Spontaneous Emergence of Space Stems Ahead of Negative Leaders in Lightning and Long Sparks

DOI: 
10.1029/2019GL082063
Publication date: 
26/04/2019
Main author: 
Malagón-Romero A.
IAA authors: 
Malagón-Romero, A.;Luque, A.
Authors: 
Malagón-Romero A., Luque A.
Journal: 
Geophysical Research Letters
Refereed: 
Yes
Publication type: 
Article
Pages: 
4029-4038
Abstract: 
We investigate the emergence of space stems ahead of negative leaders. These are luminous spots that appear ahead of an advancing leader mediating the leader's stepped propagation. We show that space stems start as regions of locally depleted conductivity that form in the streamers of the corona around the leader. An attachment instability enhances the electric field leading to strongly inhomogeneous, bright, and locally warmer regions ahead of the leader that explain the existing observations. Since the attachment instability is only triggered by fields above 10 kV/cm and internal electric fields are lower in positive than in negative streamers, our results explain why, although common in negative leaders, space stems, and stepping are hardly observed if not absent in positive leaders. Further work is required to fully explain the streamer to leader transition, which requires an electric current persisting for timescales longer than the typical attachment time of electrons, around 100 ns. ©2019. The Authors.
Database: 
SCOPUS
ADS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85064087925&doi=10.1029%2f2019GL082063&partnerID=40&md5=95429637e2e6c250b69d4bdfc51f759b
ADS Bibcode: 
2019GeoRL..46.4029M
Keywords: 
attachment instability; ionization wave; space stem; streamer; streamer to leader