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Bidirectional leader development in sprite‐producing positive cloud‐to‐ground flashes: Origins and characteristics of positive and negative leaders
Author(s) -
Velde Oscar A.,
Montanyà Joan,
Soula Serge,
Pineda Nicolau,
Mlynarczyk Janusz
Publication year - 2014
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2013jd021291
Subject(s) - sprite (computer graphics) , physics , meteorology , stroke (engine) , telecommunications , computer science , computer vision , thermodynamics
Thirty‐five sprite‐producing lightning flashes were recorded in nine nights in different seasons at the east coast of Spain with a 3D Lightning Mapping Array (LMA) since July 2011. A low‐frequency time‐of‐arrival network provided data on emissions from return strokes and intracloud processes and a very‐high‐frequency interferometer network produced complementary lightning data. This study analyzes the bidirectional development of flashes in order to understand the positioning and timing of the positive cloud‐to‐ground stroke (+CG) and its consequences for charge neutralization by negative leaders, affecting sprite morphology. A summary of negative leader extents, altitudes, and speeds before and after the + CG stroke is provided, as well as positive leader origins and inferred speeds. Negative leader speeds exhibited modes at 10 5 and 5 × 10 5 m s −1 . Five examples with different evolutions are discussed: (1) Slow bidirectional development with negative leader termination before the + CG stroke; (2) Fast bidirectional development with the negative leader continuing after the + CG stroke. (3) Slow‐fast bidirectional development with a negative leader exhibiting a sudden lowering and speed increase; (4) Fast secondary bidirectional development from an in‐cloud horizontal positive leader. Negative leaders propagated rapidly into the upper positive charge layer, continuing after the + CG stroke; (5) Slow bidirectional development with a long negative leader (50 km) subject to cutoff while the original positive leader remained trapped inside negative charge. A + CG stroke subsequently occurred under the old negative leader channel. Carrot sprites tended to be associated with fast extending leaders after the stroke, columniform/mixed sprites with slower side branches.