Simultaneous observations of equatorial F-region plasma depletions over Brazil during the Spread-F Experiment (SpreadFEx)

Pautet, Pierre-Dominique; Taylor, Michael J.; Chapagain, Narayan P.; Takahashi, H.; Medeiros, A. F.; Sabbas, F. T. São; Fritts, David C.

doi:10.5194/angeo-27-2371-2009

Cited by 14 publications

(24 citation statements)

References 51 publications

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“…These characteristics are typical of previous bubble measurements over Brazil (e.g. Taylor et al, 1997b;Pimenta et al, 2003;Arruda et al, 2006), and separate investigations comparing the scale-sizes of the mesospheric gravity waves and F-region depletions, and the longitudinal variability in the bubble characteristics are presented by Takahashi et al (2009);Pautet et al (2009).…”

Section: Coordinated Observationssupporting

confidence: 57%

“…For the SpreadFEx campaign three high-quality imaging systems were used to quantify the occurrence and properties of mesospheric gravity waves and F-region depletions over Brazil using coordinated observations of several mesospheric and thermospheric nightglow emissions (see Pautet et al, 2009;Vargas et al, 2009;Wrasse et al, 2009). In particular, all-sky (180 • field of view) image measurements provide two-dimensional information with high spatial and temporal resolutions over a large geographic area (e.g.…”

Section: Imaging Instrumentationmentioning

confidence: 99%

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Characteristics of mesospheric gravity waves near the magnetic equator, Brazil, during the SpreadFEx campaign

et al. 2009

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Abstract. As part of the SpreadFEx campaign, coordinated optical and radio measurements were made from Brazil to investigate the occurrence and properties of equatorial Spread F, and to characterize the regional mesospheric gravity wave field. All-sky image measurements were made from two sites: Brasilia and Cariri located ∼10 • S of the magnetic equator and separated by ∼1500 km. In particular, the observations from Brasilia provided key data in relatively close proximity to expected convective sources of the gravity waves. High-quality image measurements of the mesospheric OH emission and the thermospheric OI (630 nm) emission were made during two consecutive new moon periods (22 September to 9 November 2005) providing extensive data on the occurrence and properties of F-region depletions and regional measurements of the dominant gravity wave characteristics at each site.A total of 120 wave displays were observed, comprising 94 short-period events and 26 medium-scale gravity waves. The characteristics of the small-scale waves agreed well with previous gravity wave studies from Brazil and other sites. However, significant differences in the wave propagation headings indicate dissimilar source regions for the Brasilia and Cariri datasets. The observed medium-scale gravity wave events constitute an important new dataset to study their mesospheric properties at equatorial latitudes. These data exhibited similar propagation headings to the shortperiod events, suggesting they originated from the same source regions. Medium-scale waves are generally less susceptible to wind filtering effects and modeling studies utilizing these data have successfully identified localized regions

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Section: Coordinated Observationssupporting

confidence: 57%

Section: Imaging Instrumentationmentioning

confidence: 99%

Characteristics of mesospheric gravity waves near the magnetic equator, Brazil, during the SpreadFEx campaign

et al. 2009

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“…The climatology and characteristics of low-latitude F-region plasma drift have been extensively studied over the past few decades using ground-based radar observations, optical measurements, ionosonde, and satellite observations [1,2,3,4,5,6,7,8]. The previous studies have shown that the night-time zonal plasma drifts in geomagnetically quiet days were eastward while plasma drift during the geomagnetic disturbance days are westward.…”

Section: Introductionmentioning

confidence: 99%

Equatorial ionospheric plasma drifts velocities using radar observations

Chapagain

2016

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This study presents the experimental results of the equatorial ionospheric plasma drift zonal velocity obtained from Incoherent Scatter Radar (ISR) observations for 6 selective days in 2011 from Jicamarca, Peru. Our results indicate that the daytime drifts are westward with peak values mostly below ~50 m/s, while the night time drifts velocities are eastward, with a maximum value up to 120 m/s at around local midnight hours. The drift velocity decreases during post-midnight hours and starts to reverse westward in early morning hours. Our plasma drifts results are in good agreement with results from previous radar studies and other measurement techniques.

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“…This technique is the same as applied to analyzing wave motions in mesospheric image data [e.g., Taylor and Garcia , 1995; Garcia et al , 1997]. The method used to measure the zonal velocity of the plasma bubble is similar to that proposed by Pimenta et al [2001] and employed by Pautet et al [2009] and Chapagain et al [2011] to quantify bubble drift speeds over equatorial Brazil and Christmas Island, respectively. In each case, the velocities of individual bubbles were estimated using the embedded depletion structures visible from pairs of consecutive OI (630.0 nm) images separated in time by ∼12 min.…”

Section: Observations and Data Analysismentioning

confidence: 99%

Equatorial plasma bubble zonal velocity using 630.0 nm airglow observations and plasma drift modeling over Ascension Island

et al. 2012

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LST and is followed by eastward propagation with an average speed of $90-120 m/s prior to local midnight, rapidly decreasing around the midnight and postmidnight periods. The Ascension results are compared with similar observations from Christmas Island in order to examine the longitudinal variations of EPB development and propagation. The observed EPB velocities from Ascension Island are also compared with the results of a plasma drift model. In a case study during the night of 4-5 April, the velocity reveals unusual latitudinal shear, up to 0.12 m/s/km, with a reversal to westward flow at low latitudes while eastward flow is maintained at higher latitudes. Consequently, the bubble rotates counterclockwise and tilts eastward, significantly away from alignment with the geomagnetic field lines. The westward reversal of the drift motion near the geomagnetic equator is most likely the result of a reversal in the F region dynamo or from a large increase in the altitude of the shear node in the F region plasma drift at the geomagnetic equator.Citation: Chapagain, N. P., M. J. Taylor, J. J. Makela, and T. M. Duly (2012), Equatorial plasma bubble zonal velocity using 630.0 nm airglow observations and plasma drift modeling over Ascension Island,

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Simultaneous observations of equatorial F-region plasma depletions over Brazil during the Spread-F Experiment (SpreadFEx)

Cited by 14 publications

References 51 publications

Characteristics of mesospheric gravity waves near the magnetic equator, Brazil, during the SpreadFEx campaign

Characteristics of mesospheric gravity waves near the magnetic equator, Brazil, during the SpreadFEx campaign

Equatorial ionospheric plasma drifts velocities using radar observations

Equatorial plasma bubble zonal velocity using 630.0 nm airglow observations and plasma drift modeling over Ascension Island

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