Abstract
The radial fine structure of lightning channels is crucial for understanding the physical mechanisms of lightning discharge, energy transmission, and lightning protection effects. Traditional theoretical models suggest that lightning channels consist of a high-temperature and high-conductivity core carrying axial current and a corona sheath layer storing charges. In recent years, with the development of high-speed optical imaging, slitless spectroscopy, and near-field electrical measurements, researchers have directly observed the visible channel core in natural lightning for the first time and obtained key parameters such as the radial temperature and conductivity distribution of the channel. This paper systematically reviews the research progress in the radial structure of lightning channels in terms of theoretical models, observational diagnostics, and parameter characteristics, confirming the rationality of the corona sheath model and revealing significant differences in physical properties between the channel core and the corona sheath. Current research is moving from macroscopic models to direct diagnosis of microscopic physical parameters, but key issues such as the formation and evolution mechanism of the channel core, the precise quantification of sheath currents, and the dynamic changes in radial structure at different discharge stages remain unsolved. Future research opportunities lie in multi-platform collaborative observations, the application of high-resolution diagnostic techniques, and the construction of multi-physics field coupling models, while challenges include the extreme difficulty of observations, the uncertainty in parameter inversion, and the deep integration of theoretical models with experimental data.