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100
95
90
85
28Å
L
[NO]
80
UV
[
O
2
(
1
g
)
]
75
70
65
Cosmic rays
60
10
3
10
2
10
1
10
1
10
2
10
3
1
Ion pair production rate (cm
3
sec
1
)
Figure 1.9
Ionization rates in the quiet daytime D region for solar minimum conditions
and solar zenith angles near 60
◦
. [After Thomas (1974). Reproduced with permission of
the American Geophysical Union.]
Table 1.1
Important Ion Reactions in the D Region
Reaction Type
Name
Rate
xy
+
+
α
∗
D
=
10
−
7
cm
3
s
−
1
1
e
→
x
+
y
Dissociative recombination
4
×
2H(H
2
O)
n
+
e
→
H(H
2
O)
n
−
1
+
10
−
5
cm
3
s
−
1
H
2
O Cluster-ion recombination
α
d
=
5
×
xy
+
+
z
−
→
10
−
6
cm
3
s
−
1
3
xy
+
z
Ion-ion mutual neutralization
α
i
=
z
−
+
10
−
30
cm
6
s
−
1
+
+
→
α
=
4
z
z
e
z
Three-body attachment
z
−
+
4s
−
1
5
hv
→
z
+
e
Photo detachment
d
=
0
.
z
−
+
10
−
10
cm
3
s
−
1
6
m
→
mz
+
e
Associative detachment
f
=
The simplest version of a D region model (Banks and Kockarts, 1973), which
contains most of the chemistry, is thus
dn
+
dt
−
α
d
n
e
n
+
−
α
i
n
+
n
−
=
In
dn
−
dt
n
2
n
e
−
n
−
(
fn
m
+
α
i
n
+
)
=
α
d
+
dn
e
dt
=
−
α
d
n
e
n
+
−
α
n
2
n
e
+
n
−
(
In
d
+
fn
m
)
where
I
is the photoionization rate (mostly Lyman
on [NO]),
n
is the NO
density,
n
+
is the dominant positive ion density,
n
−
is the dominant negative ion
α
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