@PhDThesis{Negreti:2012:EsCoEl,
author = "Negreti, Patr{\'{\i}}cia Mara de Siqueira",
title = "Estudo do conte{\'u}do eletr{\^o}nico total na regi{\~a}o
brasileira em per{\'{\i}}odos magneticamente perturbados",
school = "Instituto Nacional de Pesquisas Espaciais",
year = "2012",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2012-03-28",
keywords = "conte{\'u}do eletr{\^o}nico total, ionosfera, tempestades
magn{\'e}ticas, Sistema de Posicionamento Global (GPS), total
electron content, ionosphere, magnetic storms, Global Positioning
System (GPS).",
abstract = "Neste trabalho foram estudadas as respostas ionosf{\'e}ricas aos
eventos de tempestades magn{\'e}ticas intensas e muito intensas
(super tempestades) ocorridas entre 2001 e 2006. O par{\^a}metro
estudado foi o Conte{\'u}do Eletr{\^o}nico Total (TEC), que
retrata a din{\^a}mica ionosf{\'e}rica durante as
perturba{\c{c}}{\~o}es magn{\'e}ticas. Nos eventos estudados
neste trabalho, foi poss{\'{\i}}vel verificar a fase positiva da
tempestade ionosf{\'e}rica, em que a caracter{\'{\i}}stica
principal foram os aumentos no TEC devido aos campos
el{\'e}tricos de penetra{\c{c}}{\~a}o, inclusive com
estabelecimento de um efeito fonte intensificado que resulta em um
desenvolvimento da anomalia equatorial com cristas mais
proeminentes e deslocadas para maiores latitudes. Foram observadas
tamb{\'e}m a fase negativa da tempestade ionosf{\'e}rica, em que
campos el{\'e}tricos de d{\'{\i}}namo perturbado e
modifica{\c{c}}{\~o}es na composi{\c{c}}{\~a}o neutra causam
diminui{\c{c}}{\~o}es no TEC, e a fase de
recupera{\c{c}}{\~a}o, em que os n{\'{\i}}veis do TEC
gradualmente retomam os valores do per{\'{\i}}odo calmo. A
deriva vertical ionosf{\'e}rica sobre o equador geomagn{\'e}tico
foi simulada utilizando uma rede neural baseada no m{\'e}todo de
magnet{\^o}metros, utilizando a diferen{\c{c}}a
\$\bigtriangleup\$\textit{H}, que fornece uma
aproxima{\c{c}}{\~a}o real{\'{\i}}stica do comportamento da
deriva vertical ionosf{\'e}rica diurna, devido {\`a}s
varia{\c{c}}{\~o}es observadas no eletrojato equatorial. Dessa
forma, as derivas verticais diurnas foram simuladas em Jicamarca,
no Brasil e nas Filipinas, para os per{\'{\i}}odos de
tempestades magn{\'e}ticas estudados nesse trabalho. As
varia{\c{c}}{\~o}es longitudinais observadas nas derivas e as
respostas no TEC foram examinadas nessas tr{\^e}s localidades. As
derivas verticais diurnas simuladas foram utilizadas para calcular
o campo el{\'e}trico zonal, denominado \$E_{yIONO}\$ \\&
neste trabalho, e examinar os eventos de penetra{\c{c}}{\~a}o de
campos el{\'e}tricos, em que o campo zonal apresenta assinatura
semelhante ao campo el{\'e}trico interplanet{\'a}rio
(\$E_{yIEF}\$). Foram observados eventos em que o
\$E_{yIONO}\$ apresentou assinatura semelhante ao \$E_{yIEF}\$
durante 2 e 7 horas seguidas, por{\'e}m n{\~a}o foi
poss{\'{\i}}vel concluir neste trabalho que ocorreu um evento de
penetra{\c{c}}{\~a}o de longa dura{\c{c}}{\~a}o, pois as
incurs{\~o}es negativas do \$E_{yIEF}\$ n{\~a}o s{\~a}o
transmitidas com a mesma efici{\^e}ncia ao plano equatorial como
ocorre nas incurs{\~o}es positivas. Dessa forma, os valores
negativos do \$E_{yIEF}\$, que resultam de uma incurs{\~a}o
para norte da componente \$B_{z}\$ do campo magn{\'e}tico
interplanet{\'a}rio, n{\~a}o foram observados serem transmitidos
ao plano equatorial. Assim, neste trabalho assumiu-se que
ocorreram eventos de \textit{overshielding} durante as
incurs{\~o}es para norte de \$B_{z}\$. A incurs{\~a}o negativa
mais intensa da componente \$B_{z}\$ observada neste trabalho
(-52,2 nT) resultou na tempestade magn{\'e}tica mais intensa
(Sym-H = -490 nT), resultando tamb{\'e}m nas
modifica{\c{c}}{\~o}es mais significativas no TEC, que
apresentou aumentos de aproximadamente 300 \%. Aumentos no TEC
durante a ocorr{\^e}ncia de um Evento HILDCAA (\textit{High
Intensity Long Duration Continuous AE Activity}) foram observados,
em que os aumentos no TEC foram compat{\'{\i}}veis com os
observados durante as tempestades magn{\'e}ticas (\$\sim\$
100\%) e aumentos no {\'{\i}}ndice F10.7 durante a
ocorr{\^e}ncia de HILDCAA. O aumento no TEC durante esse
fen{\^o}meno foi associado ao aumento no {\'{\i}}ndice F10.7.
Neste trabalho mostrou-se que o TEC responde majoritariamente
{\`a}s for{\c{c}}antes do vento solar, e mesmo na aus{\^e}ncia
de tempestades magn{\'e}ticas, como durante o evento HILDCAA
observado, as modifica{\c{c}}{\~o}es nas for{\c{c}}antes do
vento solar s{\~a}o respons{\'a}veis por causar aumentos
significativos no TEC. ABSTRACT: This work presents a study of the
ionopheric response to intense and very intense magnetic storms
occurred from 2001 to 2006. The parameter studied here was the
Total Electron Content (TEC) which reveals the ionospheric dynamic
during geomagnetic disturbances. The events discussed in this
study present the well known phases of ionospheric storms. We
verified the positive phase of the ionospheric storm which
presents increases in TEC due to the prompt penetration electric
fields, and also the intensification of the fountain effect that
generates the equatorial anomaly with prominent crests displaced
to higher latitudes. The negative phase of the ionospheric storm
was also observed when disturbance dynamo electric fields and
changes in the neutral composition caused TEC decreases. The
recovery phase of the ionospheric storms observed in this study
showed the gradual recovery of TEC to quiet time values. The
vertical plasma drifts over the geomagnetic equator were simulated
using the dual magnetometer technique which provides a realistic
estimate of the daytime vertical drift based on the equatorial
electrojet variations. The vertical drifts were simulated for
Peru, Brazil and Philippine sectors for the periods of the
magnetic storms studied in this work. The longitudinal differences
observed in the responses by the vertical drifts and the TEC were
analyzed using the data from the three locations. The simulated
vertical drifts were used to calculate the zonal electric field,
denoted as \$E_{yIONO}\$ in this study, in order to verify the
occurrence of penetration electric fields. During events of
penetration electric fields the zonal electric field and the
interplanetary electric field (IEF) present similar signatures. We
verified similarities between \$E_{yIONO}\$ and \$E_{yIEF}\$
lasting from 2 to 7 hours but it was not possible to attribute
them to long duration penetration electric fields. The reason is
that the negative incursions of \$E_{yIEF}\$ were not
transmitted to the equatorial plane with the same efficiency
observed during the positive incursions. For that reason the
negative incursions of \$E_{yIEF}\$ (occurred during northward
incursions of the interplanetary magnetic field \$B_{z}\$) and
the resulting negative vertical drifts observed over the
geomagnetic equator were attributed to \textit{overshielding}
events. The most negative magnitude of IMF \$B_{z}\$ observed in
this study (-52.2 nT) resulted in the most intense magnetic storm
analyzed here (Sym-H = -490 nT) and also the most remarkable TEC
differences, which presented increases of about 300\% compared to
quiet time. One event of HILDCAA (High Intensity Long Duration
Continuous AE Activity) phenomenon was observed and the TEC
increases during the HILDCAA event were comparable to the TEC
changes observed during magnetic storms (\$\sim\$100\%). The
main feature observed during the HILDCAA event was an increase in
the F10.7 index and this was probably the cause of the TEC
enhancements. In this work we show that TEC responds mostly to the
solar wind forcing and significant TEC changes may occur even in
the absence of magnetic storms as we could verify during the
HILDCAA event analyzed here.",
committee = "Batista, Inez Staciarini (presidente) and Kantor, Ivan Jelinek
(vice-presidente) and Paula, Eurico Rodrigues de (orientador) and
Abdu, Mangalathayil Ali (orientador) and Echer, Ezequiel and
Camargo, Paulo de Oliveira and Muella, Marcio Tadeu Assis
Honorato",
copyholder = "SID/SCD",
englishtitle = "Study of the total electron content over Brazilian region during
magnetically disturbed times",
language = "pt",
pages = "323",
ibi = "8JMKD3MGP7W/3BS8S7H",
url = "http://urlib.net/ibi/8JMKD3MGP7W/3BS8S7H",
targetfile = "publicacao.pdf",
urlaccessdate = "11 maio 2024"
}