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10
2
5
cm
2
3
N
0
3
10
2
5
cm
2
3
N
0
3
0.0
0.5
1.0
1.5
2.0
2.5
0.0
0.5
1.0
1.5
2.0
2.5
534
534
300 sec
700 sec
1.5E5
1.5E5
463
463
1.5E5
1.5E5
1.0E5
1.0E4
1.0E3
1.0E2
1.0E1
1.0E0
393
393
1.0E5
1.0E4
1.0E3
1.0E2
1.0E1
1.0E0
322
322
252
252
2
100
2
50
0
50
100
2
100
2
50
0
(km)
50
100
(km)
10
2
5
cm
2
3
10
2
5
cm
2
3
N
0
N
0
3
3
0.0
0.5
1.0
1.5
2.0
2.5
0.0
0.5
1.0
1.5
2.0
2.5
534
534
1200 sec
1000 sec
1.5E5
1.5E5
463
463
1.5E5
1.0E5
1.0E4
1.0E3
1.0E2
1.0E1
1.0E0
393
393
1.5E5
1.0ES
1.0E4
1.0E3
1.0E2
1.0E1
1 0E0
322
322
252
252
2
100
2
50
0
(km)
50
100
100
50
0
(km)
50
100
2
2
Figure 4.16b
Contour plots showing computer simulations of the Rayleigh-Taylor insta-
bility for a 100 km scale perturbation, initially of 5%magnitude. Contours are labeled in
units of reciprocal cubic centimeters. [After Zalesak and Ossakow (1980). Reproduced
with permission of the American Geophysical Union.]
tilted plume drifting eastward across the field of view. The result is a C-shaped
structure, as recorded in Figs. 4.1 and 4.2. The scanning radar data plotted in
Fig. 4.14 have reversedC-shapes, since the scans are orientedwith east to the right
and west to the left—the opposite of 4.16c. The data and simulations are thus
in excellent agreement. The eastward zonal plasma flow is due to the F-region
dynamo, which must be powerful enough to drive the off-equatorial E-region
loads. A likely explanation is that the depleted region polarizes and drifts more
slowly eastward than the background plasma. For example, consider the region
near the top of the plume. The vertical current is given by
σ
p
(
uB
+
E
z
)
, which is
upward because
uB
for an F-region dynamo. Recall that
E
is negative—
that is, the vertical electric field is downward. But inside the plume
>
|
E
z
|
σ
p
is smaller
than outside, and thus to maintain the current across the boundary,
|
E
z
|
must
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