Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I>
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 rada...
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doaj-112251533c5443c98891eab6e72bac3e2020-11-24T23:30:03ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762008-10-01263355336410.5194/angeo-26-3355-2008Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I>F. S. Rodrigues0F. S. Rodrigues1D. L. Hysell2E. R. de Paula3Cornell University, Earth and Atmospheric Sciences, 2122 Snee Hall, Ithaca, NY, 14853, USAnow at: ASTRA, 12703 Spectrum Drive 101, San Antonio, TX, 78249, USACornell University, Earth and Atmospheric Sciences, 2122 Snee Hall, Ithaca, NY, 14853, USAInstituto Nacional de Pesquisas Espaciais (INPE), P.O. Box 515, São José dos Campos, SP, BrazilThe 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 <I>F</I> 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 <I>F</I>. 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 <I>F</I> forecasting.https://www.ann-geophys.net/26/3355/2008/angeo-26-3355-2008.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
F. S. Rodrigues F. S. Rodrigues D. L. Hysell E. R. de Paula |
spellingShingle |
F. S. Rodrigues F. S. Rodrigues D. L. Hysell E. R. de Paula Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I> Annales Geophysicae |
author_facet |
F. S. Rodrigues F. S. Rodrigues D. L. Hysell E. R. de Paula |
author_sort |
F. S. Rodrigues |
title |
Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I> |
title_short |
Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I> |
title_full |
Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I> |
title_fullStr |
Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I> |
title_full_unstemmed |
Coherent backscatter radar imaging in Brazil: large-scale waves in the bottomside F-region at the onset of equatorial spread <I>F</I> |
title_sort |
coherent backscatter radar imaging in brazil: large-scale waves in the bottomside f-region at the onset of equatorial spread <i>f</i> |
publisher |
Copernicus Publications |
series |
Annales Geophysicae |
issn |
0992-7689 1432-0576 |
publishDate |
2008-10-01 |
description |
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 <I>F</I> 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 <I>F</I>. 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 <I>F</I>
forecasting. |
url |
https://www.ann-geophys.net/26/3355/2008/angeo-26-3355-2008.pdf |
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