A new method for the calculation of the linear charge density and current in upward positive leader

A new method for the calculation of the linear charge density (LCD) and current in upward positive leader (UPL) is put forward in this study. It is tested in three classical artificially triggered lightning discharges. The current calculated based on the charge density and the velocity of the leader are compared with the measured current, relative brightness of the leader channel in the frame of high-speed camera and some current waveforms reported by other authors. The results indicate that before the disintegration of the wire, LCDs in UPLs are of magnitude from several to hundreds of micro-coulombs per meter and the distribution of LCD was strongly skewed toward the UPL tips. Additionally, the calculated current in the UPLs are of magnitude from less than one to tens of amperes and increase with the leader propagating. The method is believed to be reliable through the analysis and compare.