Geoscience Reference
In-Depth Information
The integration of Eq.
5.2
gives
J
.h/
D
J
0
exp
S
UV
./
h
0
N
0
exp
;
h
h
0
(5.3)
where J
0
is the source of the sun's radiation spectrum density.
Respectively, the source of the ionization is equal to
dJ
.h/
dh
‰
UV
D
:
(5.4)
After the substitution of Eq.
5.3
in Eq.
5.4
and differentiation, one gets
‰
UV
.h/
D
J
0
S
UV
./
N
0
exp
exp
S
UV
./
N
0
exp
:
h
h
0
h
h
0
(5.5)
An effective photo-ionization cross section can be represented as (Kramers
1923
)
77
!
O
2
80
!
N
2
; nm
S
UV
./
S
0
3
; <
m
D
S
0
D
10
24
; cm
2
ı
nm
3
:
(5.6)
A spectral density of UV radiation with wavelength shorter than 80 nm,
generated, basically, by the sun crown, is represented in Fig.
5.7
(Chertok
1994
).
It can be approximated by black body dependence with the appropriate tempera-
ture:
I
0
0
4
exp
0
„
2c
k
B
T
cor
D
100 nm
; cm
3
s
1
I
UV
./
D
0
D
1
(5.7)
T
cor
100 eV;
0
3
10
6
cm
2
s
1
nm
1
:
The value
I
0
corresponds to the average between a maximum and a minimum of
the sun's activity.
The source of ionization by UV radiation is determined by the integral:
Z
m
1
cm
3
s
: (5.8)
J
UV
.h/
D
I
UV
./S
UV
./N.h/ exp .
S
UV
./N.h/h
0
/ d;
0
