Characteristics of attempted cloud-to-ground lightning leaders
Abstract
We investigate signatures of a rarely reported lightning phenomenon called isolated breakdown process or an attempted cloud-to-ground lightning leader using data records collected by the broadband magnetic-field receiver BLESKA (Broadband Lightning Electromagnetic Signal Keeper Analyzer - a ground based version of the IME-HF analyzer for the TARANIS spacecraft mission). The isolated breakdown process is characterized by pulse activity typical for preliminary breakdown process which does not lead to a regular return stroke. There are only a few previous studies reporting this not fully understood lightning process from Florida and Sweden. Our analysis is based on data recorded during two observational campaigns held in Corsica in autumn 2015 and 2018. Our results indicate that the isolated breakdown processes are quite common in the West Mediterranean basin.
We use a broadband magnetic loop antenna which detects signals in the frequency range of the BLESKA receiver from 5 kHz to 37 MHz with a sampling rate of 80 MHz. This data set is combined with the measurements of the network of 12 LMA (Lightning Mapping Array) stations SAETTA (Suivi de l'Activité Electrique Tridimensionnelle Totale de l'Atmosphère) which detect the VHF radiation emitted by cloud discharges in the 60-66 MHz band. We also use information about locations and peak currents of CG strokes and IC discharges detected by MÉTÉORAGE, the French VLF/LF lightning location system. Using the broadband magnetic-field measurements we estimate fine characteristics of more then two hundreds of isolated breakdown pulse sequences. We also analyze the time correlation of magnetic-field pulses measured by the broadband receiver with respect to VHF radiation recorded by SAETTA using both raw and reconstructed SAETTA data. Combining the BLESKA and SAETTA measurements we follow the development of each evolving discharge. We recognize two typical scenarios: the discharges continue to propagate horizontally for at least 150 ms or they die out within a few tens of milliseconds from the first breakdown pulse. By means of numerical modeling we verify that a potential barrier starts to appear inside the thundercloud for a strong lower positive charge center. This barrier can block further propagation of lightning leaders towards the ground.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMAE13B3213K
- Keywords:
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- 3304 Atmospheric electricity;
- ATMOSPHERIC PROCESSES;
- 3324 Lightning;
- ATMOSPHERIC PROCESSES;
- 3346 Planetary meteorology;
- ATMOSPHERIC PROCESSES;
- 3394 Instruments and techniques;
- ATMOSPHERIC PROCESSES