Fig. 1. The original spectra of lightning return stroke channels

Fig. 2. The spectra of lightning return stroke channels at a given height
(a): The spectra of first return stroke R1; (b): The spectra of subsequent return stroke R2; (c): The spectra of subsequent return stroke R3; (d): The spectra of subsequent return stroke R4

Fig. 3. The luminous radius of lightning return stroke channels at a given height by luminous pixels
(a): R1 passagway; (b): R2 passagway; (c): R3 passagway; (d): R4 passagway

Fig. 4. The waveform of fast electric field change caused by lightning
(a): R1 passagway; (b): R2 passagway; (c): R3 passagway; (d): R4 passagway

Fig. 5. Correlation analyses
(a): Correlation analysis between the conductivity and the peak power per unit lenth;(b): Correlation analysis between the return stroke speed and the peak pwoer per unit lenth;(c): Correlation analysis between the initial electric field peak and the peak pwoer per unit lenth;(d): Correlation analysis between the peak current and the peak pwoer per unit lenth

Table 1. The basic parameters of lightning return stroke

Table 2. The characteristic parameters of the lightning return stroke channel core