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| Titel |
Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread F |
| VerfasserIn |
F. S. Rodrigues, D. L. Hysell, E. R. Paula |
| 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 ; 26, no. 11 ; Nr. 26, no. 11 (2008-10-21), S.3355-3364 |
| Datensatznummer |
250016276
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| Publikation (Nr.) |
 copernicus.org/angeo-26-3355-2008.pdf |
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| Zusammenfassung |
| The 30 MHz coherent backscatter radar located at the equatorial observatory
in São Luís, Brazil (2.59° S, 44.21° W, −2.35° dip
lat) has been upgraded to perform coherent backscatter radar imaging. The
wide field-of-view of this radar makes it well suited for radar imaging
studies of ionospheric irregularities. Radar imaging observations were made
in support to the spread F Experiment (SpreadFEx) campaign. This paper
describes the system and imaging technique and presents results from a
bottom-type layer that preceded fully-developed radar plumes on 25 October
2005. The radar imaging technique was able to resolve decakilometric
structures within the bottom-type layer. These structures indicate the
presence of large-scale waves (~35 km) in the bottomside F-region with
phases that are alternately stable and unstable to wind-driven gradient drift
instabilities. The observations suggest that these waves can also cause the
initial perturbation necessary to initiate the Generalized Rayleigh-Taylor
instability leading to spread F. The electrodynamic conditions and the
scale length of the bottom-type layer structures suggest that the waves were
generated by the collisional shear instability. These results indicate that
monitoring bottom-type layers may provide helpful diagnostics for spread F
forecasting. |
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