AMS-02 est un spectromètre magnétique conçu pour la détection du rayonnement cosmique chargé et des photons gamma. La mesure en 2013 de la fraction de positons par AMS-02 a confirmé la présence d'une composante de positons primaires, nécessitant l'existence d'une source de positons dans notre Galaxie. Cette thèse s'est exclusivement consacrée à l'étude de ce phénomène, et à la recherche de cette source de positons. La fraction de positons, le flux de positons et le flux d'électrons sont mesurés à l'aide d'une méthode de fit multidimensionnel mis au point lors de cette thèse. Une étude particulière est réservé au phénomène de confusion de charge, important pour la mesure du signe de la charge à haute énergie. La fonction de réponse instrumentale du détecteur est évaluée à l'aide de simulations Monte Carlo et est corrigée par les données réelles du détecteur. Un travail phénoménologique est effectué afin d'interpréter les résultats mesurés. L'interprétation de ces résultats en termes de composante primaire issues d'un pulsar local et du halo galactique de matière noire est effectué. Les implications et l'espace des paramètres autorisé pour chacun des modèles est explicité. Une ré-évaluation des secondaires à l'aide des nouvelles données d'AMS-02, ainsi que l'étude de l'impact de l'erreur expérimentale d'AMS-02 sur ces résultats, est exécuté. / AMS-02 is a magnetic spectrometer design for the cosmic ray and gamma ray detection. The measurement in 2013 of the positron fraction by AMS-02 confirmed the presence of a primary positron component, which means the existence of a galactic primary source of positrons. This thesis is devoted exclusively to the study of this phenomenon. The positron fraction, the positron flux, and the electron flux are measured using a method of multidimensional fit developed during this thesis. The charge confusion phenomenon, which is important at the highest energies, is investigated. The instrumental response function of the detector is evaluated using Monte Carlo simulations and is corrected using the ISS data. A phenomenological work is done to interpret the measured results. The interpretation of these results in terms of primary component from a local pulsar and dark matter halo is done. The implications and the parameter space allowed for each model is detailed. A reevaluation of secondaries with the new AMS-02 data, and the study of the impact of the experimental error of AMS-02 on these results is performed.

Recentemente, o Observatório Pierre Auger tem medido espectro de energia de Raios Cósmicos Ultra Energéticos (Ultra High Energy Cosmic Rays - UHECR) (E > 1019 eV) com grande acurácia. No entanto, o estudo de raios cósmicos ultra energéticos na Terra tem uma forte dependência do estudo de sua propagação no Universo. Neste trabalho, abordamos o estudo da propagação de raios cósmicos em diferentes aspectos. Núcleos em alta energia interagem com os campos de radiação no caminho da fonte à Terra. A interação mais importante é a fotodesintegração. Na primeira parte, implementamos de maneira analítica e numérica a solução da razão de fotodesintegração e fizemos uso da solução numérica em um programa de Monte Carlo. Mostramos soluções baseadas na parametrização das seções de choque por uma função Gaussiana e por uma função Lorenztiana. Comparamos nossos resultados com trabalhos prévios da literatura. O seguinte estudo mostrou que sob a hipótese de propagação quase-linear e utilizando várias distribuições de fontes no céu, a latitude do observatório: tem influência no fluxo total medido por um observatório; impõe um limite na capacidade de medida de anisotropia e tem um efeito negligenciável na medida do XMax. No terceiro estudo, um limite superior na integral do fluxo de raios gama em GeV-TeV é usado para obter um limite superior na luminosidade total de UHECR de fontes individuais. A correlação entre o limite superior na integral do fluxo de raios gama e o limite superior na luminosidade total de UHECR é estabelecida através do processo de cascatas de partículas geradas durante a propagação de raios cósmicos nos campos de radiação. / Recently, the Pierre Auger Observatory has measured the energy spectrum of Ultra High Energy Cosmic Rays (UHECR) (E > 1019 eV) with an unprecedented accuracy. However, the study of ultra-high energy cosmic rays at Earth depends on the models used to describe the propagation of the particle in the Universe. In this work, we present a study of propagation of cosmic rays on different aspects. Nucleus at this high energy interacts with the radiation fields on the way from the source to Earth. The most important interaction is the photodisintegration. In the first part, we implemented analytical, numerical and Monte Carlo simulation solutions for the photodisintegration rate. We show solutions based on parameterizations of the cross-section using Gaussian and Lorenztian functions. We compare our results with previous works. The following study shows that under the assumption of quasi-linear propagation and using several sources distributions of sky, the latitude of the observatory: has influence on the total flux measured by an observatory; imposes a limitation on the capability of measuring an anisotropic sky and has a negligible efect on the Xmax measurement. In the thirdy study, an upper limit on the integral flux of GeV-TeV gamma-rays is used to extract the upper limit on the total UHECR luminosity of individual sources. The correlation between upper limit on the integral GeV-TeV gamma-rays flux and upper limit on the UHECR luminosity is established through the cascading process that takes place during propagation of the cosmic-rays in the background radiation fields.

Orientador: Jose Augusto Chinellato / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-09T22:35:29Z (GMT). No. of bitstreams: 1 Perassa_EderArnedo_M.pdf: 7742499 bytes, checksum: 5f8e2630e2b11b5f5965e6b95c19be9b (MD5) Previous issue date: 2007 / Resumo: Neste trabalho são estudados os métodos de estatística bayesiana e máxima entropia na análise de dados. É feita uma revisão dos conceitos básicos e procedimentos que podem ser usados para in-ferência de distribuições de probabilidade. Os métodos são aplicados em algumas áreas de interesse, com especial atenção para os casos em que há pouca informação sobre o conjunto de dados. São apresentados algoritmos para a aplicação de tais métodos, bem como alguns exemplos detalhados em que espera-se servirem de auxílio aos interessados em aplicações em casos mais comuns de análise de dados / Abstract: In this work, we study the methods of Bayesian Statistics and Maximum Entropy in data analysis. We present a review of basic concepts and procedures that can be used for inference of probability distributions. The methods are applied in some interesting fields, with special attention to the cases where there¿s few information on set of data, which can be found in physics experiments such as high energies physics, astrophysics, among others. Algorithms are presented for the implementation of such methods, as well as some detailed examples where it is expected to help interested in applications in most common cases of data analysis / Mestrado / Física das Particulas Elementares e Campos / Mestre em Física

Orientador: Carlos Ourivio Escobar / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-11T18:57:31Z (GMT). No. of bitstreams: 1 Peixoto_CarlosJoseTodero_D.pdf: 15351567 bytes, checksum: 33b4f282f53a5669d23f8170b3bbf392 (MD5) Previous issue date: 2008 / Resumo: Desde os primeiros Raios Cósmicos de alta energia detectados por Pierre Auger na década de 30, toda a comunidade de Física de Radiação Cósmica procura técnicas matemáticas e métodos estatísticos mais adequados para analisar estes eventos. Estes processos de análise são imprescindíveis na estimativa da energia da partícula primária, bem como no cálculo do ângulo de chegada q . A estimativa desta energia e do ângulo q é o final de toda uma rede de trabalho e o começo de uma nova linha de pesquisa na busca pelas possíveis fontes que produziram tais eventos. Ao longo deste trabalho refizemos o princípio de reconstrução dos "chuveiros de Auger", os chamados "Chuveiros Atmosféricos Extensos" ( C.A.E.), utilizando um conceito relativamente novo de estatística, hoje denominada Estatística Robusta. O Método dos Mínimos Quadrados ou Least Square -LS, apresentado por Gauss e Legendre, possuía limitações que eles próprios já reconheciam e tentaram resolver, sem sucesso. Desde fins do século XVIII e come¸ co do século XIX, os métodos estritamente paramétricos, em especial o Método dos Mínimos Quadrados e a média aritmética, foram questionados quando utilizados para descrever distribuições pouco comportadas ou com grandes utuações. Algumas das principais questões estavam relacionadas a como tratar pontos muito distantes da distribuição principal (os chamados outliers) e como estes influenciavam a própria distribuição. A saída convencional mais utilizada foi a rejeição dos outliers e de pontos que apresentassem grandes desvios em relação a média. Porém, a perda de informações sobre a própria distribuição tornava-se inevitável. O modelo paramétrico mostrou-se apenas uma aproximação da realidade, uma vez que as flutuações, apesar de serem consideradas, não são "bem-vindas"; são vistas apenas como um erro inerente à observação. Então, no fim do século XIX apareceram as primeiras tentativas de extrair informação das flutuações, classificando-as e as considerando parte integral da descrição da distribuição. Se um método estatístico for capaz de descrever os dados observados, incluindo e classificando as flutuações inerentes, este passa a ser conhecido como "Método Robusto" ou "Estatística Robusta", onde a nomenclatura "Robusta" está relacionada à capacidade do método ou modelo de "resistir" às flutuações fornecendo uma descrição da realidade com razoável independência destas mesmas flutuações. Com base em dois métodos robustos, Mínima Mediana Quadrada (Least Median Square - LMS) e Mínimos Quadrados "Aparados" (Least Trimmed Square - LTS), aplicamos estes nos ajustes da Função Distribuição Lateral de Chuveiros (Lateral Distribution Function - LDF) extraindo o valor de S 1000, parâmetro necessário para estimar a energia da partícula primária. Os valores para S1000 calculados a partir de estatística convencional (Mínimos Quadrados) e estatística robusta (LMS e LTS) são comparados. O valor de S1000, para chuveiros de mesma energia, depende do ângulo q dos primários, já que o CAE sofre atenuação na atmosfera, atenuação esta tanto maior quanto maior, for q . Para levar em conta a atenuação no cálculo do espectro de energia, em que todos os ângulos de chegada são considerados (até 60 graus), é introduzido o parâmetro S38, onde 38 graus é a mediana dos dados do Auger. A atenuação é calculada usando-se o método do Constant Intensity Cut (CIC) o qual depende da validade de várias hipóteses. As três hipóteses supostas pela Colaboração Auger são apresentadas neste trabalho. Correlacionamos, assim, todos os novos valores de S38 com os valores da chamada "Energia Híbrida", obtida diretamente do programa de análise da Colaboração Auger. Esta correlação nos permite recorrigir a energia com base em detecção híbrida, que é a grande vantagem do Observatório Pierre Auger. Esta correlação nos permite estabelecer a escala de energia ou calibração do detector de superfície com base na determinação calorimétrica da energia feita pelo detector de flurescência, que é o grande avançoo trazido para o campo pelo Obvservatório Pierre Auger. Com os novos resultados de energia, refizemos os cálculos de minimização para a correlação de radiação cósmica com fontes extra-galácticas obtendo correlações que não estão em correspondência biunívoca com aquelas obtidas pelo método convencional de análise. Por fim fazemos uma análise das próprias estações outliers tentando extrair alguma informação relacionada à performance do detector de superfície. Os apêndices incluídos após as conclusões foram colocados neste trabalho apenas por motivos didáticos como consulta rápida para o leitor leigo em métodos de detecção de radiação cósmica / Abstract: Since the first ultra high-energy cosmic rays detected by Pierre Auger (the 30s) the entire community of Physics of Cosmic Rays search for mathematical techniques and more appropriate statistical methods to analyze these events. These analysis processes are essential for the estimate of the energy of the primary particle as well as in the calculation of the angle of arrival q . The estimate of the energy and the angle q is the end of a long chain of analysis and the beginning of a new line of research in the search for the possible sources that produced such events. Throughout this work we re-analysed the reconstruction chain of the "Auger showers", the socalled "Extensive Air Showers - EAS", using a relatively new concept of statistics, known as Robust Statistics. The Least Square Method - LS, presented by Gauss and Legendre had limitations already recognized by themselves who tried to overcome them without success. Since the end of the eighteenth century and beginning of the nineteenth century, strictly parametric methods, especially the Least Squares and the arithmetic average, were questioned when used to describe distributions with bad behavior or with large uctuations. Some of the main issues were related to how to deal with points far way from the main distribution (the so-called outliers) and how it in uenced the main distribution. The more conventional way out used was the rejection of the outliers and points that produced large deviations from average. But the loss of information about the distribution was inevitable. The parametric model proved to be only an approximation of reality, since uctuations, despite being considered, are not "welcome"; are seen only as an error inherent in observation. Then, at the end of the nineteenth century there appeared the first attempts to extract information from uctuations sorting them out and considering them as an integral part of the description of the distribution. Whether a statistical method is able to describe observed data, including and sorting the uctuations inherent, then becomes known as "Robust Method" or "Robust Statistic", where the nomenclature "Robust" is related the ability of the method or model to "Resist" the uctuations by providing a description of reality with reasonable independence these same uctuations. Based on two robust methods: Least Median Square - LMS and Least Trimmed Square - LTS; we apply these to adjust the Lateral Distribution Function - LDF extracting the value of S1000, parameter needed to estimate the energy of the primary particle. The values for S1000 calculated from conventional statistic (Least Square) and robust statistic (LMS and LTS) are compared. The parameter S1000 is dependent on the angle of arrival of the shower, then we apply a correction factor called S38. This correlates S1000 and and, currently, there are several ways to calculate this factor. The three hypotheses most used by Auger Collaboration are presented in this work. We then correlate all new values of S38 with the values of the so-called "Hybrid Energy", obtained directly from analysis software of the Auger Collaboration. This relationship allows us to correct the energy based on hybrid detection that is great advantage of the Pierre Auger Observatory. This relationship allows us to establish the energy scale or calibration of the surface detector on the basis of the calorimetric determination of the energy done by the uorescence detector which is the great advancement brought to the field by the Pierre Auger Observatory. With the new results for the energy we reanalysed the the correlation with extra-galactic sources of cosmic ray getting new correlations, which are absent in the conventional methods of analysis. Finally we make an analysis of the surface stations outliers by themselves trying to extract some information relevant for their performance. Appendices included after the conclusions were placed in this work only for a rapid consultation by lay readers in methods of detection of cosmic rays / Doutorado / Teorias Especificas e Modelos de Interação ; Sistematica de Particulas ; Raios Cosmicos / Doutor em Ciências

Orientador: Ernesto Kemp / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-20T15:39:35Z (GMT). No. of bitstreams: 1 Batista_RafaelAlves_M.pdf: 8040703 bytes, checksum: 596e886c4828986af7fb003ba71adf9b (MD5) Previous issue date: 2012 / Resumo: Campos magnéticos cósmicos são ubíquos e estão presentes em todas as escalas, desde os planetas até os superaglomerados de galáxias. Sabe-se que o campo magnético da Via Láctea possui uma componente regular, que tem uma estrutura espiral, e uma componente aleatória. Muitas questões acerca do magnetismo galáctico ainda permanecem sem respostas, e o modelo de espiral mais adequado para descrever as observações é incógnito. Uma possibilidade pouco explorada para estudar o campo magnético da Via Láctea é utilização de informações relacionadas à propagação de partículas carregadas através da mesma. Neste contexto estão inseridos os raios cósmicos ultra-energéticos, as partículas mais energéticas do universo, cuja origem, composição química e mecanismos de aceleração e propagação não são bem compreendidos. A deflexão de partículas provenientes da mesma fonte no campo magnético galáctico pode gerar estruturas filamentares com eventos ordenados por energia, os chamados multipletos, sendo esta uma assinatura única deixada pelo campo em mapas contendo direções de chegada de raios cósmicos. Neste trabalho é apresentado um método inédito para estudos do campo magnético galáctico, através da identificação e análise da orientação de multipletos nestes mapas. Este método baseia-se na transformada de wavelets na esfera, que permite amplificar a razão sinal-ruído e fazer reconhecimento de padrões, de forma a identificar multipletos imersos em ruído de natureza estocástica. Na primeira parte do trabalho o método foi aplicado a dados simulados visando obter a orientação esperada para multipletos oriundos de fontes em diversas partes da esfera celeste, segundo diferentes modelos de campo magnético galáctico. Na segunda parte do trabalho, aplicou-se o método a eventos detectados pelo Observatório de Raios Cósmicos Pierre Auger. A confrontação dos resultados de dados reais e simulações permite restringir modelos de campo magnético galáctico / Abstract: Cosmic magnetic fields are ubiquitous and are present in all size scales, from planets to superclusters of galaxies. The magnetic field of the Milky Way has a regular component, with a spiral structure, and a random component. Many questions concerning galactic magnetism still remain unanswered, and the spiral model which best fits the observations is unknown. An underexplored possibility to probe these fields is to use information related to the propagation of charged particles through them. In this context, an interesting probe are the ultrahigh energy cosmic rays, the most energetic particles in the universe, whose origin, chemical composition and mechanisms of acceleration and propagation are not well-understood. The deflection of particles coming from the same source can generate threadlike structures with events ordered by energy, the so-called multiplets, which imprints a unique signature of the galactic magnetic field in maps containing arrival directions of cosmic rays. In the present work it is presented a novel method to probe the galactic magnetic field, by identifying and analysing the orientation of multiplets in these maps. This method relies on the spherical wavelet transform, which is capable of amplifying the signal-to-noise ratio and perform pattern matching, so that it is possible to identify multiplets embedded in a stochastic background. In the first part of this work the method is applied to simulated data, aiming to obtain the expected orientations for multiplets associated to sources in several regions of the celestial sphere, according to different models of galactic magnetic field. In the second part of the work the method was applied to events detected by the Pierre Auger Observatory. A confrontation between the results using real and simulated data allows one to impose constraints to galactic magnetic field models / Mestrado / Física / Mestre em Física

Les rayons cosmiques ont été découverts il y a un siècle par Victor Hess à bord d'un vol scientifique en ballon. La physique des rayons cosmiques et les ballons stratosphériques ont partagé depuis lors une histoire commune, que ce soit pour d'authentiques découvertes ou en utilisant les ballons comme plateformes de test technologique pour de nouvelles missions satellites. Cette thèse, développée au sein de la collaboration JEM-EUSO, traite d'un démonstrateur en ballon stratosphérique. Notre but scientifique final est l'étude des Rayons Cosmiques de Ultra-Haute Energie (RCUHE), les particules les plus énergétiques connues dans l'Univers. Les RCUHES ont des énergies macroscopiques de plus de 10^20eV mais étant extrêmement rares, leurs origines sont encore inconnues. Ces derniers pénètrent notre atmosphère à une fréquence de un par km2 par siècle, produisant une gerbe atmosphérique géante, détectable notamment par la lumière de fluorescence ultraviolette qu'elle émet. Le principe de détection proposé par notre collaboration consiste dans l'utilisation d'un observatoire spatial, JEM-EUSO. Son objectif est d'observer un très grand volume d'atmosphère afin d'enregistrer un nombre significatif des événements ultra-violet de fluorescence initiés par les RCUHEs. Le démonstrateur EUSO-Ballon a été développé par la collaboration JEM-EUSO dans le but de démontrer les technologies et méthodes utilisées par le futur instrument spatial. Le 25 août 2014, EUSO-Ballon a été lâché depuis la base de ballons stratosphériques de Timmins (Ontario, Canada) par la division ballon du CNES. L'instrument a fonctionné pendant toute une nuit astronomique, observant depuis 38km d'altitude la lumière UV provenant de divers types de sols et de centaines de gerbes atmosphériques simulées. Ces dernières ont été produites par des flashers et un laser embarqués dans un hélicoptère volant sous EUSO-Ballon pendant deux heures. Ces résultats ont été rendus possibles par la restitution de l'attitude de l'instrument effectuée à l'IRAP, c'est-à-dire une analyse exhaustive des données du vol des différents appareils de mesure d'attitude de la nacelle du ballon. Une caractérisation précise de chaque sous-système était aussi indispensable à l'exploitation des données du vol. Le système optique innovant, composé de deux grandes lentilles de Fresnel, a été intégré et entièrement testé à l'IRAP. Face au large système réfractif de l'instrument, une nouvelle méthodologie de test a été développée. Les performances de l'optique, efficacité et spot focal, ont ainsi été mesurées et se sont révélées étonnamment différentes des prédictions des modèles numériques. Ces mesures sont utilisées pour l'analyse des données du premier vol et pour mieux comprendre le comportement de ces toutes nouvelles optiques, éléments clés dans la conception de l'instrument JEM-EUSO. / A century ago Cosmic Rays were discovered by Victor Hess during one of the very first scientific balloon flights. Ever since, Cosmic Ray physics and stratospheric balloons have shared a common history - either through genuine discoveries or by using balloon platforms as technology test beds for new satellite missions. This thesis, carried out within the JEM-EUSO collaboration, is about such a pathfinder balloon mission. Our ultimate science goal is the study of Ultra-High Energy Cosmic Rays (UHECR), the most energetic particles known in the Universe. Having macroscopic energies of over 10^20 eV, UHECRs are of yet unknown cosmic origin and are extremely rare. They penetrate our atmosphere at a rate of about one event per km2 and century, producing energetic atmospheric air showers, detectable through the ultraviolet fluorescence light they emit. The technique that our collaboration proposes for their detection consists of a spaceborne observatory, JEM-EUSO. Its objective is to monitor a very large volume of the Earth's nighttime atmosphere from above, recording a significant sample of ultraviolet light tracks initiated by UHECRs. In order to demonstrate the technologies and methods featured in the future space instrument, the EUSO-Balloon pathfinder has been developed by the JEM-EUSO collaboration. On August 25, 2014, EUSO-Balloon was launched from Timmins Stratospheric Balloon Base (Ontario, Canada) by the balloon division of the French Space Agency CNES. From a float altitude of 38 km, the instrument operated during the entire astronomical night, observing UV-light from a variety of groundcovers and from hundreds of simulated air showers, produced by flashers and a laser during a two-hour helicopter under-flight. These results have been made possible by the restitution of the instruments attitude carried out at IRAP, i.e. an exhaustive analysis of the flight data from various attitude sensors on board of the balloon gondola. Also, a precise understanding of the Fresnel optics was required to analyze the data of the first EUSO-balloon flight. The all new optical system, integrated and tested at IRAP, has been characterized during two measurement campaigns. To test this large refractive system, a new test method has been developed. The optics performance, i.e. the efficiency and point spread function, came as something of a surprise, since none of the numerical models had predicted the observed behavior. These measurements are used in the analysis of the flight data and for the deep understanding of these brand-new Fresnel optics, key element in the design of the JEM-EUSO instrument.

Orientador: Carola Dobrigkeit Chinellato / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T01:00:42Z (GMT). No. of bitstreams: 1 Rodrigues_JoaoPauloCaminhaCascudo_M.pdf: 7322384 bytes, checksum: e50136f5ec9d16fff8fd6a15ba64b5f0 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho estuda-se a propagação pelo meio intergaláctico de raios cósmicos ultra-energéticos partindo de fontes com distribuição espacial uniforme, considerando as perdas de energia ocasionadas pela expansão adiabática do universo e pelas interações com a Radiação , Cósmica de Fundo (produção de pares e-e+ e fotoprodução de píons), o que resulta no aparecimento do corte GZK (Greisen-Zatsepin-Kuzmin). A degradação de energia no espectro primário da radiação cósmica que chega ao topo da atmosfera terrestre é então analisada para diferentes redshifts das fontes injetoras. São utilizadas simulações de Monte Carlo bem como uma abordagem analítica, com a posterior comparação dos resultados obtidos em cada método. Uma vez conhecido o fluxo propagado, é feita uma estimativa da forma da resolução de energia do Observatório Pierre Auger, com a decorrente convolução desta resolução com o fluxo propagado, novamente utilizando-se ambos os métodos. Os resultados mostram que o corte GZK pode se mostrar severamente atenuado no fluxo convoluído, o que dificulta a sua constatação experimental / Abstract: In this work, we study the propagation of Ultra-High Energy Cosmic Rays (UHECR) which are injected into the intergalactic medium by sources with flat spatial distribution for several redshifts. The energy spectrum of UHECR observed on the Earth is directly influenced by the energy losses due to both the adiabatic expansion of the universe and interactions with the Cosmic Microwave Background radiation (e-e+ pair production and photoproduction of pions), which cause the so-called Greisen-Zatsepin-Kuzmin (GZK) cutoff. We perform Monte Carlo simulations and also consider a semi-analytical approach and compare the results obtained by each method. Once the propagated primary flux is known, we make a simple estimate of the shape of the Pierre Auger Observatory energy resolution. This resolution is folded with the propagated primary flux again utilizing both methods. The results show the GZK cutoff may be severely smeared and might not be detected as sharp as predicted. / Mestrado / Teorias Especificas e Modelos de Interação ; Sistematica de Particulas ; Raios Cosmicos / Mestre em Física

The modulation of galactic cosmic ray (GCR) Carbon in a north-south asymmetrical heliosphere is studied, using a two-dimensional numerical model that contains a solar wind termination shock (TS), a heliosheath, as well as particle drifts and diffusive shock re-acceleration of GCRs. The asymmetry in the geometry of the heliosphere is incorporated in the model by assuming a significant dependence on heliolatitude of the thickness of the heliosheath. As a result, the model allows comparisons of modulation in the north and south hemispheres during both magnetic polarity cycles of the Sun, and from solar minimum to moderate maximum conditions. When comparing the computed spectra between polar angles of 55o (approximating the Voyager 1 direction) and 125o (approximating the Voyager 2 direction), it is found that at kinetic energies E < 1:0 GeV/nuc the effects of the assumed asymmetry in the geometry of the heliosphere on the modulated spectra are insignificant up to 60 AU from the Sun, but become increasingly more significant with larger radial distances to reach a maximum inside the heliosheath. In contrast, with E > 1:0 GeV/nuc, these effects remained insignificant throughout the heliosphere even very close to the heliopause (HP). However, when the enhancement of both polar and radial perpendicular diffusion coefficients off the equatorial plane is assumed to differ from heliographic pole to pole, reflecting different modulation conditions between the two hemispheres, major differences in the computed intensities between the two Voyager directions are obtained throughout the heliosphere. The model is further improved by incorporating new information about the HP location and the relevant heliopause spectrum for GCR Carbon at E < 200 MeV/nuc based on the recent Voyager 1 observations. When comparing the computed solutions at the Earth with ACE observations taken during different solar modulation conditions, it is found that it is possible for the level of modulation at the Earth, when solar activity changes from moderate maximum conditions to solar minimum conditions, to exceed the total modulation between the HP and the Earth during solar minimum periods. In the outer heliosphere, reasonable compatibility with the corresponding Voyager observations is established when drifts are scaled down to zero in the heliosheath in both polarity cycles. The effects of neglecting drifts in the heliosheath are found to be more significant than neglecting the enhancement of polar perpendicular diffusion. Theoretical expressions for the scattering function required for the reduction of the drift coefficient in modulation studies are illustrated and implemented in the numerical model. It is found that when this scattering function decreases rapidly over the poles, the computed A < 0 spectra are higher than the A > 0 spectra at all energies at Earth primarily because of drifts, which is unexpected from a classical drift modeling point of view. Scenarios of this function with strong decreases over the polar regions seem realistic at and beyond the TS, where the solar wind must have a larger latitudinal dependence. / PhD (Space Physics), North-West University, Potchefstroom Campus, 2015

The modulation of galactic cosmic ray (GCR) Carbon in a north-south asymmetrical heliosphere is studied, using a two-dimensional numerical model that contains a solar wind termination shock (TS), a heliosheath, as well as particle drifts and diffusive shock re-acceleration of GCRs. The asymmetry in the geometry of the heliosphere is incorporated in the model by assuming a significant dependence on heliolatitude of the thickness of the heliosheath. As a result, the model allows comparisons of modulation in the north and south hemispheres during both magnetic polarity cycles of the Sun, and from solar minimum to moderate maximum conditions. When comparing the computed spectra between polar angles of 55o (approximating the Voyager 1 direction) and 125o (approximating the Voyager 2 direction), it is found that at kinetic energies E < 1:0 GeV/nuc the effects of the assumed asymmetry in the geometry of the heliosphere on the modulated spectra are insignificant up to 60 AU from the Sun, but become increasingly more significant with larger radial distances to reach a maximum inside the heliosheath. In contrast, with E > 1:0 GeV/nuc, these effects remained insignificant throughout the heliosphere even very close to the heliopause (HP). However, when the enhancement of both polar and radial perpendicular diffusion coefficients off the equatorial plane is assumed to differ from heliographic pole to pole, reflecting different modulation conditions between the two hemispheres, major differences in the computed intensities between the two Voyager directions are obtained throughout the heliosphere. The model is further improved by incorporating new information about the HP location and the relevant heliopause spectrum for GCR Carbon at E < 200 MeV/nuc based on the recent Voyager 1 observations. When comparing the computed solutions at the Earth with ACE observations taken during different solar modulation conditions, it is found that it is possible for the level of modulation at the Earth, when solar activity changes from moderate maximum conditions to solar minimum conditions, to exceed the total modulation between the HP and the Earth during solar minimum periods. In the outer heliosphere, reasonable compatibility with the corresponding Voyager observations is established when drifts are scaled down to zero in the heliosheath in both polarity cycles. The effects of neglecting drifts in the heliosheath are found to be more significant than neglecting the enhancement of polar perpendicular diffusion. Theoretical expressions for the scattering function required for the reduction of the drift coefficient in modulation studies are illustrated and implemented in the numerical model. It is found that when this scattering function decreases rapidly over the poles, the computed A < 0 spectra are higher than the A > 0 spectra at all energies at Earth primarily because of drifts, which is unexpected from a classical drift modeling point of view. Scenarios of this function with strong decreases over the polar regions seem realistic at and beyond the TS, where the solar wind must have a larger latitudinal dependence. / PhD (Space Physics), North-West University, Potchefstroom Campus, 2015

The C-Band All-Sky Survey (C-BASS) is a 1 GHz bandwidth survey of the radio sky in both intensity and polarization at a frequency of 5 GHz and with a resolution of 0.8. Northern and Southern sky coverage is provided by antennas located at the Owen’s Valley Radio Observatory (OVRO) in California, and the MeerKAT support base in South Africa, respectively. The primary science goal of C-BASS is to provide a highly sensitive C-Band all sky intensity and polarization map to augment the WMAP/Planck surveys. Removal of foregound contamination will place a limit on the success of Cosmic Microwave Background (CMB) experiments that attempt to detect the B-Mode polarization of the CMB. We will provide a HEALPix map (N_side=128) with an r.m.s. noise of 0.13 mK/pixel in Stokes Q and Stokes U, and a confusion limited r.m.s. noise of 0.8 mK/pixel in Stokes I. Removal of foregrounds at the higher frequency CMB surveys will be significantly improved by this lower frequency constraint. This thesis describes the development of the C-BASS gain-stabilized receiver capable of making sensitive measurements of both galactic total intensity and polarization. The receiver features a novel digital backend to provide spectral detail across the frequency band of interest. The analog signal conditioning uses a double sideband mixer to mix the RF frequencies to a DC–1000 MHz baseband for digitization. By changing the mixer frequency and/ or duplicating the signal conditioning and digital hardware, the RF frequency coverage can be modified for other projects. I also describe the process of converting a 7.6 m telecommunications dish to a high performance radio astronomy platform. The discussion includes dish surface measurements, optical design, and the development of an inexpensive telescope servo controller. The antenna conversion process and receiver design can be used to significantly reduce capital costs of future experiments, which is especially useful for short timescale experiments. The African VLBI (Nordling, 2012) is currently following a similar route to repurpose antennas across the African continent.