@PhDThesis{Madsen:2009:InRáFe,
author = "Madsen, Felipe Ramos Hald",
title = "Investiga{\c{c}}{\~o}es r{\'a}dio-interferom{\'e}trica de
fen{\^o}menos solares e m{\'e}todo de calibra{\c{c}}{\~a}o
usando sat{\'e}lites de GPS",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2009",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2009-02-26",
keywords = "interferometria, explos{\~o}es solares, buracos coronais,
calibra{\c{c}}{\~a}o, r{\'a}dio-astronomia, interferometry,
solar flares, coronal holes, calibration, radio astronomy.",
abstract = "As explos{\~o}es solares e os buracos coronais s{\~a}o
fen{\^o}menos solares que est{\~a}o diretamente associados
{\`a} din{\^a}mica do campo magn{\'e}tico solar e que t{\^e}m
grande import{\^a}ncia para o Clima Espacial.
Observa{\c{c}}{\~o}es r{\'a}dio-interferom{\'e}tricas nas
bandas m{\'e}trica e decim{\'e}trica s{\~a}o contrapartidas
importantes em investiga{\c{c}}{\~o}es multi-espectrais destes
fen{\^o}menos pois {\'e} somente atrav{\'e}s do uso de
interfer{\^o}metros que podem ser atingidas, nestas faixas de
frequ{\^e}ncias, resolu{\c{c}}{\~o}es angulares
compar{\'a}veis {\`a}s dos observat{\'o}rios espaciais solares
de ultra-violeta e raios-X em opera{\c{c}}{\~a}o atualmente - da
ordem de segundos de arco. Neste contexto, o ``Giant Metrewave
Radio Telescope'' (GMRT) foi utilizado para a
realiza{\c{c}}{\~a}o das observa{\c{c}}{\~o}es de
explos{\~o}es solares e buracos coronais apresentadas neste
trabalho, respectivamente na banda de frequ{\^e}ncia dupla de
244/611 MHz, com resolu{\c{c}}{\~a}o angular de \$ \sim\$
60/20 e na banda de 157 MHz, com resolu{\c{c}}{\~a}o angular de
\$ \sim\$ 60. Nos mapas solares do GMRT, foram obtidas faixas
din{\^a}micas que variam entre 20:1 e 170:1, no caso de
imageamento instant{\^a}neo (``snapshot'') ou por
s{\'{\i}}ntese de rota{\c{c}}{\~a}o, respectivamente.
Atrav{\'e}s de investiga{\c{c}}{\~o}es multi-espectrais de um
buraco coronal observado com o GMRT em 04/06/2005, utilizando
imagens de r{\'a}dio em ondas m{\'e}tricas, ultravioleta extremo
e raios-X moles, foi poss{\'{\i}}vel obter as suas
caracter{\'{\i}}sticas morfol{\'o}gicas e determinar sua
temperatura e densidade eletr{\^o}nica, respectivamente \$ 7,7
\times 105\$ K e \$ 6,79 \times 107\$ cm\$ ^{-3}\$ . Por
outro lado, atrav{\'e}s de investiga{\c{c}}{\~o}es
multi-espectrais de uma explos{\~a}o solar observada com o GMRT
em 26/11/2005, utilizando imagens e curvas de luz em r{\'a}dio,
ultravioleta e raios-X moles, foi poss{\'{\i}}vel estimar que a
altura da regi{\~a}o onde a energia da explos{\~a}o foi liberada
{\'e} \$ \sim\$ 100 Mm acima da Fotosfera. Al{\'e}m disso,
atrav{\'e}s da an{\'a}lise de periodicidades nas curvas de luz
em r{\'a}dio utilizando transformada Morlet Wavelet, foi
detectada a ocorr{\^e}ncia de oscila{\c{c}}{\~o}es
ac{\'u}sticas com per{\'{\i}}odos de 187, 215 e 283 segundos,
indicando a presen{\c{c}}a de estruturas associadas a estas
oscila{\c{c}}{\~o}es com extens{\~o}es no intervalo 30 -- 50
Mm. As observa{\c{c}}{\~o}es solares interferom{\'e}tricas,
contudo, normalmente n{\~a}o s{\~a}o completamente calibradas
devido {\`a} falta de fontes calibradoras com fluxos da mesma
ordem ou maiores que o do Sol, e a principal
implica{\c{c}}{\~a}o disso {\'e} uma limita{\c{c}}{\~a}o na
qualidade das imagens solares interferom{\'e}tricas. Enquanto
isso, os sat{\'e}lites do Sistema de Posicionamento Global (GPS)
podem ser considerados fontes puntuais para a maior parte dos
interfer{\^o}metros solares em opera{\c{c}}{\~a}o atualmente,
com {\'o}rbitas bem conhecidas e fluxo na superf{\'{\i}}cie da
Terra com intensidade maior que a do fluxo solar em 1575 MHz.
Buscando obter mapas solares com qualidade ainda maior do que
aquela que pode ser obtida com as t{\'e}cnicas utilizadas
atualmente, um novo m{\'e}todo para calibra{\c{c}}{\~a}o de
observa{\c{c}}{\~o}es interferom{\'e}tricas solares {\'e}
proposto neste trabalho, utilizando os sat{\'e}lites de GPS como
fontes calibradoras. Este m{\'e}todo foi aplicado a
observa{\c{c}}{\~o}es solares realizadas com o prot{\'o}tipo do
``Brazilian Decimetric Array'' (PBDA) e os resultados obtidos
indicam que os sinais de sat{\'e}lites de GPS s{\~a}o adequados
para a calibra{\c{c}}{\~a}o de fontes de emiss{\~a}o muito
intensas, podendo ser aplicados a observa{\c{c}}{\~o}es solares
interferom{\'e}tricas. ABSTRACT: Solar flares and coronal holes
are solar phenomena that are directly associated with the dynamics
of the solar magnetic field and of great importance for Space
Weather. Radio interferometric observations in metric and
decimetric wavelengths are important counterparts to
multi-wavelength investigations of such phenomena as it is only
through interferometry that it is possible to achieve angular
resolutions of the order of seconds of arc, comparable to that of
the present solar observatories in space. In this sense, the
observations of solar flares and coronal holes presented in this
work were carried out with the Giant Metrewave Radio Telescope
(GMRT), respectively in the double frequency band at 244/611 MHz,
with angular resolution of \$ \sim\$ 60/20 and at 157 MHz, with
angular resolution of \$ \sim\$ 60. The dynamic ranges achieved
in the GMRT solar maps range between 20:1 and 170:1, respectively
for snapshots and apperture synthesis. Multi-wavelength
investigations of a coronal hole observed with GMRT on 06/04/2005
were carried out using solar images at meter wavelengths, extreme
ultraviolet and soft x-rays, leading to the morphology of the
coronal hole and the determination of its temperature and electron
density, respectively \$ 7.7 \times 10^{5}\$ K e \$ 6.79
\times 10^{7}\$ cm\$ ^{-3}\$ . On the other hand,
multi-wavelength investigations of a solar flare observed with
GMRT on 11/26/2005 were carried out using solar images and light
curves in metric and decimetric wavelengths, extreme ultraviolet
and soft x-rays, leading to an estimate that the site of energy
release in this flare was located \$ \sim\$ 100 Mm above the
solar photosphere. The radio light curves were also searched for
oscilation periods through it Morlet Wavelet transform, leading to
the detection of acoustic oscilattions with periods of 187, 215
and 283 seconds, indicating the presence of oscilation sources
extending in the range 30 -- 50 Mm. However, Solar interferometric
data are usually not uniquely and completely calibrated due to the
lack of calibrator sources with fluxes of the same order or higher
than that of the Sun, hence limiting the quality of the
interferometric solar maps. On the other hand, the satellites of
the Global Positioning System (GPS) can be regarded as point
sources for most of the solar-observing arrays, with well known
orbits and power transmitted, so that the resulting flux on
Earth's surface is higher than that of the Quiet Sun at 1575 MHz.
Aiming to obtain solar maps better than those obtained with
present techniques, a new method is proposed in this work, making
use of GPS satellites as calibrator sources. This calibration
technique was applied to solar observations using the prototype of
the Brazilian Decimetric Array (PBDA). The results indicate that
the GPS signals are adequate for calibration of very strong
sources and can be applied to interferometric solar
observations.",
committee = "Sawant, Hanumant Shankar (presidente/orientador) and Cecatto,
Jos{\'e} Roberto (orientador) and Costa, Joaquim Eduardo Rezende
and Fernandes, Francisco Carlos Rocha and Faria, Claudio and
L{\'e}pine, Jacques Raymond Daniel",
copyholder = "SID/SCD",
englishtitle = "Radio interferometric investigations of solar phenomena and
calibration method using GPS satellites",
language = "pt",
pages = "219",
ibi = "8JMKD3MGP8W/34NP558",
url = "http://urlib.net/ibi/8JMKD3MGP8W/34NP558",
targetfile = "publicacao.pdf",
urlaccessdate = "09 maio 2024"
}