author = "Santana, Daniela Cristina and Sobral, Jos{\'e} Humberto Andrade 
                         and Takahashi, Hisao and Taylor, Michael J.",
                title = "Optical studies of the ionospheric irregularities over the 
                         Brazilian region by nocturnal images of the OI 630 nm emission",
              journal = "Advances in Space Research",
                 year = "2001",
               volume = "27",
               number = "6-7",
                pages = "1207--1212",
             keywords = "AERONOMIA, Brasil, bolhas de plasma, ionosf{\'e}ricas, 
                         irregularidades, aeroluminesc{\^e}ncia, imagnes, plasma bubbles, 
                         ionospherics, irregularities, airglow, images.",
             abstract = "This study is an extension of previous statistical studies (Sobral 
                         et al., 1990,1991,1999)of both the local time and latitude 
                         variations of the zonal drift velocities of ionospheric plasma 
                         depletions, over the Brazilian low latitude station Cachoeira 
                         Paulista - CP (22.54 degreesS, 45.00 degreesW). The past studies 
                         were based on OI 630 nm scanning photometer data and the present 
                         one is based on digital OI 630 nm airglow images obtained by an 
                         all-sky imager system. These data were gathered between October 
                         1998 and October 1999, at CP. The present results show that, in 
                         general, the velocities clearly tended to decrease with local 
                         time. Such a decrease should be associated with decreasing 
                         intensity of the vertical component of the ambient electric field 
                         which, in turn can be accounted for by recombination. All zonal 
                         drifts obtained for the 18 nights were eastwards. During equinox, 
                         the velocities clearly tended to decrease with local time at lower 
                         rates as compared with spring and summer. The highest and lowest 
                         zonal drift velocities, from all three seasons considered here, 
                         were observed to be in the summer similar to 180 ms(-1)at 21:45 
                         LT, and in the spring similar to 25 ms(-1)at 03:15 LT, 
                         respectively. Ionospheric plasma bubbles were detected out to the 
                         maximum extra-tropical geographical latitude of similar to 28 
                         degreesS, which was the highest latitude position analyzed in this 
                 issn = "0273-1177",
                label = "9755",
             language = "en",
           targetfile = "1-s2.0-S0273117701001995-main.pdf",
        urlaccessdate = "18 jan. 2021"