@Article{AbduSoKhBaMaSo:2015:WaStPo,
author = "Abdu, Mangalathayil Ali and Souza, Jonas Rodrigues de and Kherani,
Esfhan Alam and Batista, Inez Staciarini and MacDougall, J. W. and
Sobral, Jos{\'e} Humberto Andrade",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto
Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and {Instituto Nacional de Pesquisas
Espaciais (INPE)} and {University of Western Ontario} and
{Instituto Nacional de Pesquisas Espaciais (INPE)}",
title = "Wave structure and polarization electric field development in the
bottomside F layer leading to postsunset equatorial spread F",
journal = "Journal of Geophysical Research: Space Physics",
year = "2015",
volume = "120",
number = "8",
pages = "6930--6910",
month = "Aug.",
keywords = "electric field, equatorial spread F, gravity waves, large-scale
wave structure, PRE vertical drift, prereversal vertical drift.",
abstract = "In this paper we present the results of a study on the
characteristics of large-scale wave structure in the equatorial
ionospheric F region that serve as precursor to postsunset
development of the spread F/plasma bubble irregularities. The
study is based on analysis of Digisonde data from three equatorial
sites in Brazil (Fortaleza, Sao Luis, and Cachimbo) for a period
of about 2 months at a medium solar activity phase.
Small-amplitude oscillations in the F layer heights, extracted at
a number of plasma frequencies, present characteristics as them
being generated from upward propagating gravity waves. They
represent wave structures in polarization electric field having
zonal scale of a few hundred kilometers. Their amplitudes in the
afternoon hours undergo amplification toward evening, leading to
postsunset development of equatorial spread F/plasma bubble
irregularities, on a statistical basis. On the days of their
larger amplitudes they appear to occur in phase coherence on all
days, and correspondingly, the evening prereversal vertical drift
velocities are larger than on days of the smaller amplitudes of
the wave structure that appear at random phase on the different
days. The sustenance of these precursor wave structures is
supported by the relatively large ratio (approaching unity) of the
F region-to-total field line-integrated Pedersen conductivities as
calculated using the Sheffield University Plasmasphere-Ionosphere
Model simulation of the low-latitude ionosphere. The significant
amplification in the wave structure toward sunset and the {"}phase
coherent{"} nature of their occurrences on different days are
explained tentatively on the basis of the spatial resonance
mechanism.",
doi = "10.1002/2015JA021235",
url = "http://dx.doi.org/10.1002/2015JA021235",
issn = "2169-9402",
language = "en",
targetfile = "Abdu et al_2015Wave structures-1.pdf",
urlaccessdate = "02 maio 2024"
}