A comparison of TEC fluctuations and scintillations at Ascension Island

Basu, Susanto; Groves, K. M.; Quinn, John M.; Doherty, Patricia H.

doi:10.1016/s1364-6826(99)00052-8

Cited by 245 publications

(198 citation statements)

References 12 publications

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“…Basu et al, 1999). These instabilities develop in the early evening hours, during the pre-reversal enhancement of the zonal electric field, when strong upward plasma drifts cause the F-region ionosphere to rise significantly (Heelis et al, 1974;Fejer et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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

et al. 2009

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“…More recently, ESF has been shown to create significant errors in GPS position measurements at low-latitudes when the line-of-sight satellite signals pass through strong equatorial plasma bubbles (EPB) also termed depletions (e.g., Basu et al, 1999;Kelley et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2009

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Abstract. From September to November 2005, the NASA Living with a Star program supported the Spread-F Experiment campaign (SpreadFEx) in Brazil to study the effects of convectively generated gravity waves on the ionosphere and their role in seeding Rayleigh-Taylor instabilities, and associated equatorial plasma bubbles. Several US and Brazilian institutes deployed a broad range of instruments (all-sky imagers, digisondes, photometers, meteor/VHF radars, GPS receivers) covering a large area of Brazil. The campaign was divided in two observational phases centered on the September and October new moon periods. During these periods, an Utah State University (USU) all-sky CCD imager operated at São João d'Aliança (14.8 • S, 47.6 • W), near Brasilia, and a Brazilian all-sky CCD imager located at Cariri (7.4 • S, 36 • W), observed simultaneously the evolution of the ionospheric bubbles in the OI (630 nm) emission and the mesospheric gravity wave field. The two sites had approximately the same magnetic latitude (9-10 • S) but were separated in longitude by ∼1500 km.Plasma bubbles were observed on every clear night (17 from Brasilia and 19 from Cariri, with 8 coincident nights). These joint datasets provided important information for characterizing the ionospheric depletions during the campaign and to perform a novel longitudinal investigation of their variability. Measurements of the drift velocities at both sites are in good agreement with previous studies, however, the overlapping fields of view revealed significant differences in the occurrence and structure of the plasma bubbles, providing new evidence for localized generation. This paper summarizes the observed bubble characteristics important for reCorrespondence to: P.-D. Pautet (dominiquepautet@gmail.com) lated investigations of their seeding mechanisms associated with gravity wave activity.

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“…ROTI measurements can be used to predict the presence of ionospheric scintillation also (Basu et al, 1999 …”

Section: Resultsmentioning

confidence: 99%

Investigation of ionospheric gradients for GAGAN application

2009

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To cater to the needs of aviation applications, GPS Aided GEO Augmented Navigation (GAGAN) system is being implemented over the Indian region. The most prominent parameter affecting the navigation accuracy of GAGAN is ionospheric delay which is a function of TEC. In the equatorial and low latitude regions such as India, TEC is often quite high with large spatial gradients. Carrier phase data from the GAGAN network of Indian TEC Stations is used for estimating ionospheric gradients in multiple viewing directions. Rate of TEC (ROT) and Rate of TEC Index (ROTI) are calculated to identify the ionospheric gradients. Among the satellite signals arriving in multiple directions, the signals which suffer from severe ionospheric gradients are identified and avoided for improving GAGAN positional accuracy. The outcome of this paper will be helpful for improving GAGAN system performance.

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A comparison of TEC fluctuations and scintillations at Ascension Island

Cited by 245 publications

References 12 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

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

Investigation of ionospheric gradients for GAGAN application

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