Detalhes bibliográficos
| Ano de defesa: |
2020 |
| Autor(a) principal: |
Patrick Essien |
| Orientador(a): |
Hisao Takahashi,
Cosme Alexandre Oliveira Barros Figueiredo |
| Banca de defesa: |
Jonas Rodrigues de Souza,
Akeem Babatunde Rabiu,
Igo Paulino da Silva |
| Tipo de documento: |
Tese
|
| Tipo de acesso: |
Acesso aberto |
| Idioma: |
eng |
| Instituição de defesa: |
Instituto Nacional de Pesquisas Espaciais (INPE)
|
| Programa de Pós-Graduação: |
Programa de Pós-Graduação do INPE em Geofísica Espacial
|
| Departamento: |
Não Informado pela instituição
|
| País: |
BR
|
| Link de acesso: |
http://urlib.net/sid.inpe.br/mtc-m21c/2020/08.06.23.10
|
Resumo: |
Using data collected by GNSS (GPS and GLONASS specifically) dual frequency receivers network, detrended TEC maps were generated to identify and characterize the medium-scale traveling ionospheric disturbances (MSTIDs) over the South American equatorial region (latitude: 0 to 15S and longitude: 30 to 55W ) during solar cycle 24 (from January 2014 to December 2019). Among 742 MSTIDs that were observed, 712 of them representing 96% were observed during geomagnetic quiet condition and 30 events indication 4% were observed during geomagnetic disturbed condition. The observed MSTIDs show strong positive correlation with the solar activity. The positive correlation might have been caused by gravity waves dissipation due to high viscosity in the thermosphere as a result of low and high thermospheric temperature during solar minimum and maximum respectively. The predominant daytime MSTIDs representing 70% of the total observation occurred in winter with the secondary peak in equinox, while the evening time MSTIDs which is 28% of the entire events occurred in summer and equinox, while the remaining 2% of the MSTIDs were observed during nighttime. The local time dependency of the MSTIDs was attributed to the mechanisms generating them and/or the medium at which they propagated while the seasonal variation could be as results of wind filtering and dissipation effect during winter and summer. The horizontal wavelengths of the MSTIDs were concentrated between 300 and 1400 km, with the mean value of 667±131 km. The observed periods were ranging from 20 to 60 min with the mean value of 36±7 min. The observed horizontal phase speeds were distributed around 100 to 700 m/s, with the corresponding mean of 301±75 m/s. The MSTIDs in winter solstice and equinoctial months preferentially propagated northeastward and northwestward. Meanwhile, during 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 originated from the equatorial and Amazon region might be the primary precursor of the northeastward and northwestward propagating MSTIDs during summer solstice and autumn equinox. Nevertheless, strong cold front emanating from low latitude might have been the primary source for the northeastward and northwestward MSTIDs during winter solstice and spring equinox. In all the seasons, we noted that the MSTIDs propagating southeastward were probably excited by the likely gravity waves that was generated by the intertropical convergence zone (ITCZ). |
