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| Titel |
Statistical characteristics of low-latitude ionospheric field-aligned irregularities obtained with the Piura VHF radar |
| VerfasserIn |
J. L. Chau, R. F. Woodman, L. A. Flores |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 20, no. 8 ; Nr. 20, no. 8, S.1203-1212 |
| Datensatznummer |
250014444
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| Publikation (Nr.) |
 copernicus.org/angeo-20-1203-2002.pdf |
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| Zusammenfassung |
We present a summary of
the statistical characteristics of echoes from ionospheric (E- and F-region)
field-aligned irregularities obtained with the Piura VHF radar. This radar is
located at ~ 7.0° dip latitude, just outside the equatorial electrojet (EEJ)
region. Our results are based on (1) intermittent observations made between
1991 and 1999 just few days a year, and (2) continuous observations made
between January 2000 and June 2001. During most of the intermittent
observations, simultaneous measurements of EEJ and equatorial spread F (ESF)
irregularities were performed with the Jicamarca VHF radar. From the continuous
measurements, we have obtained the diurnal and seasonal characteristics of a
variety of parameters (percentage of occurrence, signal-to-noise ratio and/or
Doppler velocities) from the lower and upper E-region irregularities and also
from F-region irregularities over Piura. For example, we have found that (1)
the E-region echoes are stronger and occur more frequently during local summer
(i.e. between December and March); (2) between May and June, the E-region
echoes are weaker and occur less frequently; moreover, during these months, a
semidiurnal wave with large amplitudes is observed in the meridional wind (>
100 ms- 1); (3) there is vertical wavelength of about 20 km in the
Doppler velocity, particularly after midnight; (4) the lower (upper) E-region
Doppler velocities are influenced mainly by meridional winds (equatorial
F-region vertical drifts). In addition, we have observed that the seasonal and
daily occurrences of Piura F-region irregularities are similar to the
occurrence of topside ESF irregularities over Jicamarca. The likelihood of
occurrence of F-region irregularities over Piura and, therefore, topside ESF
over Jicamarca is greater when there are no E-region irregularities over Piura.
On the other hand, there is more probability of observing bottomtype/bottomside
ESF irregularities over Jicamarca when E-region irregularities are observed
over Piura.
Key words. Ionosphere (ionospheric
irregularities; equatorial ionosphere; instruments and techniques) |
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