhomogeneity has a Gaussian density distribution. Simulation results indicate that the reference height and steepness of the nighttime electron density affect the penetration altitudes and amplitudes of normalized electric fields, as well as the altitudes and intensities of the corresponding sprite halos optical emissions. A comparison of the daytime and nighttime conditions demonstrates that the daytime electron density profile is not favorable for generating sprite halos emissions. Furthermore, the pre-existing electron density inhomogeneities lead to enhanced local electric fields and optical emissions, potentially offering a plausible explanation for the horizontal displacement between sprites and their parent lightning, as well as their clustering.