Temperature distribution and evolution characteristic in lightning return stroke channel

•Temperatures of core and outside optical channels are studied by different methods.•Radial temperature distribution along the channel at peak current time is discussed.•The temperature evolution with time in return stroke process is investigated.

According to the time-resolved spectra of four lightning return strokes, the temperatures of arc core channel and the peripheral optical channel surrounding the arc core are investigated by different methods; the temperature distribution along the radial direction of channel on the peak current stage is discussed. The results show that a temperature gradient is formed along the radial direction of channel during the discharge process. With the increasing of the radius, the temperature decreases gradually. The temperature of arc core channel is about 4000–5000 K higher than that of the peripheral optical channel. The time evolution of channel temperature shows that the falling of the temperature is very slow compared with the decreasing of the current after their peak values. After the peak current, the channel temperature is still maintained at around 20,000 K up to 200–400 μsμs. The heat effect resulting from such a long-time high temperature is the main source of most direct lightning disasters.