Radial Distribution of Physical Characteristics in the Peripheral Corona Sheath at the Peak‐Current Stage of Return Stroke

Abstract The radial distribution of physical characteristics of the lightning return stroke channel is of significant importance for investigating the microscopic mechanism of the discharge process. Based on the spectra of lightning return strokes and the synchronous variations of the ground electric field, in conjunction with plasma transport theory, the radial distributions of temperature, pressure, electron density, conductivity, and particle number densities of the surrounding corona channel at the peak‐current stage of return‐stroke are investigated. The results indicate that the temperature decays logarithmically along the radial direction. Compared with the temperature decay trend, the channel pressure decays more rapidly. The radial distribution of the particle number densities indicates that the electrons in the current‐carrying core channel mainly arise from the primary ionization contributions, and the single‐ionized ions predominate in the core channel. The research further confirms that, during the initial stage of the return stroke, the ionic line emissions mainly originate from the current‐carrying core channels, while the atomic lines mainly derive from the radiation of the surrounding corona sheath. The conductivity diminishes rapidly along the radial direction in a logarithmic relationship to approximately 0.021–0.061 × 10 4 S/m, and then decays slowly in an exponential relationship. The conductivity drops to 10 −12 –10 −13 S/m at the luminous edge of the channel. A larger current‐carrying core channel radius corresponds to both a broader radial extent of high conductivity and a higher peak‐current. There are different mechanisms influencing the magnitude of conductivity: within the high‐temperature core channel, electron density dominates, while in the surrounding corona sheath, it is the synergistic effects of electron density and temperature. The conductivity and its radial decay in the corona sheath have a significant influence on the current intensity of the return stroke discharge.