Geoscience Reference
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The GUVI instrument aboard the TIMED satellite
Comparison of satellite (red)
and ground (gray) observations
of an equatorial plasma bubble
Equatorial plasma bubble
Equatorial arcs
Figure 6.15b GUVI observations of the 135.6-nm emission on September 22, 2002,
along with simultaneous ground-based observations. [After Kelley et al. (2003b). Repro-
duced with permission of the American Geophysical Union.] See Color Plate 15.
density gradient and vice versa. The depletions should thus structure on one side
or the other, depending on the zonal neutral wind direction.
Since the equatorial anomaly region is one of very high electron density—the
highest average electron density anywhere in the earth's ionosphere—the effect
of such structuring on transionospheric propagation is very pronounced. The
scintillation technique discussed in Appendix A has been used extensively in
the anomaly region to characterize the structure there and to better understand
the scintillation process itself. Even at a transmission frequency of 6GHz, up
to 6 dB of scintillation-induced amplitude variation has been detected in this
region. An example of data from the anomaly is shown in Fig. 6.16a and b.
In Fig. 6.16a, a schematic diagram shows the relative motion of an airplane
conducting scintillation measurements using satellite transmission through an
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