@Article{AbduKhBaPaFrSo:2009:GrWaIn,
               author = "Abdu, Mangalathayil Ali and Kherani, E. Alam and Batista, I. S. 
                         and Paula, E. R. and Fritts, D. C. and Sobral, J. H. A.",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {} and 
                         {Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and NorthWest Research 
                         Associates, Colorado Research Associates Division, Boulder, USA 
                         and {Instituto Nacional de Pesquisas Espaciais (INPE)}",
                title = "Gravity wave initiation of equatorial spread F/plasma bubble 
                         irregularities based on observational data from the SpreadFEx 
                         campaign",
              journal = "Annales Geophysicae",
                 year = "2009",
               volume = "27",
               number = "7",
                pages = "2607--2622",
             keywords = "Ionosphere, Ionospheric irregularities, Plasma waves and 
                         instabilities, RAYLEIGH-TAYLOR INSTABILITY, F EXPERIMENT 
                         SPREADFEX, REGION PLASMA DRIFTS, NONLINEAR EVOLUTION, 
                         ELECTRIC-FIELD, VERTICAL DRIFT, WINDS, IONOSPHERE, GENERATION, 
                         FORTALEZA.",
             abstract = "The data from ground based experiments conducted during the 2005 
                         SpreadFEx campaign in Brazil are used, with the help of 
                         theoretical model calculations, to investigate the precursor 
                         conditions, and especially, the role of gravity waves, in the 
                         instability initiation leading to equatorial spread F development. 
                         Data from a digisonde and a 30MHz coherent back-scatter radar 
                         operated at an equatorial site, Sao Luis (dip angle: 2.7 degrees) 
                         and from a digisonde operated at another equatorial site (dip 
                         angle: -11.5 degrees) are analyzed during selected days 
                         representative of differing precursor conditions of the evening 
                         prereversal vertical drift, F layer bottom-side density gradients 
                         and density perturbations due to gravity waves. It is found that 
                         radar irregularity plumes indicative of topside bubbles, can be 
                         generated for precursor vertical drift velocities exceeding 30 m/s 
                         even when the precursor GW induced density oscillations are 
                         marginally detectable by the digisonde. For drift velocities <= 20 
                         m/s the presence of precursor gravity waves of detectable 
                         intensity is found to be a necessary condition for spread F 
                         instability initiation. Theoretical model calculations show that 
                         the zonal polarization electric field in an instability 
                         development, even as judged from its linear growth phase, can be 
                         significantly enhanced under the action of perturbation winds from 
                         gravity waves. Comparison of the observational results with the 
                         theoretical model calculations provides evidence for gravity wave 
                         seeding of equatorial spread F.",
                label = "self-archiving-INPE-MCTIC-GOV-BR",
             language = "en",
           targetfile = "angeo-27-2607-2009.pdf",
        urlaccessdate = "16 jun. 2024"
}