@MastersThesis{Medeiros:2021:EsPrFí,
author = "Medeiros, Daniele da Silva Ferreira",
title = "Estudo dos processos f{\'{\i}}sicos de rel{\^a}mpagos com a
utiliza{\c{c}}{\~a}o de imagens em 3D",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2021",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2020-11-06",
keywords = "rel{\^a}mpagos, raios-X, para-raios, reconstru{\c{c}}{\~a}o do
canal em 3D, velocidade m{\'e}dia em 2D e 3D, lightning, X-rays,
lightning rod, 3D channel reconstruction, 2D and 3D averege
speed.",
abstract = "Este trabalho consiste no estudo de alguns fen{\^o}menos
f{\'{\i}}sicos envolvidos durante a ocorr{\^e}ncia de
rel{\^a}mpagos, a partir da reconstru{\c{c}}{\~a}o
tridimensional do canal do rel{\^a}mpago descendente, com o
aux{\'{\i}}lio da modelagem computacional. As an{\'a}lises aqui
realizadas, foram baseadas nos dados e imagens registradas durante
as campanhas dos ver{\~o}es de 2017 a 2020. Depois de uma
an{\'a}lise detalhada do banco de dados, dois eventos se
mostraram compat{\'{\i}}veis com o tipo de estudo pretendido.
Eles ocorreram na cidade de S{\~a}o Paulo, o primeiro no dia 20
de mar{\c{c}}o de 2018, e o segundo, 16 de dezembro de 2018. No
primeiro evento, foi poss{\'{\i}}vel verificar o in{\'{\i}}cio
de um L{\'{\i}}der Ascendente N{\~a}o Conectivo (LANC) partindo
do para-raios de um pr{\'e}dio durante a aproxima{\c{c}}{\~a}o
de um l{\'{\i}}der de um rel{\^a}mpago descendente. A
reconstru{\c{c}}{\~a}o permitiu pela primeira vez no mundo
identificar a real dist{\^a}ncia de atra{\c{c}}{\~a}o
necess{\'a}ria para o para-raios iniciar um LANC durante a
propaga{\c{c}}{\~a}o de um l{\'{\i}}der. Al{\'e}m disso, foi
poss{\'{\i}}vel verificar a precis{\~a}o do m{\'e}todo
utilizado para a reconstru{\c{c}}{\~a}o em 3D. Atrav{\'e}s do
conhecimento do seu ponto de impacto no solo, obtido a partir da
an{\'a}lise dos danos causados {\`a}s moradias pr{\'o}ximas,
encontramos um erro de aproximadamente 13 metros entre o local
real de impacto e o previsto pelo m{\'e}todo. O segundo evento de
rel{\^a}mpago descendente observado e reconstru{\'{\i}}do pelo
m{\'e}todo, foi de um rel{\^a}mpago descendente que provocou a
emiss{\~a}o de raios-X. Neste trabalho foi poss{\'{\i}}vel
apresentar a dist{\^a}ncia que o l{\'{\i}}der se encontrava do
sensor de raios-X e mostrar, atrav{\'e}s da
reconstru{\c{c}}{\~a}o do canal, que o l{\'{\i}}der se
propagou por um per{\'{\i}}odo de tempo em dire{\c{c}}{\~a}o
ao sensor, o que confirma uma hip{\'o}tese de que o
l{\'{\i}}der produz raios-X de forma colimada e alinhada com a
sua propaga{\c{c}}{\~a}o. Al{\'e}m disso, este trabalho
apresenta uma nova hip{\'o}tese, a de que uma mudan{\c{c}}a
abrupta na dire{\c{c}}{\~a}o de propaga{\c{c}}{\~a}o do
l{\'{\i}}der do canal, gera uma acelera{\c{c}}{\~a}o que pode
ser respons{\'a}vel pela emiss{\~a}o de raios-X. Para validar o
m{\'e}todo no segundo evento, utilizamos o tempo de
propaga{\c{c}}{\~a}o do trov{\~a}o para calcular a menor
dist{\^a}ncia do l{\'{\i}}der ao sensor de raios-X. Novamente,
o erro do algoritmo de reconstru{\c{c}}{\~a}o se mostrou
pequeno. Tamb{\'e}m analisamos a velocidade de
propaga{\c{c}}{\~a}o de rel{\^a}mpagos 2D e 3D para os dois
eventos estudados. ABSTRACT: This work consists of studying some
physical phenomena involved during lightning strikes, with the aid
of computational modeling for the three-dimensional reconstruction
of the lightning channel. The analyzes performed here were based
on the data and images produced during the summer campaigns from
2017 to 2020. After a detailed analysis of the database, two
events were defined with the type of study intended. They took
place in the city of S{\~a}o Paulo, the first on March 20, 2018,
and the second, December 16, 2018. In the first event, it was
possible to verify the beginning of a Unconnected Upward
Connecting Leader (UUCL) starting from the lightning rod of a
building during the approach of a downward lightning leader. For
the first time in the world, the reconstruction made it possible
to identify the real distance of attraction necessary for the
arresters to initiate a UUCL during the propagation of a leader.
Besides, it was possible to verify the accuracy of the method used
for 3D reconstruction. Through the knowledge of its point of
impact on the ground, obtained from the analysis of the damage
caused to the nearby houses, an error of approximately 13 meters
between the real impact site and the one predicted by the method
was found. The second event observed and reconstructed by the
method was a downward lightning that caused the emission of
X-rays. In this work, it was possible to present the distance the
leader was from the X-ray sensor. The reconstruction of the
channel shows that the leader propagated for a while towards the
sensor, which confirms the hypothesis that the leader produces
X-rays in a collimated manner and aligned with their spread.
Further, this work presents a new hypothesis, that an abrupt
change in the direction of propagation of the channel leader
generates an acceleration that may be responsible for the emission
of X-rays. To validate the method in the second event, the
propagation time of the thunder was used to calculate the shortest
distance from the leader to the X-ray sensor. Again, the error of
the reconstruction algorithm turned out to be small. We also
analyzed the propagation speed of 2D and 3D lightning for the two
events studied.",
committee = "Alves, Maria Virginia (presidente) and Saba, Marcelo
Magalh{\~a}es Fares (orientador) and Saraiva, Antonio Carlos
Varela (orientador) and Naccarato, Kleber Pinheiro and Paiva,
Amanda Rom{\~a}o de and Ballarotti, Mauricio Grade",
englishtitle = "Study of the physical processes of lightning applying 3D images",
language = "pt",
pages = "110",
ibi = "8JMKD3MGP3W34R/43LUJT2",
url = "http://urlib.net/ibi/8JMKD3MGP3W34R/43LUJT2",
targetfile = "publicacao.pdf",
urlaccessdate = "04 maio 2024"
}