@Article{EssienFTWBKLAGB:2021:LoStMe,
author = "Essien, Patrick and Figueiredo, Cosme Alexandre Oliveira Barros
and Takahashi, Hisao and Wrasse, Cristiano Max and Barros, Diego
and Klutse, N. A. B. and Lomotey, Solomon Otoo and Ayorinde,
Toyese Tunde and Gobbi, Delano and Bilibio, Anderson Vestena",
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 {Instituto Nacional de Pesquisas Espaciais
(INPE)} and {African Institute for Mathematical Sciences (AIMS)}
and {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)}",
title = "Long-term study on medium-scale traveling ionospheric disturbances
observed over the south american equatorial region",
journal = "Atmosphere",
year = "2021",
volume = "12",
number = "11",
pages = "e1409",
month = "Nov.",
keywords = "Detrended TEC, Equatorial, Medium-scale traveling ionospheric
disturbances.",
abstract = "Using data collected by the GNSS dual-frequency receivers network,
de-trended TEC maps were generated to identify and characterize
the medium-scale traveling ionospheric disturbances (MSTIDs) over
the South American equatorial region (latitude: 0\◦ to
15\◦ S and longitude: 30\◦ to 55\◦ W) during
solar cycle 24 (from January 2014 to December 2019). A total of
712 MSTIDs were observed during quiet geomagnetic conditions. The
Frequency of occurrence of MSTID is high during the solar maximum
and low in the minimum phase. This might be due to the solar cycle
dependence of gravity wave activity in the lower atmosphere and
gravity wave propagation conditions in the thermosphere. The
predominant daytime MSTIDs, representing 80% of the total
observations, occurred in winter (June-August season in the
southern hemisphere) with the secondary peak in the equinox; while
the evening time MSTIDs, representing 18% of the entire events,
occurred in summer (December to February season) and equinox
(March to May and September to November), and the remaining 2% of
the MSTIDs were observed during nighttime. The seasonal variation
of the MSTID events was attributed to the source mechanisms
generating them, the wind filtering and dissipation effects, and
the local time dependency. The horizontal wavelengths of the
MSTIDs were mostly concentrated between 500 and 800 km, with the
mean value of 667 ± 131 km. The observed periods ranged from 30 to
45 min with the mean value of 36 ± 7 min. The observed horizontal
phase speeds were distributed around 200 to 400 m/s, with the
corresponding mean of 301 ± 75 m/s. The MSTIDs in the winter
solstice and equinoctial months preferentially propagated
northeastward and northwestward. Meanwhile, during the summer
solstice, they propagated in all directions. The anisotropy of the
propagation direction might be due to several reasons: the wind
and dissipative filtering effects, ion drag effects, the primary
source region, and the presence of the secondary or tertiary
gravity waves in the thermosphere. Atmospheric gravity waves from
strong convective sources might be the primary precursor for the
observed equatorial MSTIDs. In all seasons, we noted that the
MSTIDs propagating southeastward were probably excited by the
likely gravity waves generated by the intertropical convergence
zone (ITCZ).",
doi = "10.3390/atmos12111409",
url = "http://dx.doi.org/10.3390/atmos12111409",
issn = "2073-4433",
language = "en",
targetfile = "essien_atmosphere.pdf",
urlaccessdate = "2024, May 05"
}