@PhDThesis{Yamashita:2015:VaLoPe,
author = "Yamashita, Cristina Sayuri",
title = "Variabilidade de longo per{\'{\i}}odo da camada F2 no setor
sul-americano",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2015",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2015-08-25",
keywords = "variabilidade solar e ionosf{\'e}rica, efeitos no clima espacial,
ionossonda, digissonda, modelo climatol{\'o}gico, ionospheric and
solar variability, effect on space weather, ionosonde, digisonde,
climatological model.",
abstract = "Nesta Tese de Doutorado, estudou-se a variabilidade de longo
per{\'{\i}}odo do pico da ionosfera (camada F2) de baixa
latitude e da regi{\~a}o equatorial do setor sul-americano
baseado nos par{\^a}metros foF2, hpF2 e hmF2 obtidos atrav{\'e}s
dos registros de sondagem ionosf{\'e}ricas dos s{\'{\i}}tios de
Cachoeira Paulista (22,67\$^{o}\$ S, 44,99\$^{o}\$ O) e
Fortaleza (3,71\$^{o}\$ S, 38,54\$^{o}\$ O), em
condi{\c{c}}{\~o}es geomagneticamente calmas e {\`a}s 12 horas
LT. Criaram-se modelos emp{\'{\i}}ricos baseados nos principais
for{\c{c}}antes de produ{\c{c}}{\~a}o de pares de {\'{\i}}ons
diurnos, isto {\'e}, na varia{\c{c}}{\~a}o de incid{\^e}ncia
de radia{\c{c}}{\~a}o solar ao longo dos anos. Para tal,
estudaram-se as varia{\c{c}}{\~o}es nos {\'u}ltimos 4 ciclos
solares (desde 1970) dos par{\^a}metros solares: {\'{\i}}ndice
do n{\'u}mero de manchas solares, fluxo de r{\'a}dio solar em
10,7 cm (F10,7) e radia{\c{c}}{\~a}o no extremo ultravioleta em
duas bandas (26-34 nm e 0,1-50 nm) medidas pelo instrumento
SOHO/SEM. Resultados obtidos das analises hist{\'o}ricas do fluxo
de radia{\c{c}}{\~a}o solar mostram que a radia{\c{c}}{\~a}o
EUV emitida sofreu uma redu{\c{c}}{\~a}o de aproximadamente
25\% no ciclo \#24 quando comparado ao ciclo \#23 (tendo como
base o per{\'{\i}}odo de baixa atividade solar). Estes
resultados indicam uma tend{\^e}ncia de diminui{\c{c}}{\~a}o na
quantidade de irradi{\^a}ncia solar incidente na atmosfera
terrestre, o que teria implica{\c{c}}{\~o}es para a
produ{\c{c}}{\~a}o de {\'{\i}}ons por
fotoioniza{\c{c}}{\~a}o. Atrav{\'e}s do estudo da variabilidade
dos par{\^a}metros ionosf{\'e}ricos (excluindo a sua
autovaria{\c{c}}{\~a}o devido a deposi{\c{c}}{\~a}o de energia
solar atrav{\'e}s da incid{\^e}ncia de radia{\c{c}}{\~a}o),
constatou-se que a quantidade de el{\'e}trons do pico da
ionosfera acima de Cachoeira Paulista (baseado no par{\^a}metro
foF2) diminuiu aproximadamente \$\sim\$-20\% no
per{\'{\i}}odo de inverno do hemisf{\'e}rio sul e aumentou em
torno de \$\sim\$15\% no per{\'{\i}}odo de ver{\~a}o,
apesar da tend{\^e}ncia negativa de decr{\'e}scimo da respectiva
altitude do pico (par{\^a}metros hpF2 e hmF2). Tal comportamento
aponta para a poss{\'{\i}}vel varia{\c{c}}{\~a}o da escala de
altura do oxig{\^e}nio at{\^o}mico ao longo dos anos, e que esta
variabilidade {\'e} fortemente modulada pelo per{\'{\i}}odo do
ano. Para Fortaleza, notou-se que o par{\^a}metro foF2 teve uma
tend{\^e}ncia positiva entre 13-24\% para quase todo o ano. Os
par{\^a}metros hpf2, hmf2 mostraram tend{\^e}ncia negativa de
\$\sim\$-11-14\% em julho, positiva de \$\sim\$+10-18\% no
ver{\~a}o e equin{\'o}cios. ABSTRACT: In this thesis, the long
term variability of the peak of the ionosphere (F2 layer) at
low-latitude and equatorial regions of the South American sector
is studied. This work is based on foF2, hpF2 and hmF2 parameters
obtained through the ionospheric sounding records of the sites
from Cachoeira Paulista (22,67\$^{o}\$ S, 44,99\$^{o}\$ O) and
Fortaleza (3,71\$^{o}\$ S, 38,54\$^{o}\$ O). Data during quiet
geomagnetic conditions at 12 LT (Local Time) were studied.
Empirical models were created based on the main forcing production
of diurnal ion pairs, that is, variation in the incidence of solar
radiation over the years. In order to perform this study, the
variations in solar parameters over the past four solar cycles
(since 1970) have been studied: the index number of sunspots,
solar radio flux at 10.7 cm (F10.7) and extreme ultraviolet
radiation in two bands (26-34 nm and 0.1-50 nm) measured by
SOHO/SEM instrument. Results of the historical analysis of the
solar radiation flux show that the EUV radiation was reduced by
approximately 25\% in the cycle \# 24 compared to the cycle \#
23. These results indicate a decreasing trend in the quantity of
incident solar irradiance at the Earth\${}\$s atmosphere, which
would have implications for the production of ions by
photoionization. Through the study of variation of ionospheric
parameters (excluding the auto variation due to deposition of
solar energy by radiation incidence) it was found that the amount
of peak electrons of the ionosphere above Cachoeira Paulista
(based on foF2 parameter) decreased approximately
\$\sim\$-20\% during the southern hemisphere winter and
increased by around \$\sim\$ -15\% during the summer. Such
behavior indicates the range of possible variation in height of
the atomic oxygen over the years, and this variability is strongly
modulated by the period of the year. For Fortaleza, it was noted
that the parameter foF2 showed a positive trend between 13-24\%
for most of the year. The parameters hpf2, hmF2 showed a negative
trend of \$\sim\$ -11-14\% in July, and a positive trend of
\$\sim\$ +10-18\% in summer and equinoxes.",
committee = "Dal Lago, Alisson (presidente) and Echer, Ezequiel (orientador)
and Echer, Mariza Pereira de Souza (orientadora) and Alarcon,
Alicia Luisa Cl{\'u}a de Gonzalez and Sobral, Jos{\'e} Humberto
Andrade and Pacini, Alessandra Abe and Bertoni, Fernando Celso
Perin",
copyholder = "SID/SCD",
englishtitle = "Long term variability of F2 layer in the South American sector",
language = "pt",
pages = "119",
ibi = "8JMKD3MGP3W34P/3K5FA2L",
url = "http://urlib.net/ibi/8JMKD3MGP3W34P/3K5FA2L",
targetfile = "publicacao.pdf",
urlaccessdate = "25 abr. 2024"
}