@MastersThesis{Diniz:2016:HEPhNe,
author = "Diniz, Gabriel Sousa",
title = "High energy emissions from thunderstorms: HEETs, from photons to
neutrons toward the ground",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2016",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2016-03-04",
keywords = "neutrons, photons, cross sections, Monte Carlo, n{\^e}utrons,
f{\'o}tons, se{\c{c}}{\~o}es de choque.",
abstract = "Thunderstorms are the starting point of several intense phenomena
such as gamma rays and X rays, neutron, positron and electron
emissions. The X rays and gamma rays have energies that may reach
100 MeV. The neutron emissions may be created by energetic gamma
ray photons interacting with the air via Giant Dipole Resonance, a
photonuclear reaction, related to thunderstorms and lightning in a
way that is not completely understood yet. In this work neutrons
were assumed to be created by gamma ray photons in the energy
range of 10-30 MeV emitted by leader discharges. Their production
and propagation toward the ground were investigated using computer
simulations. Cross sections data banks were analyzed to provide
estimations on the neutrons creation probability. The analysis
revealed that the probability per collision of a photonuclear
occurs varies between 0 and 3.2\% through the energy range of 10
and 30 MeV. The photons mean free path within this energy range
was analyzed together with the atmospheric density profile showing
that for photon source altitudes above 1 km, the photons with this
energy pass through a sufficiently high number of mean free path
to ensure a collision. The free software EGS5 was used to treat
the photons and electrons motion through the atmosphere in the
intent of analyze the spread of the beams, that were assumed to be
monodirectional. The photon beam presented an aperture of
2-6\$^{o}\$ \$\pm\$ 2\$^{o}\$ while the electron beam was
broader showing an aperture of 11-13\$^{o}\$ \$\pm\$
3\$^{o}\$. Since EGS5 does not take into account neutron
production and motion, the neutron analysis was done with the
FLUKA software simulating a photon beam in different initial
heights and estimating the photon and neutron ground detection.
FLUKA simulations have shown that neutrons are distributed at the
ground within a radius of 2 km away from the source axis. The
neutrons reached ground with a rate of 10\$^{-4}
\$-10\$^{-2}\$ neutrons per gamma, which agrees with the cross
section analysis done upon the neutron production. The neutron
number decrease was used to estimate an upper limit of 5 km for
the altitude of a punctual photon source that is capable of
generating ground detectable neutrons. RESUMO: Nuvens de
tempestade s{\~a}o o in{\'{\i}}cio de v{\'a}rios
fen{\^o}menos intensos como os raios gama e raios X, bem como de
emiss{\~o}es de n{\^e}utrons, p{\'o}sitrons e el{\'e}trons. As
emiss{\~o}es de raios X e raios gama possuem energias que
alcan{\c{c}}am 100 MeV. As emiss{\~o}es de n{\^e}utrons podem
ser criadas por intera{\c{c}}{\~o}es entre raios gamma com o ar
atrav{\'e}s da Resson{\^a}ncia Gigante de Dipolo, uma
rea{\c{c}}{\~a}o foto-nuclear, relacionadas com as nuvens de
tempestade e com raios de um modo ainda n{\~a}o totalmente
compreendido. Neste trabalho sup{\~o}e-se que os n{\^e}utrons
s{\~a}o criados por f{\'o}tons de raios gamma com energia entre
10-30 MeV emitidos durante a propaga{\c{c}}{\~a}o do
l{\'{\i}}der negativo. A produ{\c{c}}{\~a}o e a
propaga{\c{c}}{\~a}o pelo ar destes n{\^e}utrons foram
investigadas utilizando simula{\c{c}}{\~o}es computacionais.
Bancos de dados de se{\c{c}}{\~o}es de choque foram analisados
para estimar a probabilidade por colis{\~a}o de uma
rea{\c{c}}{\~a}o foto-nuclear acontecer. A an{\'a}lise revelou
que essa probabilidade varia entre 0\% e 3.2\% para f{\'o}tons
com energia entre 10 e 30 MeV. O livre caminho m{\'e}dio dos
f{\'o}tons no intervalo de energia de 10-30 MeV foi analisado
junto com o perfil de densidade atmosf{\'e}rica. A an{\'a}lise
mostrou que para f{\'o}tons com altitude inicial acima de 1 km,
eles passam por livres caminhos m{\'e}dios o suficiente para a
probabilidade de ocorr{\^e}ncia de ao menos uma colis{\~a}o ser
garantida. O software livre EGS5 baseado no m{\'e}todo Monte
Carlo foi usado para tratar o movimento dos f{\'o}tons e
el{\'e}trons pela atmosfera no intuito de estudar a difus{\~a}o
de feixes monodirecionais dessas part{\'{\i}}culas. Foi
observado que o feixe de f{\'o}tons possui uma abertura entre
2-6\$^{o}\$ \$\pm\$ 2\$^{o}\$ enquanto o feixe de
el{\'e}trons possui uma abertura de 11-13\$^{o}\$ \$\pm\$
3\$^{o}\$ . A an{\'a}lise de n{\^e}utrons foi feita com o
software FLUKA simulando um feixe de f{\'o}tons em diferentes
altitudes iniciais e estimando a detec{\c{c}}{\~a}o de
f{\'o}tons e n{\^e}utrons no solo. As simula{\c{c}}{\~o}es do
FLUKA mostraram que os n{\^e}utrons se distribuem no solo em uma
dist{\^a}ncia radial da fonte de 2 km, chegando ao solo numa
raz{\~a}o entre 10\$^{-4}\$ at{\'e} 10\$^{-2}\$
n{\^e}utrons/f{\'o}tons, o que concorda com a an{\'a}lise das
se{\c{c}}{\~o}es de choque. A diminui{\c{c}}{\~a}o dos
n{\^e}utrons detectados em solo permitiu a estimativa de uma
altura limite de 5 km para uma fonte pontual de f{\'o}tons capaz
de produzir n{\^e}utrons detect{\'a}veis em solo.",
committee = "Alves, Maria Virginia (presidente) and Tavares, Fernanda de
S{\~a}o Sabbas (orientadora) and Ebert, Ute Maria (orientadora)
and Costa, Joaquim Eduardo Rezende and Federico, Claudio Antonio",
copyholder = "SID/SCD",
englishtitle = "Emiss{\~o}es de alta energia provindas de nuvens de tempestade.
HEETs: de f{\'o}tons para n{\^e}utrons ao solo.",
language = "en",
pages = "127",
ibi = "8JMKD3MGP3W34P/3L56P52",
url = "http://urlib.net/ibi/8JMKD3MGP3W34P/3L56P52",
targetfile = "publicacao.pdf",
urlaccessdate = "16 jun. 2024"
}