The current variation along the discharge channel in cloud-to-ground lightning

Abstract The spectra of cloud-to-ground lightning return strokes channels are obtained by a slit-less high-speed spectrograph. Based on the positive correlation between discharge current and the intensity of ionic lines in the spectra, variation characteristics of return stroke current along the discharge channel are investigated. The result shows that there are three types of the variation trend for discharge current with the increase of height along the channel, they are exponential attenuation, linear attenuation and basically unchanged, respectively. The attenuation factor is roughly positive correlated with the discharge intensity. During strong discharge process the current tends to decay exponentially. In addition, during return stroke process, the current attenuation gradually flattens with time.