3. Results and discussions
From 140 cloud discharges and 900 cloud-to-ground discharges recorded, 38 and 101 of them were selected, respectively. Only flashes with detectable first pulse in cloud discharges (Fig.1) or with detectable preliminary pulses in cloud-to-ground discharges were selected for analysis. Since a high resolution (12-bit) recorder was used in this analysis, the noise level was low and this minimized the chances of misinterpreting noise as the first pulse.