Geoscience Reference
In-Depth Information
October 10-11, 1980
Arecibo, P.R.
550
450
100
350
0
150
October 11, 1980
Arecibo, P.R.
100
0
0
15
7.5
ˆ
V
gravity
5g·B/n
in
V
II
(measured)
0.0
2
150
20
00
04
08
02
04
Time (LT)
06
Time (LT)
(a)
(b)
Figure 5.17
(a) Height of the peak electron density (
h
max
)
, meridional plasma drift
velocity components (
V
⊥
N
and
V
||
), and peak in electron density (
n
max
)
measured over
Arecibo. (b) Calculated diffusion velocity and observed ion motion for the event illus-
trated in (a). [After Behnke et al. (1985). Reproduced with permission of the American
Geophysical Union.]
large eastward perturbation in
E
seen at Arecibo was also detected at Jicamarca
and was a clear magnetospheric effect (see the earlier discussion in Chapter 3).
Unfortunately, no neutral wind data were taken on this night. The anticorrelation
between
V
and slow change of
h
max
were occurring as usual until
about 0300, when the tropical and low-latitude ionospheric dynamo was inter-
rupted by the auroral event. The F-layer height increased dramatically due to
the large eastward electric field, which was only partially compensated by the
anticorrelation effect. To test this, the large observed downward
V
N
and
V
⊥
||
has been
superimposed on a calculated value of
g
/ν
in
sin
I
in Fig. 5.17b. The two curves
match very well, illustrating the tendency of gravity to counter extreme vertical
electrodynamic forcing. The peak height of the F layer surged upward when the
applied field existed (trying to reach equilibrium) and then began to fall when
the penetration electric field decreased.
Although complex, these two days at least can be more or less explained in a
straightforward manner. To avoid leaving the reader with the impression that
this is always the case, we discuss an event recorded on June 15-16, 1980.
Data from this night are presented in Fig. 5.18a and b in the same format as
Fig. 5.16a and b. Comparison of Fig. 5.18a and b shows that the field-aligned
||
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