author = "Abdu, Mangalathyil Ali and Medeiros, Rui Tertuliano and 
                         Bittencourt, Jos{\'e} Augusto and Batista, Inez Staciarini",
                title = "Vertical ionization drift velocities and range type spread f in 
                         the evening equatorial ionosphere",
              journal = "Journal of Geophysical Research",
                 year = "1983",
               volume = "88",
               number = "A1",
                pages = "399--402",
                month = "Jan..",
             keywords = "AERONOMIA, propaga{\c{c}}{\~a}o F, ionogramas, equador 
                         magn{\'e}tico, spreed F, ionograms, magnetic equator.",
             abstract = "Range type spread F indices in the post sunset hours, determined 
                         from ionograms, are compared with F layer vertical velocities, 
                         also deduced from ionograms, for a period of one year, over the 
                         magnetic equatorial station Fortaleza (geographic coordinates: 4 
                         degree S, 38 degree W; dip latitude: 1.8 degree S), Brazil. 
                         Besides good correlation between the two parameters, the results 
                         suggest the presence of a certain threshold value for the vertical 
                         ionization velocity and a corresponding threshold height for the 
                         base of the evening F layer,- as one of the necessary conditions 
                         for the occurrence of spread F irregularities valid for southern 
                         solstice (summer)and equinoctial months. The nature of the 
                         possible variabilities in the amplitude of the initial 
                         perturbation in the ionization (seeding mechanism), which is 
                         another prerequisite for the generation of irregularities, is 
                         discussed briefly.",
                 issn = "0148-0227 and 2156-2202",
                label = "9453",
           targetfile = "8429.pdf",
        urlaccessdate = "15 jan. 2021"