@InProceedings{SilvaAlvePadi:2017:ExAmCh,
               author = "Silva, Graziela Belmira Dias da and Alves, Livia Ribeiro and 
                         Padilha, Ant{\^o}nio Lopes",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)}",
                title = "Experimental amplitude characterization of Pc3 and Pc5 pulsations 
                         at the brazilian equatorial region",
            booktitle = "Proceedings...",
                 year = "2017",
         organization = "AGU Fall Meeting",
             abstract = "Daytime equatorial electrojet currents (EEJ) are known to amplify 
                         geomagnetic variations on the ground in the equatorial region, 
                         with the possible exception of Pc3 pulsations for which there are 
                         reports of both amplification and damping in the pulsation 
                         amplitude near the magnetic equator. To clarify the EEJ effects on 
                         ground continuous pulsations (Pc) in the Brazilian equatorial 
                         region, we statistically analyzed the amplitude structure of Pc3 
                         (10 45 s) and Pc5 (150 600 s) pulsations recorded preferably 
                         during quiet days at multiple equatorial to low latitude stations 
                         (L = 1.00 1.12) nearly aligned along the 10° magnetic meridian. It 
                         was observed that diurnal Pc5s were amplified at all stations of 
                         the equatorial region, but mainly at those closest to the dip 
                         equator (latitudes less than 2°), whereas diurnal Pc3s were 
                         preferentially damped at equatorial stations, especially at one 
                         station under the dip equator. We interpret these differences as 
                         associated with different mechanisms of pulsation generation and 
                         transmission, and to the increase of Cowling conductivity in the 
                         diurnal equatorial ionosphere. Daytime Pc5s are transmitted 
                         horizontally in the TM0 mode from polar latitudes and amplified in 
                         the equatorial region by the higher ionospheric conductivity. On 
                         the other hand, daytime Pc3s are preferably upstream waves 
                         generated by ion-cyclotron instability on the bow shock, which 
                         propagate as compressional waves along the equatorial plane of the 
                         magnetosphere and are damped by the high conductivity of the 
                         equatorial ionosphere before reaching the ground. Our data also 
                         show significant sunrise terminator effects in Pc3 pulsations at 
                         the stations closest to the dip equator. However, on contrary to 
                         reported at other longitudes, in the Brazilian equatorial region 
                         the sunrise effect increases the H-to-D (north-south to east-west) 
                         amplitude ratio. We suggest that these significant differences 
                         could be arising from the markedly different magnetic declination 
                         angles between the Brazilian sector and the regions of the other 
                         studies. In our case, the H-component amplification can be 
                         explained by enhancements of the zonal (eastward) electric field 
                         near the magnetic equator driven by F region neutral winds (the F 
                         region dynamo) shortly after sunrise.",
  conference-location = "New Orleans",
      conference-year = "11-15 Dec.",
             language = "en",
           targetfile = "silva_experimental.pdf",
        urlaccessdate = "28 abr. 2024"
}