3D Lightning Imaging in Time: Detection Techniques

Forum APF
25 novembre 2014
Des éclairs en 3D résolus dans le temps
1
Des éclairs en 3D résolus dans le temps
Gérard BERGER
Directeur de Recherches honoraire du CNRS

The spectrum of lightning and some
applications to its detection (LLS)
Gérard Berger
1
, Vladimir Rakov
2
2
Gérard Berger
, Vladimir Rakov
1 ABB Pôle Foudre, Bagnères de Bigorre, France
2 University of Gainesville, Florida, USA
RADIO 2014, Mauritius

Cloud
-
to
-
Cloud discharges (67-75 %)
Types of Lightning Discharges
3
Types of lightning discharges from cumulonimbus
Cloud-to-ground (25-33%) Cloud-to-air
Intracloud
Cloud
-
to
-
cloud
3

EM radiation from Lightning
Like any conductor where a large variable current is
flowing, a lightning flash emits an electromagnetic
wave.
This
radiation
can
be
detected
at
large
distances
from
4
This
radiation
can
be
detected
at
large
distances
from
the flash, sometimes at thousands of kilometres,
even at world scale.

Lightning electromagnetic signatures
Every type of lightning discharge shows a typical
range of frequencies, from VLF to VHF, which for
instance allows to discriminate emission
properties
of
flashes
between
a
cloud
and
ground
5
properties
of
flashes
between
a
cloud
and
ground
(CG discharge) from flashes inside a cloud (IC
discharge). In particular, VHF signals emitted in
the cloud (generally non visible) characterize the
initiation of strong ionization between pockets of
charge separated according to their polarity.