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polarization electric fields, even when loaded by the F region. An example simu-
lation is shown in Fig. 6.40, with the integrated F-region conductivity (
PF
)is
set so that
H
are the integrated Pedersen
and Hall conductivities, respectively, of the
E
s
layer. This conductivity ratio is
critical for determining the activity level of the instability, and a detailed inves-
tigation of its morphology is needed in the future. Fig. 6.40 shows isodensity
contours for cross sections of the
E
s
layer at successive times on the left and the
H
=
2
.
5
(
PE
+
PF
)
, where
PE
and
4
2
0
2
4
10
0
t
0 min
t
0 min
10
15
10
5
0
5
10
15
15
10
5
0
5
10
15
4
2
0
2
4
10
0
t
4.5 min
t
4.5 min
10
1
5
10
5
0
5
10
1
5
15
10
5
0
5
10
1
5
4
10
2
0
2
4
0
t
7.4 min
t
7.4 min
10
1
5
10
5
0
5
10
1
5
15
10
5
0
5
10
1
5
4
10
2
0
2
4
0
t
10.4 min
t
10.4 min
10
1
5
10
5
0
5
10
1
5
15
10
5
0
5
10
1
5
4
10
2
0
2
4
0
t
14.7 min
t
14.7 min
10
15
10
5
0
5
10
15
15
10
5
0
5
10
1
5
10
t
19.8 min
0
t
19.8 min
10
15
10
5
0
5
10
15
1
40
80
120
160
200
Figure 6.40
The left panels show isodensity contours on cross sections through the
E
s
L,
from numerical simulations, for six successive times. At time
t
=
0 the layer is perturbed
by a
4 km sinusoidal altitude modulation, and the subsequent panels show the growth
phase of the
E
s
layer instability. (The cross-sectional plane is rotated about the horizontal
southwest-northeast line—(the horizontal axis)—so it contains the magnetic field.) The
right-hand panels show the corresponding electric fields at the original layer altitude of
105 km, plotted versus position on the horizontal axis. All scales are kilometers, except
for the electric field ordinate, which is mV/m. The integrated Pedersen conductivities of
the
E
s
and F layers (
±
1
/
PF
) and the integrated Hall conductivity of the
E
s
layer
(
H
) satisfy
H
=
2
.
5
(
PE
+
PF
)
. The line color indicates the percentage of initial peak
density. See Color Plate 23.
PE
and
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