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Open AccessArticle

Mean Zonal Drift Velocities of Plasma Bubbles Estimated from Keograms of Nightglow All-Sky Images from the Brazilian Sector

1
Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
2
Arecibo Observatory, University of Central Florida, Arecibo, FL 32816, USA
3
National Institute for Space Research, Sao Jose dos Campos 12227, Brazil
*
Author to whom correspondence should be addressed.
Atmosphere 2020, 11(1), 69; https://doi.org/10.3390/atmos11010069
Received: 21 November 2019 / Revised: 30 December 2019 / Accepted: 31 December 2019 / Published: 5 January 2020
We present in this work a method for estimation of equatorial plasma bubble (EPB) mean zonal drift velocities using keograms generated from images of the OI 6300.0 nm nightglow emission collected from an equatorial station–Cariri (7.4° S, 36.5° W), and a mid-latitude station–Cachoeira Paulista (22.7° S, 45° W), both in the Brazilian sector. The mean zonal drift velocities were estimated for 239 events recorded from 2000 to 2003 in Cariri, and for 56 events recorded over Cachoeira Paulista from 1998 to 2000. It was found that EPB zonal drift velocities are smaller (≈60 ms−1) for events occurring later in the night compared to those occurring earlier (≈150 ms−1). The decreasing rate of the zonal drift velocity is ≈10 ms−1/h. We have also found that, in general, bubble events appearing first in the west-most region of the keograms are faster than those appearing first in the east-most region. Larger zonal drift velocities occur from 19 to 23 LT in a longitude range from −37° to −33°, which shows that the keogram method can be used to describe vertical gradients in the thermospheric wind, assuming that the EPBs drift eastward with the zonal wind. The method of velocity estimation using keograms compares favorably against the mosaic method developed by Arruda, D.C.S, 2005, but the standard deviation of the residuals for the zonal drift velocities from the two methods is not small (≈15 ms−1). View Full-Text
Keywords: all-sky imager; ionospheric plasma bubble; zonal drift velocity; keograms; nightglow; OI6300 thermospheric emission all-sky imager; ionospheric plasma bubble; zonal drift velocity; keograms; nightglow; OI6300 thermospheric emission
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Vargas, F.; Brum, C.; Terra, P.; Gobbi, D. Mean Zonal Drift Velocities of Plasma Bubbles Estimated from Keograms of Nightglow All-Sky Images from the Brazilian Sector. Atmosphere 2020, 11, 69.

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