Some new observations of lightning spectra in the bands above 25 MHz

Lightning spectra in the frequency bands above 25 MHz were examined for some specific lightning events: preliminary breakdown processes, downward negative leaders, return strokes, K changes, and upward positive leaders. The spectra were obtained by means of the Fourier transformation of wideband records of electromagnetic fields from lightning. Results show that the lightning spectra in the HF bands are closely related to the developing stage. The spectrum for an event within the cloud tends to peak near 60 MHz, while that for an event outside the cloud does not. Such dissimilarity in the spectra provides a basis for identifying different lightning events.