Geoscience Reference
In-Depth Information
Fig. 5.15
Distribution of the field of the cloud before lightning discharge (
continuous line
), the
field of the cloud without taking into account the conductivity of air (
dashed line
), and the critical
field (
dotted line
)
h
0
C
L
c
.
z
C
h
0
/
2
!
(5.19)
h
0
C
L
c
.
z
h
0
/
2
E
cloud
.
z
/
E
0
C
L
c
C
L
c
Let the cloud field increase by exponential law:
1
exp
;
t
ch
E
0
(5.20)
where
ch
is a characteristic time of charging in conducting media. It causes
occurrence of a polarization field:
tot
q
exp
ch
0
1
t
exp.
tot
t/
tot
q
1
E
polarization
D
E
cloud
.
z
/
@
A
;
1
(5.21)
where
q
is defined by Eq.
5.15
The resulting field of the cloud before lightning discharge is defined by the sum
E
before
D
E
cloud
C
E
polarization
:
(5.22)
The field in the atmosphere before lightning discharge, depending on altitude, is
shown in Fig.
5.15
(
r
D
0,
E
0
D
500 V/cm,
cloud
D
3,000 s).
