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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Wavenumber-4 structures observed in the low-latitude ionosphere during low and high solar activity periods using FORMOSAT/COSMIC observations

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Onohara, Amelia Naomi [1] ; Batista, Inez Staciarini [2] ; Batista, Paulo Prado [2]
Total Authors: 3
[1] Brazilian Space Agcy, SPO Sul, Area 5, Quadra 3, Bloco A, BR-70610200 Brasilia, DF - Brazil
[2] Natl Inst Space Res, Av Astronautas, 1758, Jd Granja, BR-12227010 Sao Jose Dos Campos, SP - Brazil
Total Affiliations: 2
Document type: Journal article
Source: Annales Geophysicae; v. 36, n. 2, p. 459-471, MAR 21 2018.
Web of Science Citations: 1

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 non-migrating diurnal tide with wavenumber 3 (DE3, ``E{''} for eastward). This wave when combined with the migrating diurnal tide (DW1, ``W{''} for westward) presents a wavenumber-4 (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 (similar to 300-350 km). The four-peak structure remains up to higher ionosphere altitudes (similar to 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. (AU)

FAPESP's process: 11/11071-0 - Study and characterization of the longitudinal four peaks structure present in observations of the equatorial anomaly ionization performed by satellite
Grantee:Amelia Naomi Onohara
Support Opportunities: Scholarships in Brazil - Post-Doctorate