@Article{Kane:2009:EvDsAu,
               author = "Kane, Rajaram Purushottam",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)}",
                title = "Evolution of Dst and auroral indices during some severe 
                         geomagnetic storms",
              journal = "Revista Brasileira de Geof{\'{\i}}sica",
                 year = "2009",
               volume = "27",
               number = "2",
                pages = "151--163",
             keywords = "Dst geomagn{\'e}tico, {\'{\i}}ndices aurorais, tempestades 
                         geomagn{\'e}ticas, geomagnetic Dst, auroral indices, geomagnetic 
                         disturbances.",
             abstract = "As evolu{\c{c}}{\~o}es dos {\'{\i}}ndices Dst 
                         geomagn{\'e}tico e AU, AL e AE da aurora foram investigadas em 
                         rela{\c{c}}{\~a}o aos par{\^a}metros interplanet{\'a}rios de 
                         treze tempestades (com {\'{\i}}ndices Dst maiores que 250 nT), 
                         no per{\'{\i}}odo entre 1980 e 2003. As mudan{\c{c}}as no 
                         {\'{\i}}ndice Dst ocorreram toda vez que a componente Bz do 
                         campo B magn{\'e}tico interplanet{\'a}rio se tornou negativa. 
                         Entre os {\'{\i}}ndices da aurora, as mudan{\c{c}}as do 
                         {\'{\i}}ndice AU (representando o eletrojato da aurora em 
                         dire{\c{c}}{\~a}o ao leste) geralmente foram bem menores do que 
                         as do AL (representando o eletrojato da aurora para oeste). Ambos 
                         iniciaram um incremento quase que simultaneamente com o aumento do 
                         campo B magn{\'e}tico interplanet{\'a}rio, muito embora n{\~a}o 
                         tendo, {\`a}s vezes, a componente Bz se tornado negativa. 
                         Portanto, as mudan{\c{c}}as observadas em AU e AL podem preceder 
                         as da Dst por algumas horas e com isso t{\^e}m o potencial de 
                         previs{\~a}o de mudan{\c{c}}a. As mudan{\c{c}}as em AU e AL 
                         n{\~a}o se comportaram em paralelo e as suas 
                         inter-correla{\c{c}}{\~o}es foram quase nulas. Quando Bz se 
                         tornava negativa, invariavelmente AL era alto, por{\'e}m o 
                         reverso n{\~a}o se realizava. Grandes mudan{\c{c}}as em AL 
                         poderiam ocorrer mesmo quando Bz n{\~a}o fosse negativa (ou mesmo 
                         positiva). Valores de AL apresentaram muitos picos durante as 
                         tempestades e invariavelmente estes n{\~a}o se relacionaram 
                         {\`a}s mudan{\c{c}}as de Bz. Picos sucessivos de AL mostraram 
                         separa{\c{c}}{\~o}es em largas faixas, entre 40 e 160 minutos. 
                         An{\'a}lise espectral de valores hor{\'a}rios mostraram 
                         freq{\"u}entes periodicidades ao redor de 2-4 horas, 6 horas e 
                         8-9 horas. ABSTRACT: The evolutions of the geomagnetic Dst and 
                         auroral indices AU, AL, AE were examined in relation to 
                         interplanetary parameters for thirteen severe storms (Dst change 
                         exceeding 250 nT) during 1980-2003. Dst changes occurred every 
                         time Bz component of interplanetary magnetic field B turned 
                         negative. Among the auroral indices, changes in AU (representing 
                         an eastward auroral electrojet) were generally much smaller than 
                         changes in AL (representing a westward auroral electrojet), and 
                         both started increasing almost simultaneously with increases of 
                         interplanetary magnetic field B, even though its Bz component may 
                         not have turned negative. Hence AU and AL changes may precede Dst 
                         changes by a few hours and could have a prediction potential. AU 
                         and AL changes were not correlated well with each other; their 
                         inter-correlation was almost zero. Whenever Bz was negative, AL 
                         indices were invariably high, but the reverse was not true. Large 
                         AL changes could occur even when Bz was not negative (or even when 
                         positive). AL values showed many peaks during the storm and these 
                         were not invariably related to Bz changes. Successive AL peaks had 
                         separations in a wide range of 40-160 minutes. Spectral analysis 
                         of hourly values showed frequent periodicities around 2-4 hours, 6 
                         hours, and 8-9 hours.",
                  doi = "10.1590/S0102-261X2009000200001",
                  url = "http://dx.doi.org/10.1590/S0102-261X2009000200001",
                 issn = "0102-261X",
             language = "en",
           targetfile = "a01v27n2.pdf",
                  url = "http://dx.doi.org/10.1590/S0102-261X2009000200001",
        urlaccessdate = "15 jun. 2024"
}