Observation of the Whole Discharge Process During a Multi-stroke Triggered Lightning by Continuous Interferometer

Abstract

The discharge process is often discussed in the lightning physics. VHF (very high frequency) observations play an important role in studying lightning discharge processes, because they show where air breakdown occurs. Triggered lightning flashes are ideal research objects, because they are generated in a fixed time and place. Regular experiments of triggering lightning have been conducted by Chinese Academy of Meteorological Sciences since 2006, and 189 lightning flashes are triggered successfully. Besides regular observations, such as fast/slow antenna, channel-based current and high-speed video, the continuous interferometer (CINTF) is developed and deployed at the site for triggered lightning after 2016 in order to observe detailed discharge processes. The CINTF can provide high-precision location with time resolution of around 1 μs.A multi-stroke triggered lightning with 8 return strokes is observed by a self-developed lightning continuous interferometer during Guangdong Comprehensive Observation Experiment on Lightning Discharge on 11 June 2019. The whole discharge processes, including precursor current pulse, initial precursor current pulse, initial continuous current and return strokes, last for about 1600 ms. The channel-based current, electric field change and radiation source positions are obtained. CINTF results show that the radiation signal generated from discrete precursor current pulse with a minimum value of about 8 A can be detected. The average transfer charge of initial precursor current pulse is twice as much as that of the precursor current pulse. During the initial continuous current stage after continuously developing of the upward positive leader, the obviously forward channel extension is the main discharge form at the beginning, and then the extension can be accompanied by discontinuously backward propagation, and recoil leader often occurs in the following stage. M-component in the ICC stage is caused by two discharge processes:Forward positive streamer (or leader) or recoil leader generated in the existing channel. Multi recoil leaders occur during the whole M process, which maintain M discharge. The main discharge form in return stroke stage is recoiling discharge. There are multi recoil leaders before return strokes, however, most of them cannot develop to ground, keep as an attempted leader until the last leader-stroke occurs. Adjacent two strokes with a short duration time of 4.5 ms have the same optical channel in optical images, but they are obviously different in development paths, which lead to a very short RS interval.

Keywords

• triggered lightning
• whole discharge process
• continuous interferometer
• multi-stroke