@Article{OnoharaBatiBati:2018:WaStOb,
author = "Onohara, Amelia Naomi and Batista, Inez Staciarini and Batista,
Paulo Prado",
affiliation = "{Ag{\^e}ncia Espacial Brasileira (AEB)} and {Instituto Nacional
de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)}",
title = "Wavenumber-4 structures observed in the low-latitude ionosphere
during low and high solar activity periods using FORMOSAT/COSMIC
observations",
journal = "Annales Geophysicae",
year = "2018",
volume = "36",
number = "2",
pages = "459--471",
month = "Mar.",
keywords = "Ionosphere (equatorial ionosphere).",
abstract = "The main purpose of this study is to investigate the four-peak
structure observed in the low-latitude equatorial ionosphere by
the FORMOSAT/COSMIC satellites. Longitudinal distributions of NmF2
(the density of the F layer peak) and hmF2 (ionospheric F2-layer
peak height) averages, obtained around September equinox periods
from 2007 to 2015, were submitted to a bi-spectral Fourier
analysis in order to obtain the amplitudes and phases of the main
waves. The four-peak structure in the equatorial and low-latitude
ionosphere was present in both low and high solar activity
periods. This kind of structure possibly has tropospheric origins
related to the tidal waves propagating from below that modulate
the E-region dynamo, mainly the eastward nonmigrating diurnal tide
with wavenumber 3 (DE3, E for eastward). This wave when combined
with the migrating diurnal tide (DW1, W for westward) presents a
wavenumber4 (wave-4) structure under a synoptic view. Electron
densities observed during 2008 and 2013 September equinoxes
revealed that the wave-4 structures became more prominent around
or above the F-region altitude peak ( \∼ 300350 km). The
four-peak structure remains up to higher ionosphere altitudes
(\∼ 800 km). Spectral analysis showed DE3 and SPW4
(stationary planetary wave with wavenumber 4) signatures at these
altitudes. We found that a combination of DE3 and SPW4 with
migrating tides is able to reproduce the wave-4 pattern in most of
the ionospheric parameters. For the first time a study using wave
variations in ionospheric observations for different altitude
intervals and solar cycle was done. The conclusion is that the
wave-4 structure observed at high altitudes in ionosphere is
related to effects of the E-region dynamo combined with transport
effects in the F region.",
doi = "10.5194/angeo-36-459-2018",
url = "http://dx.doi.org/10.5194/angeo-36-459-2018",
issn = "0992-7689",
language = "en",
targetfile = "onohrara_wavenumber.pdf",
urlaccessdate = "27 abr. 2024"
}