@Article{SelhorstCasVálCosShi:2011:Be17GH,
               author = "Selhorst, Caius Lucius and Castro, Guillermo Gim{\'e}nez and 
                         V{\'a}lio, Adriana and Costa, Joaquim Eduardo Rezende and 
                         Shibasaki, K.",
          affiliation = "Universidade do Vale do Para{\'{\i}}ba-UNIVAP, S{\~a}o 
                         Jos{\'e} dos Campos, SP, Brazilcaius@univap.br), AB(CRAAM, 
                         Universidade Presbiteriana Mackenzie, S{\~a}o Paulo, SP, Brazil) 
                         and Universidade do Vale do Para{\'{\i}}ba-UNIVAP, S{\~a}o 
                         Jos{\'e} dos Campos, SP, Brazilcaius@univap.br), AB(CRAAM, 
                         Universidade Presbiteriana Mackenzie, S{\~a}o Paulo, SP, Brazil) 
                         and Universidade do Vale do Para{\'{\i}}ba-UNIVAP, S{\~a}o 
                         Jos{\'e} dos Campos, SP, Brazilcaius@univap.br), AB(CRAAM, 
                         Universidade Presbiteriana Mackenzie, S{\~a}o Paulo, SP, Brazil) 
                         and {Instituto Nacional de Pesquisas Espaciais (INPE)} and NoRH, 
                         Nobeyama Radioheliograph, Japan",
                title = "The Behavior of the 17 GHz Solar Radius and Limb Brightening in 
                         the Spotless Minimum XXIII/XXIV",
              journal = "Astrophysical Journal",
                 year = "2011",
               volume = "734",
               number = "1",
                month = "June",
             keywords = "Sun: activity, Sun: faculae, plages, Sun: general, Sun: radio 
                         radiation.",
             abstract = "he current solar minimum has surprised the entire solar community 
                         because the spotless period is presently almost 2-3 years longer 
                         than the usual minima. To better understand this, we studied the 
                         variation of the solar radius and the polar limb brightening at 17 
                         GHz, comparing the results from the minimum at the end of cycle 
                         XXIII with those of the previous one. Daily maps obtained by the 
                         Nobeyama Radioheliograph (NoRH) from 1992 through 2010 were 
                         analyzed. Whereas the variation of the solar radius at radio 
                         frequencies indicates the heating of the solar atmosphere due to 
                         solar activity, the limb brightening intensity depends on the 
                         organization of the polar magnetic field of the Sun, including the 
                         global dipole and the features formed around it. These features 
                         are more prominent during minima periods. As a common result, 
                         researchers have observed a decrease in both radius and limb 
                         brightness intensity at 17 GHz during the present minimum when 
                         compared with the previous one. The mean solar radius is 0farcs9 ± 
                         0farcs6 smaller and the limb brightening reduced its intensity by 
                         around 20%. Both decrements are interpreted in terms of the weaker 
                         solar chromospheric activity of the present cycle. Measurement of 
                         the radius and limb brightening at 17 GHz can be used as an 
                         alternative solar activity index and should be included in the set 
                         of parameters used to predict future cycles.",
                  doi = "10.1088/0004-637X/734/1/64",
                  url = "http://dx.doi.org/10.1088/0004-637X/734/1/64",
                 issn = "0004-637X and 1538-4357",
             language = "en",
        urlaccessdate = "11 maio 2024"
}