Comparison of GPS-TEC measurements with IRI2012-TEC predictions in the Brazilian sector during the unusual solar minimum 2009

DE ABREU, A. J.; MARTIN, I. M.; DE JESUS, R.; BOLZAN, M. J. A.; VENKATESH, K.; FAGUNDES, P. R.; ALVAREZ M.; GENDE, M.; KUMAR, S.

ANNALS OF GEOPHYSICS

EDITRICE COMPOSITORI BOLOGNA

Lugar: Bologna; Año: 2017 vol. 60

1593-5213

The total electron content (TEC) derived from two Global PositioningSystem (GPS) receivers localized at Palmas (PAL, 10.2oS, 48.2oW,dip latitude 5.5oS), near equatorial region, and São José dos Campos(SJC, 23.2oS, 45.9oW, dip latitude 17.6oS), under the southern crest ofthe equatorial ionization anomaly (EIA), in the Brazilian sector areused in this paper. TEC from the latest available IRI-2012 model at thesame locations is also used. A comparative study between GPS-TECand the IRI-2012 model is analyzed during the deep low solar activityperiod of 2009 in the unusual solar cycle 23. The measurements andthe modeled data show that the IRI-TEC model gives the better estima-tes of the GPS-TEC during the nighttime from January to Decembermonths at PAL and SJC. The IRI-TEC model shows larger differencesfrom the GPS-TEC in the afternoon hours, mainly at SJC. These di-screpancies observed at SJC in the afternoon hours for all months arepossibly due to the dynamics of EIA in consequence of the equatorialfountain effect. At PAL and SJC, oscillations of GPS-TEC with pe-riods around 16 days in April and periods around 27-32 days betweenSeptember and December possibly are noticed which could be relatedto a modulation of the semidiurnal tide and Sun?s rotation, respecti-vely. Also, oscillations with periods around 2-4 and 5-10 days fromJanuary to December are observed at PAL and SJC, possibly associatedwith the propagation of planetary waves.