Bibliography
Notice:
|
Found 12 entries in the Bibliography.
Showing entries from 1 through 12
2022 |
The influence of sudden stratospheric warming (SSW) on the ionosphere and ionospheric irregularities has been studied extensively over the years. However, majority of these Agyei-Yeboah, Ebenezer; Fagundes, Paulo; Tardelli, Alexandre; Pillat, Valdir; Vieira, Francisco; Arcanjo, Mateus; Published by: Advances in Space Research Published on: YEAR: 2022   DOI: 10.1016/j.asr.2022.08.065 |
2016 |
We studied the response of the ionosphere (F region) in the Brazilian sector during extreme space weather event of 17 March 2015 using a large network of 102 GPS- total electron content (TEC) stations. It is observed that the vertical total electron content (VTEC) was severely disturbed during the storm main and recovery phases. A wavelike oscillation with three peaks was observed in the TEC diurnal variation from equator to low latitudes during the storm main phase on 17\textendash18 March 2015. The latitudinal extent of the wavelike oscillation peaks decreased from the beginning of the main phase toward the recovery phase. The first peak extended from beyond 0\textdegreeS to 30\textdegreeS, the second occurred from 6\textdegreeS to 25\textdegreeS, whereas the third diurnal peaks was confined from 13\textdegreeS to 25\textdegreeS. In addition, a strong negative phase in VTEC variations was observed during the recovery phase on 18\textendash19 March 2015. This ionospheric negative phase was stronger at low latitudes than in the equatorial region. Also, two latitudinal chains of GPS-TEC stations from equatorial region to low latitudes in the east and west Brazilian sectors are used to investigate the storm time behavior of the equatorial ionization anomaly (EIA) in the east and west Brazilian sectors. We observed an anomalous behavior in EIA caused by the wavelike oscillations during the storm main phase on 17 March, and suppression of the EIA, resulting from the negative phase in VTEC, in the storm recovery phase. Fagundes, P.; Cardoso, F.; Fejer, B.; Venkatesh, K.; Ribeiro, B.; Pillat, V.; Published by: Journal of Geophysical Research: Space Physics Published on: 05/2016 YEAR: 2016   DOI: 10.1002/2015JA022214 |
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 |
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: |
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: |
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: |
Becker-Guedes, F; Sahai, Y; Fagundes, PR; Espinoza, ES; Pillat, VG; Lima, WLC; Basu, Su; Basu, Sa; Otsuka, Y; Shiokawa, K; MacKenzie, E.; Bittencourt, J.; Published by: Published on: |
2005 |
Sahai, Y; Fagundes, PR; Becker-Guedes, F; Bolzan, MJA; , Abalde; Pillat, VG; De Jesus, R; Lima, WLC; Crowley, G; Shiokawa, K; , others; Published by: Journal of Geophysical Research: Space Physics Published on: |
1