Inversion of physical parameters of bipolar narrow pulse discharge in the northeastern Qinghai-Tibet Plateau

The three-dimensional coordinates are calculated by using the synchronous electric field waveform data of narrow bipolar pulse, which are detected at Qinghai region in the northeast of Qinghai-Tibet Plateau. Based on the three different transmission line models and the particle swarm optimization algorithm, we fit the narrow bipolar pulses, and statistically analyze those physical quantities such as current amplitude and the length of the discharge channel. The main results of this paper are as follows: 1) compared with the standard transmission line (TL) model and the modified transmission line model with Kumaraswamy distribution of current (MTLK), the current characteristics fitted with the modified transmission line model (MTLEI) with a current that increases exponentially along the propagation are characterized by longer rising edge time and current duration. Meanwhile, the MTLEI model has the larger current peak range (185.8－837.5 kA) than other two models. 2) Compared with the TL model, the current rising edge time obtained by the MTLK model fitting is longer, the falling edge time is slightly lower, and the duration is longer. The MTLK model fits the parameters obtained for NBEs. In the median value (the peak current is 120 kA, the current channel length is 678 m, and the current speed is 2.05×10⁸ m/s) is slightly larger than the TL Model (the peak current is 94.3 kA, the length of the current channel is 491.1 m, and the current speed is 1.68×10⁸ m/s). However, the MTLK model considers the consumption during current transmission, which is closer to reality. 3) The electric dipole moments obtained by the inversion of the three transmission line models range from 100 to 800 C·m, and the NBE that occurs at a higher position generally has a larger electric dipole moment.