author = "Sahai, Yogeshwar and Bittencourt, Jos{\'e} Augusto and Sobral, 
                         Jos{\'e} Humberto Andrade and Fagundes, Paulo Roberto and 
                         Takahashi, Hisao",
                title = "Observations of ionospheric plasma depletions using OI 630.0 nm 
                         nightglow imaging",
              journal = "Revista Brasileira de Geof{\'{\i}}sica",
                 year = "1996",
               volume = "14",
               number = "1",
                pages = "15--28",
             keywords = "AERONOMIA, ionosf{\'e}ricos, bolhas de plasma, luminescencia, 
                         deple{\c{c}}{\~a}o, emiss{\~a}o, imagens, ionospherics, olasma 
                         bubbles, airglow, depletion, emission5images.",
             abstract = "Ionospheric plasma irregularities associated with nighttime 
                         equatorial spread-F phenomena have been tile subject of intensive 
                         experimental and theoretical investigations during recent years. 
                         Large scale plasma deplections, referred to as transequatorial 
                         bubbles or plumes, continue to attract considerable attention. The 
                         studies of ionosphere plasma irregularities assume great 
                         importance, because the irregularities degrade the radio wave 
                         signals passing through the region and, therefore, have 
                         considerable influence on the ionospheric/trans-ionospheric radio 
                         wave communications. The F-region nightglow emissions arising from 
                         ionospheric recombination processes can be used to remotely 
                         observe the dynamics of transequatorial ionospheric plasma bubbles 
                         and smaller scale plasma irregularities. In a collaborative 
                         project between the Center for Space Physics, Boston University, 
                         USA, and the National Institute for Space Research (INPE), Brazil, 
                         an all-sky imaging system was put in operation at Cachoeira 
                         Paulista (22.7S, 45.0 W, dip latitude 15.8 S), in March 1987. 
                         This wide angle imaging technique provides an unique capability of 
                         permitting observations over regions covering several million 
                         square kilometers from a single observing station. Also, regular 
                         measurements of several nightglow emissions and ionospheric 
                         sounding are carried out at Cachoeira Paulista and Fortaleza (3.9 
                         S, 38.4 W, dip latitude 3.7 S). A VH:IF electronic polarimeter 
                         was in operation at Cachoeira Paulista. This clustering of 
                         observational facilities in the Brazilian sector provided 
                         coincident and complementary observations of various upper 
                         atmospheric paramcte7-s. In this paper we present and discuss some 
                         features of the OI 630.0 nm emission all-sky imaging observations 
                         carried out during the period 1987-1999. The transequatorial 
                         ionospheric plasma bubbles manifest in all-sky optical imaging 
                         observations as nearly north-south aligned intensity-depleted 
                         regions. The observed seasonal variation of the airglow depletions 
                         shows a maximum during the summer months and virtually no airglow 
                         depletions during tile winter months. The case studies presented 
                         show different forms of generation and development phases of 
                         airglow depletions during the course of a night. The all-sky 
                         images also permitted the determination of tile altitude-latitude 
                         extent of the plasma depleted regions and some results are 
                         presented. It has been observed that the altitudes reached by the 
                         plasma depleted flux tubes over the magnetic equator in the 
                         Brazilian sector often exceed 2500 km.",
                 issn = "0102-261X",
                label = "9665",
           targetfile = "8746.pdf",
        urlaccessdate = "18 jan. 2021"