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Found 12 entries in the Bibliography.
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2021 |
Effects of the 12 May 2021 Geomagnetic Storm on Georeferencing Precision In this work, we present the positioning error analysis of the 12 May 2021 moderate geomagnetic storm. The storm happened during spring in the northern hemisphere (fall in the south). We selected 868 GNSS stations around the globe to study the ionospheric and the apparent position variations. We compared the day of the storm with the three previous days. The analysis shows the global impact of the storm. In the quiet days, 93\% of the stations had 3D errors less than 10 cm, while during the storm, only 41\% kept this level of accuracy. The higher impact was over the Up component. Although the stations have algorithms to correct ionospheric disturbances, the inaccuracies lasted for nine hours. The most severe effects on the positioning errors were noticed in the South American sector. More than 60\% of the perturbed stations were located in this region. We also studied the effects produced by two other similar geomagnetic storms that occurred on 27 March 2017 and on 5 August 2019. The comparison of the storms shows that the effects on position inaccuracies are not directly deductible neither from the characteristics of geomagnetic storms nor from enhancement and/or variations of the ionospheric plasma. Valdés-Abreu, Juan; Díaz, Marcos; Báez, Juan; Stable-Sánchez, Yohadne; Published by: Remote Sensing Published on: jan YEAR: 2021   DOI: 10.3390/rs14010038 Geomagnetic storms; total electron content; global navigation satellite system; Global positioning system; precise point positioning; rate of change of the tec index |
2012 |
The main objective of the present investigation has been to compare the ionospheric parameters (NmF2 and hmF2) observed by two ground-based ionospheric sounders (one at PALMAS- located near the magnetic equator and the other at Sao Jose dos Campos-located in the low-latitude region) in the Brazilian sector with that by the satellite FORMOSAT-3/COSMIC radio occultation (RO) measurements during two geomagnetic storms which occurred in December 2006 and July 2009. It should be pointed out that in spite of increasing the latitude (to 10\textdegree) and longitude (to 20\textdegree) around the stations; we had very few common observations. It has been observed that both the peak electron density (NmF2) and peak height (hmF2) observed by two different techniques (space-borne COSMIC and ground-based ionosondes) during both the geomagnetic storm events compares fairly well (with high correlation coefficients) at the two stations in the Brazilian sector. It should be pointed out that due to equatorial spread F (ESF) in the first storm (December 2006) and no-reflections from the ionosphere during nighttime in the second storm (July 2009), we had virtually daytime data from the two ionosondes. Sahai, Y.; de Jesus, R.; Fagundes, P.R.; Selhorst, C.L.; de Abreu, A.J.; Ram, Tulasi; Aragon-Angel, A.; Pillat, V.G.; Abalde, J.R.; Lima, W.L.C.; Bittencourt, J.A.; Published by: Advances in Space Research Published on: 11/2012 YEAR: 2012   DOI: 10.1016/j.asr.2012.07.006 COSMIC satellite; F-region; geomagnetic storm; Ionosphere; Low solar activity |
This paper presents a study of thermospheric and ionospheric response to the 2008 minor sudden stratospheric warming (SSW) event. This period was characterized by low solar and geomagnetic activity. The study was performed using the Global Self-consistent Model of Thermosphere, Ionosphere, and Protonosphere (GSM TIP). Model results were compared with ionosonde data from Irkutsk, Kaliningrad, Sao Jose dos Campos, and Jicamarca. The SSW event was modeled by specifying the temperature and density perturbations at the lower boundary of the GSM TIP (80 km altitude). GSM TIP simulation allowed the reproduction of the lower thermosphere temperature disturbances (the occurrence of the quasi-wave 1 structure at 80\textendash130 km altitude with a vertical scale of \~40 km), the negative response of F2 region electron density and the positive response of electron temperature at 300 km during the 2008 minor SSW event. The main formation mechanism of the global ionospheric response is due to the disturbances (decrease) in then(O)/n(N2) ratio. The change in zonal electric field is another important mechanism of the ionospheric response at low latitudes. Korenkov, Y.; Klimenko, V.; Klimenko, M.; Bessarab, F.; Korenkova, N.; Ratovsky, K.; Chernigovskaya, M.; Shcherbakov, A.; Sahai, Y.; Fagundes, P.; de Jesus, R.; de Abreu, A.; Condor, P.; Published by: Journal of Geophysical Research Published on: 10/2012 YEAR: 2012   DOI: 10.1029/2012JA018018 Electric field; Ionosphere; sudden stratospheric warming; thermosphere |
2011 |
Sahai, Y.; Fagundes, P.; de Jesus, R.; de Abreu, A.; Crowley, G.; Kikuchi, T.; Huang, C.-S.; Pillat, V.; Guarnieri, F.; Abalde, J.; Bittencourt, J.; Published by: Annales Geophysicae Published on: Jan-01-2011 YEAR: 2011   DOI: 10.5194/angeo-29-919-2011 |
Sahai, Y; De Abreu, AJ; Fagundes, PR; De Jesus, R; Crowley, G; Klimenko, MV; Klimenko, VV; Brunini, C; Gende, M; Pillat, VG; , others; Published by: Asian Journal of Physics Published on: |
This study presents the Global Self-Consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) numerical simulations of the 9–14 September 2005 geomagnetic Klimenko, MV; Klimenko, VV; Ratovsky, KG; Goncharenko, LP; Sahai, Y; Fagundes, PR; De Jesus, R; De Abreu, AJ; Vesnin, AM; Published by: Radio Science Published on: |
2010 |
Sahai, Yogeshwar; de Jesus, Rodolfo; Fagundes, Paulo; de Abreu, Alessandro; Crowley, Geoff; Pillat, Valdir; Guede, Jose; Bittencourt, Jose; Published by: 38th COSPAR Scientific Assembly Published on: |
2009 |
Sahai, Y; Fagundes, PR; De Jesus, R; De Abreu, AJ; Crowley, G; Pillat, VG; Guarnieri, FL; , Abalde; Bittencourt, JA; Published by: Published on: |
Sahai, Y; Becker-Guedes, F; Fagundes, PR; De Jesus, R; De Abreu, AJ; Paxton, LJ; Goncharenko, LP; Brunini, C; Gende, M; Ferreira, AS; , others; Published by: Journal of Geophysical Research: Space Physics Published on: |
2008 |
Sahai, Y.; Becker-Guedes, F.; Fagundes, P.R.; Lima, W.L.C.; de Abreu, A.J.; Guarnieri, F.L.; Candido, C.M.N.; Pillat, V.G.; Published by: Published on: |
2007 |
Brazilian ionosphere behavior during an intense solar flare The 28 October 2003 solar flare was one of the most intense solar flares observed in the recent past. In the present investigation we show the ionospheric effects observed in the Becker-Guedes, F; Sahai, Y; Fagundes, PR; Abreu, A; Pillat, VG; Lima, WLC; Published by: Published on: YEAR: 2007   DOI: https://doi.org/10.3997/2214-4609-pdb.172.SBGF0393_07 |
Sahai, Y; Becker-Guedes, F; Fagundes, PR; Lima, WLC; De Abreu, AJ; Guarnieri, FL; Candido, CMN; Pillat, VG; Published by: Published on: |
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