Geoscience Reference
In-Depth Information
33.027 (Upleg) Punta Lobos, Peru
March 12, 1983
10:34:36 L.T.
125.0
120.0
Non-geophysical
fluctuations
Two-stream
waves
115.0
110.0
105.0
.217 dB
100.0
Gradient drift
waves
(
mV/m)
2
Hz
95.0
90.0
,2
55 dB
85.0
10
3
Electron density (cm
23
)
10
4
10
5
0
500
1000
Frequency (Hz)
Figure 4.28
Frequency-height sonogram of the horizontal component of the irregulari-
ties measured during the upleg of rocket 33.027 during strong electrojet conditions. This
instrument had a low-frequency roll-off (3 dB) at 16Hz. The electron density profile (left)
shows the presence of large-scale irregularities. Both panels show nongeophysical “inter-
ference” above about 110 km. [After Pfaff et al. (1987a). Reproduced with permission of
the American Geophysical Union.]
for electric field fluctuations is plotted on the right side. The data divide clearly
into three segments. Above the peak in electron density the profile is smooth,
and the wave data extend to high frequencies. Below 102 km and in the region
of upward electron density gradients, the plasma density is structured, and the
wave data come in strong bursts that do not extend to very high frequencies.
Between these regions, an upward gradient exists and the fluctuations are both
patchy and extend to high frequencies. The total east-west electric field has been
measured as a function of time and altitude during this flight and is shown in
the upper panel of Fig. 4.29. The data show very intense alternating electric
fields organized in large-scale features very reminiscent of the radar data shown
in Fig. 4.25. In fact, large-scale waves of this type were detected by the radar
between 103 and 106 km and were a primary launch criterion for the rocket
flight. It is of interest to note that as the rocket altitude increased from 92 to
106 km, the signal changed qualitatively from a turbulent sinusoid to a squared-
off and seemingly saturated waveform. Similar features were detected during
the downleg. In the lower half of Fig. 4.29, a short time interval is blown up
to better show the steep edges and saturation-like waveforms. Note that within
these waveforms the vertical
perturbation
electron drift velocity,
B
2
,
exceeds the sound speed. The electron density fluctuation data in this height
range display similar, but not identical, waveforms with peak
δ
E
×
B
/
δ
n
/
n
values in
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