Geoscience Reference
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100
Cassino, Brazil
5 November 1966
x
5208
NO
1
Fe
1
O
1
Mg
1
90
H
1
.(H
2
O)
2
Total
80
H
3
O
1
H
1
.(H
2
O)
3
70
10
2
10
3
10
4
10
5
1
10
Ion concentration (cm
23
)
Figure 1.8
Positive-ion composition measurements at Cassino, Brazil, for full sun con-
ditions before a solar eclipse. [After Narcisi et al. (1972). Reproduced with permission of
Pergamon Press.]
frequencies. Thus, AM radio signals are highly absorbed during the day but are
almost unattenuated at night. FM radio and TV are much higher frequency and
almost entirely pass through the whole system into space. The ionization rates
of various high-energy photons and particles are plotted in Fig. 1.9. These rates
correspond to the
P
j
in (2.7). Table 1.1 provides some of the important reactions.
Ignoring transport, three continuity equations must be considered, all of the
form,
∂
n
j
∂
=
P
j
−
L
j
t
where
j
is electrons, negative ions, or positive ions. At the time these coupled
equations were first solved, reaction 2 in Table 1.1 was not well understood. But
to create the ledge visible in all the rocket profiles in Figs. 1.7a and 1.7b, Reid
(1970) needed the high effective rate of recombination plotted in Fig. 1.10. He
concluded that such a high rate required the existence of water cluster ions in
the 75-85 km height range, which were found later by Narcisi et al. (1972), as
illustrated in Figure 1.8. Notice that the rate for reaction 2 is nearly 100 times
that of reaction 1. A strong variation of
α
d
with altitude shown in Fig. 1.10 is
caused by the change in the cluster-ion composition. Below 75 km, reaction 3
becomes important. The incoherent scatter radar at Arecibo has been used in the
D region and verified most of the rocket results, albeit with less spatial resolution
(Ioannidis and Farley, 1974).
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