author = "Carmo, Carolina de Sousa do and Becker Guedes, F{\'a}bio and 
                         Camargo, P. O. and Monico, J. F. G.",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Universidade Estadual 
                         Paulista (UNESP)} and {Universidade Estadual Paulista (UNESP)}",
                title = "Comparison between different tec calculation techniques to 
                         characterize the ionosphere in the brazilian sector",
                 year = "2018",
         organization = "Latin American Conference on Space Geophysics, 11. (COLAGE)",
             abstract = "The Total Electron Content (TEC) of the ionosphere can be 
                         calculated by parameters observed by GPS receivers located in the 
                         ground. As a result of the differential phase and group 
                         calculation, the non-dispersive terms are canceled, leaving terms 
                         due to biases of the satellites and the receiver together with the 
                         ionospheric error contribution to the signal. The slant TEC (STEC) 
                         corresponds to an arc of TEC for each satellite measured by a 
                         given receiver. The combination of the various STECs observed by a 
                         receiver using selected methods and mapping functions results in a 
                         vertical TEC (VTEC) over the ground station. In this work, the 
                         performance of three different VTEC calculation techniques, each 
                         one using their own methods to eliminate biases and to obtain VTEC 
                         from STECs, is evaluated to describe the ionosphere conditions in 
                         the equatorial and low latitude regions in the Brazilian sector. I 
                         order to do this, data from a station in the equatorial region, 
                         Sao Luis, and a station in the southern crest of the Equatorial 
                         Ionization Anomaly (EIA), Cachoeira Paulista, were used. The study 
                         was made for a period of minimum solar activity (November 2008 to 
                         October 2009) and one of maximum solar activity (November 2014 to 
                         October 2015) and the seasonality of TEC along the year was also 
                         studied. The three techniques used are: (I) the technique 
                         developed by the University of Nagoya, Japan, and adjusted at the 
                         National Institute of Space Research (INPE), Brazil, to be used by 
                         the Brazilian Space Weather Program (EMBRACE), (II) a technique 
                         developed at Boston College, USA, and (III) the method proposed by 
                         the International Centre for Theoretical Physics (ICTP), Italy. 
                         The evaluation of the TEC curves obtained showed that all three 
                         techniques present results consistent with each other but with 
                         some small divergences in certain periods. The three techniques 
                         show the significant reduction of the TEC in the period of minimum 
                         solar activity and during the winter in any condition of solar 
                         activity. All techniques showed an increase in TEC at the station 
                         under the crest of the EIA in the summer and during the equinoxes 
                         due to the intensification of the fountain effect during the day 
                         and the pre-reversion peak at the sunset. The large discrepancies 
                         between the results obtained by the three techniques were observed 
                         during the beginning of the night hours due to the presence of 
                         ionospheric irregularities. The method used in INPE responds well 
                         to the daily, seasonal and solar cycle variations of the TEC, 
                         presenting, on several occasions, intermediate results with 
                         respect to the other techniques in the Brazilian region, showing 
                         to be suitable to be used by EMBRACE program to monitoring this 
  conference-location = "Buenos Aires, Argentina",
      conference-year = "16-20 abr.",
             language = "en",
        urlaccessdate = "18 jan. 2021"