author = "Abdu, Mangalathayil Ali and Kherani, Esfhan Alam and Sousasantos, 
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Tecnol{\'o}gico de Aeron{\'a}utica (ITA)}",
                title = "Role of bottom-side density gradient in the development of 
                         equatorial plasma bubble/spread F irregularities: solar minimum 
                         and maximum conditions",
              journal = "Journal of Geophysical Research: Space Physics",
                 year = "2020",
               volume = "125",
               number = "10",
                pages = "e2020JA027773",
                month = "Oct",
             abstract = "From the analysis of Digisonde data over Brazilian equatorial and 
                         low\‐latitude sites, we investigate the relative importance 
                         of the different parameters driving the generation of rising 
                         bubble\‐type and bottom\‐type spread F (SF) 
                         irregularities. Data for the complete month of October 2001, a 
                         solar maximum epoch (F10.7 = 210), and that of October 2008, an 
                         extended solar minimum period (F10.7 = 70), are analyzed to 
                         examine the SF intensity and occurrence rate as a function of the 
                         evening prereversal vertical drift velocity and the corresponding 
                         F layer heights and the bottom\‐side density gradient. 
                         While the SF at the equatorial site is indicative of both the 
                         bottom\‐side irregularities and rising bubbles, the SF at 
                         the low latitude represents exclusively the latter. Comparison of 
                         the results, from the two epochs, reveals a large decrease in the 
                         intensity and occurrence rate of plasma bubbles, with a decrease 
                         in solar flux. But a notable increase in these characteristics is 
                         observed in the case of bottom\‐side SF. It is found that a 
                         larger (steeper) density gradient of the F layer bottom side that 
                         exists in the low solar flux condition is responsible for an 
                         enhanced Raleigh\‐Taylor instability growth, 
                         counterbalancing a reduction in this rate that may arise from a 
                         smaller prereversal vertical drift and lower layer height that 
                         also characterize the low solar flux condition. Thus, the role of 
                         the bottom\‐side density gradient in the ESF instability 
                         growth has been identified for the first time in terms of its 
                         ability to explain the contrasting irregularity features as 
                         observed during solar flux maximum and minimum years.",
                  doi = "10.1029/2020JA027773",
                  url = "http://dx.doi.org/10.1029/2020JA027773",
                 issn = "2169-9402",
             language = "en",
           targetfile = "abdu_role.pdf",
        urlaccessdate = "11 abr. 2021"