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6.4 Effects of Particle Precipitation at Midlatitudes
Shen et al. (1976) concluded that both the intense intermediate layers in Fig. 5.22
and the general enhancement of F-layer valley ionization were associated with
energetic particle precipitation. To test this idea, extensive studies involv-
ing a number of rocket flights at midlatitudes have been conducted by Voss
and Smith (1979, 1980a, b). Summary plots are reproduced in Fig. 6.11a-c.
Figure 6.11a shows plasma density profiles for four different values of the mag-
netic activity index
K
p
. The highest
K
p
profile shows F-layer valley densities an
order of magnitude higher than the lowest
K
p
profile. A layer with peak den-
sity at 135 km is also evident in the high-
K
p
profile. Figure 6.11b shows both
the particle flux and the ionization rate as functions of a specialized magnetic
200
190
180
3
4
2
1
170
160
Wallops Island
150
1 0003 EST
1 Nov 1972
D
ST
52173, K
p
5 8
140
2 2306 EST
18 Apr 1974
D
ST
52
130
59, K
p
5
5
1
120
3 2340 EST
29 Jun 1974
D
ST
52
11, K
p
5
3
1
110
4 0001 EST
10 Aug 1977
D
ST
52
100
43, K
p
5
3
1
90
80
70
60
50
1
10
2
10
3
10
4
10
5
10
Electron density (cm
23
)
Figure 6.11a
Nighttime electron density profiles from rockets launched at Wallops
Island. [After Voss and Smith (1979). Reproduced with permission of the American
Geophysical Union.]
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