Narrow bipolar pulses and associated microwave radiation

Abstract

Narrow Bipolar Pulses (NBPs) is a special type of intra-cloud lightning discharge activities and was observed with both polarities: negative (NNBP) and positive (NPBP). It is known with other names also such as Narrow Bipolar Events (NBEs), energetic intracloud events, and Compact Intracloud Discharges (CIDs). NBP signatures have been measured by using various methods such as electric field change recording systems, HF-VHF direct measurement systems (filter-detector receiver), and satellite-based systems. To the best of our knowledge, there are no attempts have been made to measure NBP signatures at microwave region so far. In this paper, observations of microwave radiation from thunderstorms have been made during the northeastern monsoon season of 2012 in Malaysia. Fast electric field change recording and broadband microwave receiver systems have captured simultaneous records of NBPs electric field change and microwave radiation, respectively. Strong noise-like burst of microwave radiation pulses associated with NBP events were detected. The total duration of the microwave bursts of the pulses is in the range between 2 and 8μs for both NNBPs and NPBPs. More than 70% of the recorded radiation bursts arrived a few microseconds before the onset of the corresponding NBPs. The analyzed temporal characteristics of the microwave radiation bursts for both NNBPs and NPBPs are similar and indistinctive. In contrast, the analyzed NNBPs and NPBPs temporal characteristics are distinctive to some extent.