@Article{EliasBarbShibSouz:2014:EfSoCy,
               author = "Elias, Ana G. and Barbas, Blas F. de Haro and Shibasaki, Kiyoto 
                         and Souza, Jonas Rodrigues de",
          affiliation = "{Consejo Nacional de Investigaciones Cientificas y Tecnicas 
                         (CONICET)} and {Universidad Nacional de Tucum{\'a}n} and 
                         {National Astronomical Observatory of Japan} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)}",
                title = "Effect of solar cycle 23 in foF2 trend estimation",
              journal = "Earth, Planets and Space",
                 year = "2014",
               volume = "66",
                month = "Sep.",
             keywords = "Ionospheric trends, Solar cycle 23, EUV proxies.",
             abstract = "The effect of including solar cycle 23 in foF2 trend estimation is 
                         assessed using experimental values for Slough (51.5 degrees N, 
                         359.4 degrees E) and Kokobunji (35.7 degrees N, 139.5 degrees E), 
                         and values obtained from two models: (1) the Sheffield University 
                         Plasmasphere-Ionosphere model, SUPIM, and (2) the International 
                         Reference Ionosphere, IRI. The dominant influence on the F2 layer 
                         is solar extreme ultraviolet (EUV) radiation, evinced by the 
                         almost 90\% variance of its parameters explained by solar EUV 
                         proxies such as the solar activity indices Rz and F10.7. This 
                         makes necessary to filter out solar activity effects prior to 
                         long-term trend estimation. Solar cycle 23 seems to have had an 
                         EUV emission different from that deduced from traditional solar 
                         EUV proxies. During maximum and descending phase of the cycle, Rz 
                         and F10.7 seem to underestimate EUV solar radiation, while during 
                         minimum, they overestimate EUV levels. Including this solar cycle 
                         in trend estimations then, and using traditional filtering 
                         techniques, may induce some spurious results. In the present work, 
                         filtering is done in the usual way considering the residuals of 
                         the linear regression between foF2 and F10.7, for both 
                         experimental and modeled values. foF2 trends become less negative 
                         as we include years after 2000, since foF2 systematically exceeds 
                         the values predicted by a linear fit between foF2 and F10.7. 
                         Trends become more negative again when solar cycle 23 minimum is 
                         included, since for this period, foF2 is systematically lower than 
                         values predicted by the linear fit. foF2 trends assessed with 
                         modeled foF2 values are less strong than those obtained with 
                         experimental foF2 values and more stable as solar cycle 23 is 
                         included in the trend estimation. Modeled trends may be thought of 
                         as a `zero level' trend due to the assumptions made in the process 
                         of trend estimation considering also that we are not dealing with 
                         ideal conditions or infinite time series.",
                  doi = "10.1186/1880-5981-66-111",
                  url = "http://dx.doi.org/10.1186/1880-5981-66-111",
                 issn = "1343-8832",
                label = "isi 2014-11 EliasHaroShibSouz:2014:EfSoCy",
             language = "en",
           targetfile = "Elias_effect.pdf",
        urlaccessdate = "26 abr. 2024"
}