Optical observations of plasma bubble westward drifts over Brazilian tropical region

Paulino, Igo; Medeiros, A. F.; Buriti, R. A.; Sobral, J. H. A.; Takahashi, H.; Gobbi, D.

doi:10.1016/j.jastp.2010.01.015

Cited by 20 publications

(19 citation statements)

References 36 publications

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“…2, and as suggested earlier, observations could have been made under disturbed dynamo conditions (Blanc and Richmond 1980;Fejer et al 2017). Westward motion of the ionospheric irregularities are known to occur during disturbed dynamo (Abdu et al 2003;Paulino et al 2010), and therefore, our observations confirm the occurrence of low-latitude disturbances.…”

Section: Event 3: August 3-4 2016supporting

confidence: 89%

Multi-instrumented observations of the equatorial F-region during June solstice: large-scale wave structures and spread-F

Rodrigues

Hickey

Zhan

et al. 2018

Prog Earth Planet Sci

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Typical equatorial spread-F events are often said to occur during post-sunset, equinox conditions in most longitude sectors. Recent studies, however, have found an unexpected high occurrence of ionospheric F-region irregularities during June solstice, when conditions are believed to be unfavorable for the development of plasma instabilities responsible for equatorial spread-F (ESF). This study reports new results of a multi-instrumented investigation with the objective to better specify the occurrence of these atypical June solstice ESF in the American sector and better understand the conditions prior to their development. We present the first observations of June solstice ESF events over the Jicamarca Radio Observatory (11.95°S, 76.87°W, ∼ 1 • dip latitude) made by a 14-panel version of the Advanced Modular Incoherent Scatter Radar system (AMISR-14). The observations were made between July 11 and August 4, 2016, under low solar flux conditions and in conjunction with dual-frequency GPS, airglow, and digisonde measurements. We found echoes occurring in the pre-, post-, and both pre-and post-midnight sectors. While at least some of these June solstice ESF events could have been attributed to disturbed electric fields, a few events also occurred during geomagnetically quiet conditions. The late appearance (22:00 LT or later) of three of the observed events, during clear-sky nights, provided a unique opportunity to investigate the equatorial bottomside F-region conditions, prior to ESF, using nighttime airglow measurements. We found that the airglow measurements (630 nm) made by a collocated all-sky camera show the occurrence of ionospheric bottomside F-region perturbations prior to the detection of ESF echoes in all three nights. The airglow fluctuations appear as early as 1 hour prior to radar echoes, grow in amplitude, and then coincide with ESF structures observed by AMISR-14 and GPS TEC measurements. They also show some of the features of the so-called large-scale wave structures (LSWS) that have been detected, previously, using other types of observations and have been suggested to be precursors of ESF. The bottomside fluctuations have zonal spacings between 300 and 500 km, are aligned with the magnetic meridian, and extend at least a few degrees in magnetic latitude.

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Section: Event 3: August 3-4 2016supporting

confidence: 89%

Multi-instrumented observations of the equatorial F-region during June solstice: large-scale wave structures and spread-F

Rodrigues

Hickey

Zhan

et al. 2018

Prog Earth Planet Sci

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“…This is the first report of such a distinct pattern of spread F for the Brazilian equatorial region, though it was observed earlier at the low-latitude station CP (Brazil) for the solar minimum 2008-2009 by Candido et al (2011). By distinct we mean that it occurs in postmidnight hours propagating westward, which is not usually observed during solar minimum unless there is a previous eastward EPB structure propagation, as mentioned by Paulino et al (2010). A careful analysis of equatorial ionograms and other plots from digisonde soundings suggests modifications in the ionospheric plasma density structuring, such as those associated with plasma density depletions, which are responsible for a variety of spread-F-layer patterns.…”

Section: Discussionmentioning

confidence: 54%

“…The depletions also propagated over CZ (350 km south of FZ) with mean westward velocities ∼ 60 m s −1 , which are similar to the propagation velocities of the irregularities observed with the digisonde at FZ. Some authors have demonstrated that EPBs can also present westward propagation after midnight during quiet times (Paulino et al, 2010;Sobral et al, 2011). However, those studies reported that the depletions associated with EPBs should first present movement to the east earlier in the evening and reversal westward at later hours.…”

Section: Depletions In the Airglow Oi 6300 Nm Imagesmentioning

confidence: 98%

Postmidnight equatorial plasma irregularities on the June solstice during low solar activity – a case study

et al. 2019

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Abstract. We present a case study of unusual spread-F structures observed by ionosondes at two equatorial and low-latitude Brazilian stations – São Luís (SL: 44.2∘ W, 2.33∘ S; dip angle: −6.9∘) and Fortaleza (FZ: 38.45∘ W, 3.9∘ S; dip angle: −16∘). The irregularity structures observed from midnight to postmidnight hours of moderate solar activity (F10.7 < 97 sfu, where 1 sfu = 10−22 W m−2 s−1) have characteristics different from typical post-sunset equatorial spread F. The spread-F traces first appeared at or above the F-layer peak and gradually became well-formed mixed spread F. They also appeared as plasma depletions in the 630.0 nm airglow emissions made by a wide-angle imager located at the nearby low-latitude station Cajazeiras (CZ: 38.56∘ W, 6.87∘ S; dip angle: −21.4∘). The irregularities appeared first over FZ and later over SL, giving evidence of an unusual westward propagation or a horizontal plasma advection. The drift-mode operation available in one of the ionosondes (a digital portable sounder, DPS-4) has enabled us to analyze the horizontal drift velocities and directions of the irregularity movement. We also analyzed the neutral wind velocity measured by a Fabry–Pérot interferometer (FPI) installed at CZ and discuss its possible role in the development of the irregularities.

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“…It has been designed to keep track of the spatial and temporal variations of OH, OI5577, 6300 nm airglow emissions (e.g. Paulino et al, 2010).…”

Section: The All Sky Imagermentioning

confidence: 99%

Investigation of sources of gravity waves observed in the Brazilian Equatorial region on 08 April 2005

Dare-Idowu¹,

Paulino²,

Figueiredo³

et al. 2019

Preprint

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On 08 April 2005, a strong gravity wave activity (more than 3 hours) was observed in São João do Cariri (7.4 o S, 36.5 o W).These waves propagated to the southeast and presented different spectral characteristics (wavelength, period and phase speed). Using OH airglow images, the parameters of 5 observed gravity waves were calculated; the wavelengths ranged from 90 to 150 km, the periods from ~26 to 67 min and the phase speeds ranged between 32 to 71 m/s. A reserve ray-tracing 15 analysis was performed to research the possible sources of these detected waves. The ray-tracing database was composed of temperature profiles from NRLMSISE-00 model and SABER measurements and wind profiles from HWM model and meteor radar data. According to the ray path, the likely source of these observed gravity waves was the Inter Tropical Convergence Zone with intense convective processes taking place in the northern part of the observatory. Also, the observed preferential propagation direction of the waves to the southeast could be explained using blocking diagrams, i.e. due to the wind filtering 20 process.

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Optical observations of plasma bubble westward drifts over Brazilian tropical region

Cited by 20 publications

References 36 publications

Multi-instrumented observations of the equatorial F-region during June solstice: large-scale wave structures and spread-F

Multi-instrumented observations of the equatorial F-region during June solstice: large-scale wave structures and spread-F

Postmidnight equatorial plasma irregularities on the June solstice during low solar activity – a case study

Investigation of sources of gravity waves observed in the Brazilian Equatorial region on 08 April 2005

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