The bipolar field change pulses produced by intra-cloud lightning discharge processes have been recorded with our observation of lightning. The wave forms are obviously different from those produced by return strokes in cloud-to-ground lightning. Pulses with a positive initial polarity tend to occur at regular interval. Negative pulses are usually produced intra-cloud lightning discharges at more random interval. In this paper, it is shown characteristics of the time components in bipolar pulses.
