Properties of Electromagnetic Signals Generated During the Development of Natural Lightning Discharges
Abstract
Analysis of electromagnetic signals emitted by natural lightning discharges is a way to investigate all evolution stages of lightning flashes. We present a study of the initiation stage for selected cloud-to-ground lightning flashes from the data collected in the Mediterranean during autumn 2015.
We compared measurements of the broadband receiver BLESKA to the sources of narrowband very high frequency (VHF) radiation detected by the Lightning Mapping Array SAETTA. We verified the findings of Kolmašová et al. (2018) on a larger dataset: strong VHF signals detected by individual lightning mapping array (LMA) stations during the first 1-3 ms of the flash duration corresponded in time to the intense peaks of preliminary breakdown pulses.
Such correlation indicates a fast step-like extension of lightning channels that leads to the emission of electromagnetic radiation in a wide range of frequencies. Using the 3D located VHF sources, we roughly estimated the altitude of lightning initiation and discussed it with respect to the locations of the charge regions in the thundercloud.
We thus demonstrated the importance of using a combination of data from different measurements for 3D mapping of the development of the lightning channel inside the thundercloud.