Dancing Sprites Above a Lightning Mapping Array - an analysis of the
storm and flash/sprite developments
Abstract
We present a multi-instrumental analysis of a 20-hour duration Mesoscale
Convective System (MCS) over the northwestern Mediterranean sea on
September 21, 2019, that produced 21 sprites recorded with a video
camera, of which 19 (90$\%$) were dancing sprites. The
asymmetric trailing stratiform MCS developed in strong convective
conditions (3500 J kg$^{-1}$) and formed a large and persistent
overshoot with several convective cores (up to 25,000 km$^2$ with
cloud top temperature $<$
-66$^{\circ}$C). It exhibited a bow echo structure
with a probable inverted charge dipole within the convective region
before the main sprite production period and associated with a large
decrease of the negative cloud-to-ground (CG) flash rate. The sprite
producing positive cloud-to-ground (SP+CG) flashes mainly initiated at
the edge of the convective line on the side of the stratiform region.
The flashes propagated over long distances (up to
$\sim$ 200 km) across it producing both positive and
negative CG strokes. Some parent flashes initiated within the stratiform
region close to convective structures and propagated reversely. The 19
dancing sprite events included 49 sequences, of which 46
(94$\%$) were associated with distinct SP+CG strokes
and 3 with surges during the continuing current. An especially bright
and wide sprite sequence was produced by three distinct SP+CG strokes
that occurred within 3 ms and separated by 54 km. This sprite sequence
could be classified as a new sprite category resembling to a
â\euroœwallâ\euro? but structured in three groups, each associated
with one of the +CG strokes, but not separated by the video imagery.