High Frequency Radio Emission from a Thundercloud: A Case Study

The results of observation of radio frequency emission from a close thunderstorm of June 22, 2016 are presented. Radio frequency emission from a thundercloud existed on time intervals of a fraction of a second separated by intervals of the same length. The emission was predominantly pulsed with sub-microsecond duration of bipolar pulses separated by time intervals of tens of microseconds, and occurs suddenly showing no gradual development. Emission existed not only during development of lightning discharges, but also in the gaps between them. Two indicators were used to highlite pulsed emission: the ratio of the root mean square and median absolute values, and the kurtosis of the distribution of the received signal at time intervals of a fraction of a millisecond. Statistical characteristics of pulse amplitudes and interpulse intervals are investigated. A possible connection of the observed submicrosecond pulsed radio emission with runaway breakdown caused by the passage of extensive air showers through the region of strong electric field inside thundercloud is discussed.