@Article{NishinoMaYuRoScAb:2002:UnIoAb,
               author = "Nishino, M and Makita, K. and Yumoto, K. and Rodrigues, F. S. and 
                         Schuch, Nelson Jorge and Abdu, Mangalathayil Ali",
                title = "Unusual ionospheric absorption characterizing eneregetic electron 
                         precipitatio into the South Atlantic Magnetic Anomaly",
              journal = "Revista Eletr{\^o}nica da Faculdade de Farm{\'a}cia",
                 year = "2002",
               volume = "54",
               number = "9",
                pages = "907--916",
             keywords = "GEOF{\'{\I}}SICA ESPACIAL, precipita{\c{c}}{\~a}o de 
                         part{\'{\i}}culas, atividade geomagn{\'e}tica, tempestade, 
                         Particle precipitation, geomagnetic activity, storm.",
             abstract = "An imaging riometer (IRIS)was installed newly in the southern area 
                         of Brazil in order to investigate precipitation of energetic 
                         electrons into the South Atlantic Magnetic Anomaly (SAMA). An 
                         unusual ionospheric absorption event was observed in the nighttime 
                         (similar to20 h LT)near the maximum depression (D-st similar to 
                         -164 nT)and the following positive excursion during the strong 
                         geomagnetic storm on September 22-23, 1999. The unusual absorption 
                         that has short time-duration of 30-40 min shows two characteristic 
                         features: One feature is a sheet structure of the absorption 
                         appearing at the high-latitude part of the IRIS field-of-view, 
                         showing an eastward drift from the western to the eastern parts 
                         and subsequent retreat to the western part. Another feature is a 
                         meridionally elongated structure with a narrow longitudinal width 
                         (100-150 km)appearing from the zenith to the low-latitude part of 
                         the IRIS field-of-view, enhanced simultaneously with the sheet 
                         absorption, and is subsequently changed to a localized structure. 
                         These features likely characterize precipitation of energetic 
                         electrons into the SAMA ionosphere, associated with substorm 
                         occurrences during the strong geomagnetic storm. From the eastward 
                         drift (similar to250 m/s)of the sheet absorption, precipitating 
                         electrons are estimated to be similar to20 keV energies, assuming 
                         plasmaspheric electric fields of 1.8 mV/m. However, no ionospheric 
                         effect due to the precipitating electrons was definitely detected 
                         by the ionosonde measurements at Cachoeira Paulista, separated 
                         eastward by about 1000 km from the IRIS station.",
           copyholder = "SID/SCD",
                 issn = "1808-0804",
             language = "en",
           targetfile = "nishino.pdf",
        urlaccessdate = "16 jun. 2024"
}