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@PhDThesis{Sim˘esJr:2008:SiCoEm,
               author = "Sim{\^o}es Junior, Fernando Jaques Ruiz",
                title = "Simula{\c{c}}{\~a}o computacional de emiss{\~o}es 
                         eletromagn{\'e}ticas em plasmas espaciais",
               school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
                 year = "2008",
              address = "S{\~a}o Jos{\'e} dos Campos",
                month = "2008-06-06",
             keywords = "plasma, instabilidade, clima espacial, ondas de plasma, 
                         simula{\c{c}}{\~a}o, plasma, instabilities, space weather, 
                         plasma waves, computer simulation.",
             abstract = "Atualmente sabemos que feixes de el{\'e}trons desempenham um 
                         importante papel no mecanismo de emiss{\~o}es de r{\'a}dio que 
                         s{\~a}o comumente observadas na regi{\~a}o acima do arco de 
                         choque terrestre e explos{\~o}es solares tipo II e III. Feixes de 
                         el{\'e}trons que s{\~a}o injetados de volta no vento solar, a 
                         partir do arco de choque terrestre, s{\~a}o uma poss{\'{\i}}vel 
                         fonte das ondas de plasma observadas pelos sat{\'e}lites nesta 
                         regi{\~a}o. Pesquisas recentes sugerem que m{\'u}ltiplos feixes 
                         de el{\'e}trons podem ser injetados em um determinado 
                         per{\'{\i}}odo de tempo. Estes m{\'u}ltiplos feixes tendem a 
                         perder suas identidades individuais para formar um {\'u}nico 
                         feixe. No arco de choque terrestre, observa{\c{c}}{\~o}es 
                         t{\^e}m mostrado que part{\'{\i}}culas energ{\'e}ticas possuem 
                         algum grau de organiza{\c{c}}{\~a}o na fase de giro. Isto 
                         {\'e}, a distribui{\c{c}}{\~a}o de velocidades das 
                         part{\'{\i}}culas no plano perpendicular ao campo magn{\'e}tico 
                         ambiente depende do {\^a}ngulo de giro das part{\'{\i}}culas. 
                         Na primeira parte deste trabalho, resolvemos numericamente a 
                         rela{\c{c}}{\~a}o de dispers{\~a}o n{\~a}o girotr{\'o}pica 
                         utilizando par{\^a}metros de plasma baseados em medidas 
                         observacionais que mostram o agrupamento de fase dos el{\'e}trons 
                         acima do arco de choque terrestre. A import{\^a}ncia da n{\~a}o 
                         girotropia na fun{\c{c}}{\~a}o de distribui{\c{c}}{\~a}o 
                         n{\~a}o est{\'a} completamente compreendida. Para antecipar o 
                         comportamento n{\~a}o girotr{\'o}pico, resolvemos numericamente 
                         a rela{\c{c}}{\~a}o de dispers{\~a}o girotr{\'o}pica paralela 
                         que mostra as poss{\'{\i}}veis regi{\~o}es de acoplamento 
                         quando a n{\~a}o girotropia {\'e} introduzida. Encontramos que a 
                         n{\~a}o girotropia pode fazer o acoplamento dos modos mesmo 
                         quando o sistema {\'e} isotr{\'o}pico. Para uma determinada 
                         n{\~a}o girotropia, a taxa de crescimento apresenta 
                         depend{\^e}ncia na raz{\~a}o entre as freq{\"u}{\^e}ncias de 
                         plasma e ciclotr{\^o}nica, bem como na anisotropia da 
                         temperatura, conhecida como um importante fator na 
                         determina{\c{c}}{\~a}o das instabilidades. Na segunda parte 
                         deste trabalho utilizamos um c{\'o}digo de part{\'{\i}}culas 
                         eletromagn{\'e}tico (KEMPO 1D modificado) para simular dois 
                         feixes de el{\'e}trons que s{\~a}o injetados no plasma em 
                         diferentes instantes de tempo. O primeiro feixe perturba o plasma 
                         ambiente introduzindo ondas de Langmuir atrav{\'e}s de 
                         intera{\c{c}}{\~a}o feixe de plasma. Em seguida, o outro feixe 
                         {\'e} injetado no sistema e interage com o primeiro e com as 
                         ondas de Langmuir para produzir radia{\c{c}}{\~a}o 
                         eletromagn{\'e}tica. As condi{\c{c}}{\~o}es iniciais para os 
                         feixes de el{\'e}trons e para o plasma ambiente s{\~a}o baseadas 
                         em observa{\c{c}}{\~o}es do vento solar e regi{\~a}o do 
                         antechoque terrestre. Em nosso modelo, consideramos que o primeiro 
                         e o segundo feixe de el{\'e}trons, em \$ t=0\$ , ocupam todo o 
                         sistema; isto {\'e} necess{\'a}rio para evitar efeitos 
                         num{\'e}ricos nas grades de contorno e permitir a possibilidade 
                         de utilizarmos o modelo mais simples. Os resultados mostraram que 
                         o primeiro feixe pode produzir harm{\^o}nicos da 
                         freq{\"u}{\^e}ncia de plasma e o segundo feixe modifica a 
                         emiss{\~a}o dos harm{\^o}nicos gerados pelo primeiro feixe. O 
                         segundo feixe de el{\'e}trons interage rapidamente com o intenso 
                         campo el{\'e}trico das ondas de Langmuir fazendo o acoplamento de 
                         fase com o primeiro feixe. Um aumento da energia das componentes 
                         eletromagn{\'e}ticas e da energia cin{\'e}tica tamb{\'e}m 
                         {\'e} observado. ABSTRACT: It is by now well known that electron 
                         beams play an important role in generating radio emissions such as 
                         commonly observed by spacecraft upstream of the Earth's bow shock 
                         and type II and III radio bursts. Electron beams streaming back 
                         from Earth's bow shock into the solar wind have been proposed as a 
                         possible source for the electron plasma waves observed by 
                         spacecraft in the electron foreshock. Recent researche suggest 
                         that multiple electron beams could be injected over a period of 
                         time. They tend to lose their individual identity to form just a 
                         single beam. In Earth's Bow Shock, particle observations have 
                         shown that high energy particles have some degree of gyrophase 
                         organization. Namely, the velocity distribution of the particle 
                         populations in the plane perpendicular to the ambient magnetic 
                         field depends on the gyrophase angle. In the first part of this 
                         work we solve numerically the nongyrotropic parallel dispersion 
                         relation using plasma parameters based on observational data that 
                         show a component of phase-bunched electrons upstream from the 
                         Earth's bow shock. The importance of nongyrotropic electron 
                         distribution in the upstream of the Earth's bow shock is not fully 
                         understood. To anticipate the nongyrotropic behavior, we solve 
                         numerically the gyrotropic parallel dispersion equation that shows 
                         the potential regions of strong coupling when the electron 
                         nongyrotropy is introduced. We find that the nongyrotropy can lead 
                         to a coupling between modes even when the temperature anisotropy 
                         is equal to 1. For a given nongyrotropic angle, the growth rate 
                         presents a dependence on the ratio between electron cyclotron and 
                         electron plasma frequencies as well as on the temperature 
                         anisotropy, known as an important player on determining the growth 
                         rates and the regions were instabilities occur. In the second part 
                         of this thesis we use an electromagnetic PIC code (KEMPO 1D, 
                         modified) to simulate two beams which are injected into a plasma 
                         at different times. The first beam disturbs the background plasma 
                         and generates Langmuir waves by electron beam-plasma interaction. 
                         Subsequently, another beam is inserted in the system and interacts 
                         with the first one and with the Langmuir waves to produce 
                         electromagnetic radiation. The initial conditions for the 
                         background plasma and the electron beams are based on the solar 
                         wind and electron foreshock observations. In our model we consider 
                         that the first and the second beams (for simple and multiples 
                         injections) are, at t=0, fully injected into the system, i.e., the 
                         beam occupies all the system; this is necessary to avoid grid 
                         effects at the boundaries and gives the possibility of using a 
                         simpler model. The results of our simulation show that the first 
                         beam can produce electrostatic harmonics of plasma frequency while 
                         the second beam modifier the harmonics emission that are produced 
                         by the first one. The second beam interacts very fast with the 
                         Langmuir waves due to the strong electric field and the phase 
                         coupling with the first beam. An increasing of electromagnetic and 
                         kinetic energies is also observed.",
            committee = "Souza, Jonas Rodrigues de (presidente) and Alves, Maria 
                         Virg{\'{\i}}nia (orientadora) and Bittencourt, Jos{\'e} Augusto 
                         and Dutra, Severino Luiz Guimar{\~a}es and Gaelzer, Rudi",
           copyholder = "SID/SCD",
         englishtitle = "Computational simulation of electromagnetic emission in space 
                         plasmas",
             language = "pt",
                pages = "163",
                  ibi = "6qtX3pFwXQZGivnK2Y/TQSv8",
                  url = "http://urlib.net/rep/6qtX3pFwXQZGivnK2Y/TQSv8",
           targetfile = "publicacao.pdf",
        urlaccessdate = "21 jan. 2021"
}


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