@Article{FrancoHajrEcheBolz:2021:StSoAc,
               author = "Franco, Adriane Marques de Souza and Hajra, Rajkumar and Echer, 
                         Ezequiel and Bolzan, Maur{\'{\i}}cio Jos{\'e} Alves",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Indian 
                         Institute of Technology Indore} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)} and {Universidade Federal de Jatai}",
                title = "Seasonal features of geomagnetic activity: a study on the solar 
                         activity dependence",
              journal = "Annales Geophysicae",
                 year = "2021",
               volume = "39",
               number = "5",
                pages = "929--943",
                month = "Oct.",
             abstract = "Seasonal features of geomagnetic activity and their 
                         solar-wind-interplanetary drivers are studied using more than five 
                         solar cycles of geomagnetic activity and solar wind observations. 
                         This study involves a total of 1296 geomagnetic storms of varying 
                         intensity identified using the Dst index from January 1963 to 
                         December 2019, a total of 75 863 substorms identified from the 
                         SuperMAG AL/SML index from January 1976 to December 2019 and a 
                         total of 145 high-intensity long-duration continuous auroral 
                         electrojet (AE) activity (HILDCAA) events identified using the AE 
                         index from January 1975 to December 2017. The occurrence rates of 
                         the substorms and geomagnetic storms, including moderate (-50nT >= 
                         Dst >-100nT) and intense (-100nT >= Dst >-250nT) storms, exhibit a 
                         significant semi-annual variation (periodicity similar to 6 
                         months), while the super storms (Dst <= -250 nT) and HILDCAAs do 
                         not exhibit any clear seasonal feature. The geomagnetic activity 
                         indices Dst and ap exhibit a semi-annual variation, while AE 
                         exhibits an annual variation (periodicity similar to 1 year). The 
                         annual and semi-annual variations are attributed to the annual 
                         variation of the solar wind speed Vsw and the semi-annual 
                         variation of the coupling function VBs (where V = V-sw, and B-s is 
                         the southward component of the interplanetary magnetic field), 
                         respectively. We present a detailed analysis of the annual and 
                         semi-annual variations and their dependencies on the solar 
                         activity cycles separated as the odd, even, weak and strong solar 
                         cycles.",
                  doi = "10.5194/angeo-39-929-2021",
                  url = "http://dx.doi.org/10.5194/angeo-39-929-2021",
                 issn = "0992-7689",
             language = "en",
           targetfile = "franco_seasonal.pdf",
        urlaccessdate = "20 maio 2024"
}