@MastersThesis{Abaidoo:2022:ObIRMo,
author = "Abaidoo, Samuel",
title = "Space weather effects on the brazilian equatorial spread F:
observation and IRI model",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2022",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2021-06-28",
keywords = "equatorial ionosphere, equatorial spread-F, solar wind, digisonde,
solar minimum, ionosfera equatorial, equatorial spread-F, vento
solar, m{\'{\i}}nimo solar, clima espacial.",
abstract = "This work present the study of the Brazilian Equatorial spread-F
during the solar minimum year,2018. For this purpose, ionospheric
data obtained by a Digisonde installed in Belem, PA (BL; 48W,
1.43S; Dip: -2.6) were analyzed. Spread-F is the generic term
referring to plasma density fluctuations in the ionospheric
F-region after sunset. Its importance is attributed to its effects
on the radio waves propagation between satellites and ground-based
receivers, which in its turn affect global navigation and
positioning systems. In the Brazilian sector, characterized by a
large negative declination angle of magnetic equator, it is
observed a high occurrence of equatorial spread-F/equatorial
plasma bubbles. The interest on to study spread-F on solar minimum
is that there are no intense geomagnetic disturbances. In general,
weak-to-moderate storms mostly driven by High-Speed Solar wind
streams, HSSs, and Corotating Interaction region, CIRs occurr.
These storms are weaker than those driven by Coronal Mass
Ejections, CMEs. However, they present a long-duration recovery
phase. This {"}quiescent{"} scenario provides good conditions to
analyze the ionospheric response. The equatorial spread-F
occurrence rate was determined after analyzing thousands of
ionograms provided by the Digisonde installed at Belem and a
statistical study of was performed. At first, the spread-F was
classified in three main patterns: Range, Frequency, and Mixed
spread-F. The start time and duration of spread-F were also
evaluated for each night of the year. It was observed a seasonal
variation, with peaks in Summer solstice and Equinoxes, and a
minimum occurrence in June Solstice. The onset time was mostly at
around 21:00 LT, and it was noticed that spread-F duration time is
higher in Summer and Equinoxes than in June Solstice. The spread-F
probability was additionally calculated by the IRI model for each
hour in each month. It was noticed that there is a similar trend
for observed and calculated probability. However, some some
discrepancies were observed during disturbed intervals: IRI model
may underestimate or overestimate the spread-F probability. The
spread-F day-to-day variability was also considered. It was
observed that spread-F during solar minimum can occur during quiet
or disturbed geomagnetic intervals with variable duration.
However, under some moderate disturbed conditions, spread-F can be
suppressed or favored. In this way, the influence of a moderate
geomagnetic storm on the equatorial F-region heights and
frequencies was carefully investigated by the analyzes of
ionospheric parameters such as the virtual F-layer height, hIF;
the F-layer peak height, hmF2, and the critical plasma frequency,
foF2. It was selected a disturbed geomagnetic interval in May, a
month considered out of the Spread-F season in Brazil for a study
case. It was observed that during the main phase of the storm, the
F-region experienced a sudden uplift associated with an
intensified ExB vertical drift at nighttime. This uplift was
probably caused by enhanced zonal electric field associated to a
Prompt Penetration of Electric Field, PPEF. In its turn, the
plasma density was intensified over its five quietest days
average, 5QD, for some days of the recovery phase. These finding
can contribute to a better understanding of the ionosphere during
solar minimum a to Space Weather prediction programs. RESUMO: Este
trabalho apresenta o estudo do spread-F equatorial na regi{\~a}o
brasileira durante o m{\'{\i}}nimo solar 2018. Para tanto, foram
analisados dados ionosf{\'e}ricos obtidos por uma Digissonda
instalada em Bel{\'e}m, PA (BL; 48W, 1.43S; Dip: -2.6). Spread-F
{\'e} o termo gen{\'e}rico que se refere {\`a}s
flutua{\c{c}}{\~o}es da densidade do plasma na regi{\~a}o F
ionosf{\'e}rica ap{\'o}s o p{\^o}r do sol, as chamadas
irregularidades do plasma ionosf{\'e}rico equatorial, ou Bolhas
de plasma equatoriais. Sua import{\^a}ncia se deve aos seus
efeitos na propaga{\c{c}}{\~a}o das ondas de r{\'a}dio entre
sat{\'e}lites e receptores terrestres, e portanto, nos sistemas
globais de navega{\c{c}}{\~a}o e posicionamento. No setor
brasileiro, caracterizado por um grande {\^a}ngulo de
declina{\c{c}}{\~a}o negativo do equador magn{\'e}tico,
observa-se uma alta taxa de ocorr{\^e}ncia de spread-F/bolhas de
plasma equatorial. Neste trabalho estuda-se o spread-F equatorial
durante um ano de m{\'{\i}}nimo solar,o qual {\'e}
caracterizado pelo baixo n{\'u}mero de manchas e regi{\~o}es
ativas no Sol, bem como valores menores de fluxo solar. Neste
per{\'{\i}}odo, tempestades geomagn{\'e}ticas intensas n{\~a}o
s{\~a}o esparsas, enquanto tempestades fracas a moderadas
s{\~a}o frequentes. Tais tempestades geomagn{\'e}ticas s{\~a}o
principalmente geradas por fluxos de vento solar de alta
velocidade, HSSs (High-Speed Solar Wind Streams), e regi{\~o}es
de intera{\c{c}}{\~a}o corrotante, CIRs (Corotating Interaction
Regions). Embora essas tempestades sejam menos intensas do que as
provocadas por Eje{\c{c}}{\~o}es de Massa Coronal, CMEs (Coronal
Mass Ejections), elas apresentam uma fase de
recupera{\c{c}}{\~a}o de longa dura{\c{c}}{\~a}o (v{\'a}rios
dias), o que causa respostas ionosf{\'e}ricas de longa
dura{\c{c}}{\~a}o. A taxa de ocorr{\^e}ncia do spread-F
equatorial foi realizado ap{\'o}s a an{\'a}lise de milhares de
ionogramas fornecidos pela Digissonda instalada em Bel{\'e}m. O
spread-F foi classificado em tr{\^e}s padr{\~o}es principais:
Range, Frequency e Misto (uma combina{\c{c}}{\~a}o de ambos).
Caracter{\'{\i}}sticas como a hora de in{\'{\i}}cio e fim e a
dura{\c{c}}{\~a}o do spread-F foram avaliadas para cada noite do
ano. O estudo estat{\'{\i}}stico mostrou que h{\'a} uma uma
varia{\c{c}}{\~a}o sazonal, com picos de ocorr{\^e}ncia entre
os equin{\~o}cios no hemisf{\'e}rio sul, e m{\'{\i}}nimo
durante o solst{\'{\i}}cio de inverno. Em geral, o hor{\'a}rio
de in{\'{\i}}cio do spread-F foi principalmente por volta das
21:00 hora local. Adicionalmente, observou-se que que o tempo de
dura{\c{c}}{\~a}o do spread-F foi maior durante os meses de
ver{\~a}o e equin{\'o}cios do que no solst{\'{\i}}cio de
inverno. A probabilidade de ocorr{\^e}ncia do Spread-F foi
calculada baseada nas observa{\c{c}}{\~o}es e foi calculada pelo
modelo IRI para cada m{\^e}s. Observou-se que existe uma
tend{\^e}ncia similar para as probabilidades observada e a
calculada, embora com algumas discrep{\^a}ncias do modelo IRI, o
qual pode subestimar ou superestimar o spread-F observado
especialmente em per{\'{\i}}odos perturbados. A variabilidade
di{\'a}ria do spread-F tamb{\'e}m foi considerada na
an{\'a}lise. Foi observado que o spread-F durante o
m{\'{\i}}nimo solar pode ocorrer durante per{\'{\i}}odos
geomagneticamente calmos ou perturbados, com dura{\c{c}}{\~a}o
vari{\'a}vel. No entanto, sob algumas condi{\c{c}}{\~o}es
geomagneticamente moderadas, o spread-F pode ser favorecid em
per{\'{\i}}odos n{\~a}o usuais. A influ{\^e}ncia de uma
tempestade geomagn{\'e}tica moderada no spread-F foi investigada
pela an{\'a}lise de par{\^a}metros ionosf{\'e}ricos como a
altura virtual da camada F, hIF, a altura do pico da camada F,
hmF2 e a frequ{\^e}ncia cr{\'{\i}}tica do plasma, foF2. O
intervalo geomagneticamente perturbado foi o m{\^e}s de maio, um
m{\^e}s considerado fora da {"}temporada de spread-F no Brasil.
Foi percebido que durante a fase principal da tempestade a
regi{\~a}o F experimentou uma eleva{\c{c}}{\~a}o r{\'a}pida
associada a uma intensifica{\c{c}}{\~a}o do campo el{\'e}trico
e consequentemente da deriva vertical ExB durante a noite,
provavelmente causada por um epis{\'o}dio de
penetra{\c{c}}{\~a}o s{\'u}bita de campo el{\'e}trico, PPEF
(Prompt Penetration Electric Field). Al{\'e}m disso, a
frequ{\^e}ncia/densidade do plasma foi intensificada acima da
m{\'e}dia dos cinco dias mais calmos de maio (5QD) durante a fase
de recupera{\c{c}}{\~a}o. Estes resultados podem contribuir para
estudos dos efeitos de Clima Espacial em baixa atividade solar.",
committee = "Saba, Marcelo Magalh{\~a}es Fares (presidente), and C{\^a}ndido,
Claudia Maria Nicoli (orientadora), and Guedes, F{\'a}bio Becker
(orientador), and Odriozola, Siomel Savio and Klausner,
Virg{\'{\i}}nia",
englishtitle = "Efeitos do clima espacial na propaga{\c{c}}{\~a}o equatorial
brasileira F: modelo de observa{\c{c}}{\~a}o e IRI",
language = "en",
pages = "82",
ibi = "8JMKD3MGP3W34T/4559JM2",
url = "http://urlib.net/ibi/8JMKD3MGP3W34T/4559JM2",
targetfile = "publicacao.pdf",
urlaccessdate = "25 jun. 2024"
}