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| Titel |
Decameter mid-latitude sporadic-E irregularities in relation with gravity waves |
| VerfasserIn |
A. Bourdillon, E. Lefur, C. Haldoupis, Y. Roux, J. Ménard, J. Delloue |
| 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 ; 15, no. 7 ; Nr. 15, no. 7, S.925-934 |
| Datensatznummer |
250012877
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| Publikation (Nr.) |
 copernicus.org/angeo-15-925-1997.pdf |
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| Zusammenfassung |
| HF radar observations of mid-latitude spo-
radic-E irregularities carried out with the Valensole
radar in South France are compared with simultaneous
ionosonde measurements underneath the irregularity
zones. In a previous study of Valensole radar data, it has
been shown that HF backscatter from the night-time
mid-latitude E region is usually associated with large-
scale wave-like modulations. To obtain more informa-
tion on the geophysical conditions prevailing during
backscatter events, a new experiment was performed
which also included a vertical ionosonde beneath the
scattering region. The data to be presented here are from
two periods when radar scattering appeared simulta-
neously with large variations in the virtual height and
the Doppler velocity of F-layer re¯ected echoes mea-
sured with the vertical ionosonde, indicating very clearly
the passage of atmospheric gravity waves (AGWs). The
e.ect of the atmospheric waves on the sporadic-E layer
is not always as marked as it is in the F region. In the
®rst event, the passage of the AGWs is accompanied by
an upward followed by a downward movement of the
Es-layer. The apparent descending movement of the
Es-layer from 135 to 110 km in less than 10 min
corresponded to a positive (downward) Doppler velocity
of 35 m/s measured by the vertical ionosonde, and was
accompanied by a range variation in the radar scattering
region with a negative rate of about 90±110 m/s. In the
second event, the Es-layer is not as strongly disturbed as
in the previous one, but, nevertheless, the range varia-
tions of the scattering region can still be associated with
height ¯uctuations of the Es-layer. |
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