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published_or_final_version / Physics / Doctoral / Doctor of Philosophy

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Bibliography: leaves 117-124 / 124 leaves,[31] leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1984

Includes bibliographical references / 119 leaves, [67] leaves : ill., maps ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of physics, University of Adelaide, 1983

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 307-319).

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Nesta tese investigamos uma possível componente de partículas previstas por modelos além do modelo padrão da física de partículas, como por exemplo o massive gluino LSP, nos raios cósmicos de altíssimas energias (UHECR). Nosso objetivo é determinar os sinais experimentais em telescópios de fluorescência devidos a hádrons exóticos massivos e neutros, genericamente denominados de UHECRons. Para simular chuveiros iniciados por essa classe de partículas, alteramos o pacote Aires de simulação de chuveiros atmosféricos e o modelo hadrônico Sibyll. Estes chuveiros foram utilizados como entrada em simulações de telescópios de fluorescência por nós desenvolvidas, obtendo-se assim as distribuições dos observáveis desses chuveiros exóticos. A partir da comparação entre as características de chuveiros iniciados uhecrons e prótons, desenvolvemos métodos para a separação de sinais entre esses dois tipos de partículas. Esses métodos podem ser utilizados em uma análise inicial, com o intuito de procurar por sinais de partículas exóticas nos dados reais de observatórios de UHECR. / In this thesis we investigate a possible component of particles predicted by models beyond the standard model of particle physics, like the massive gluino LSP, in the ultra high energy cosmic rays (UHECR). Our objective is to determine the experimental signals on fluorescence telescopes due to exotic massive and neutral hadrons, generically called UHECRons. To simulate showers initiated by this class of particle, we altered the shower simulation package Aires and the hadronic model Sibyll. These showers were used as input in our simulations of fluorescence telescopes, thus obtaining the distribuitons of the observables for these exotic showers. By comparing the characteristics of showers initiated by uhecrons and protons, we developed methods to distinguish the signals between these two particles. These methods can be used in an initial analysis in order to look for signals of exotic particles in the real data of UHECR observatories.

Les météoroïdes, les astéroïdes et les comètes ont été en interaction permanente avec la Terre pendant son existence. Lorsqu'un objet, tel qu'une comète ou un astéroïde, tourne autour du Soleil, il peut laisser des fragments de matière derrière lui. Il y a une relation implicite entre les fragments et leurs corps parents. Le champ gravitationnel de la Terre capte les fragments et quelques fois le matériel extraterrestre est retrouvé au sol sous la forme des météorites. L'étude de ces objets et le lien entre eux peuvent aider à comprendre les conditions de formation et d'évolution du Système solaire, les conditions de développement de la vie sur Terre, les processus chaotiques dans le Système solaire, la sécurité de la Terre et peut-être, l'industrie spatiale.Tous les objets dans le Système solaire sont caractérisés par leurs orbites et les flux de météoroïdes ont des orbites similaires avec les objets qui les produisent. Pour cette raison, la méthode la plus courante d'identification du corps parental est basée sur les similarités des orbites, également appelées critères de discrimination ou critères-D. Dans mon travail, j'ai utilisé trois critères D-Criteria pour l'association des corps parents. Je définis un seuil pour chaque mesure en utilisant une nouvelle méthode de sélection de seuil. En outre, j'ai étudié les objets associés stabilité orbitale, dans le sens du temps de Lyapunov et leurs propriétés physiques. En raison des similitudes entre les flux de météorites et leurs corps parents, il est nécessaire que les associations appartiennent à la population d'astéroïdes géocroiseurs. L'observation de cette population d'objets est cependant difficile. La géométrie favorable pour les observations d'un géocroiseur est limité a trois ou cinq fois par siècle. Pour cette raison j'ai créé un programme d'observation, qui vise à obtenir des données physiques pour les objets associés qui n'ont pas de données physiques. Lors de mes recherches, j'ai pu associer 296 géocroiseurs à 28 pluies de météores; parmi eux, 73 astéroïdes satisfaisants les trois critères utilisés. Du point de vue dynamique, mon échantillon contient 82 % d'astéroïdes de type Apollo et 7 % sont classés comme potentiellement dangereux, 15,3 % sont sur des orbites cométaires et 84,3 % sur des orbites d'astéroïdes. Du point de vue des données physiques, j'ai trouvé deux astéroïdes qui sont des rotateurs rapides, donc ils ne peuvent pas générer de météores. D'un autre côté, j'ai également trouvé un astéroïde binaire associé et un astéroïde tumbling, des objets avec une forte probabilité d'être des corps parents. J'ai également réussi à trouver des similitudes entre 5 météorites et 5 astéroïdes associés avec des données physiques et j'ai obtenu des données d'observation pour trois astéroïdes associés. / Meteoroids, asteroids, and comets have been permanently interacting with Earthduring its existence. When an object, such as a comet or an asteroid, revolve around the Sun it may leave fragments of matter behind it and if this object is in Earth’s proximity, those fragments are gathered by the planet gravity. The study of these objects and the link between them can help in the understanding of the formation and evolution conditions of the Solar System, the conditions of developing the life on Earth, the chaotic processes in the Solar System, Earth security and maybe, in future, space industry.All objects within the Solar System are characterized by their orbits andthe meteoroid streams have similar orbits with the objects that produce them. For that reason the most common method of parent body identification is based onorbits similarities, also known as discrimination criteria or D-Criteria. In my work I used three D-Criteria metrics for parent body association. I set a threshold for each metric by using a new threshold selection method. Moreover, I investigated the associated objects orbital stability, in the Lyapunov time sense and their physical properties.Due to the similarities between meteoroid streams and their parent bodies,it is required for the associations to belong to Near Earth Asteroids population. But for this population is difficult to obtain data. The favorable geometry for these objects observations occurs five times per century. For this reason was created an observational program, that aims to obtain physical data for the associated objects that do not have physical data.My results consist from 296 asteroids that were associated with 28 meteorshowers, from which 73 asteroids satisfied all the criteria used. From the dynamical perspective, my sample contains 82% of Apollo asteroids and 7% are classified as potential hazardous, 15.3% are on cometary orbits and 84.3% are on asteroidal orbits. From the physical data perspective, I found two asteroids that are fast-rotators, therefore they can not generate meteors. On the other hand, I also found associated one binary asteroid and one tumbling asteroid, objects with a high probability of being parent bodies.I also managed to find similarities between 5 meteorites and 5 associatedasteroids with physical data and I obtained observational data for three associated asteroids.

This thesis is concerned with the observation and study of meteors with a narrow beam VHF radar operated by the University of Adelaide at the Buckland Park research station, in particular the study of the structure and characteristics of meteor showers and the geocentric speeds of meteors. There have been several observations of meteors with the radar previously (Steel & Elford 1991, Cervera 1996, Taylor et al. 1996), but this is the first with an automated data analysis directed to a systematic study of the properties of meteor showers. The Buckland Park VHF radar offers significant advantages over the wide beam radars traditionally used for meteor observation. The narrow beam, while reducing the collecting area of the radar, allows observations of much lower electron line densities than a wide beam radar of similar power. It also allows the determination of meteor shower radiants by the use of the radar response function. Pulse repetition frequencies of up to 2000 Hz allow excellent time resolution, and the ability to record in-phase and quadrature data allows the phase information to be used. This phase information is important as it allows the use of the phase information to accurately determine radial wind drifts, and the atmospheric speeds of meteoroids. During 1998, 1999 and 2000, observations were made of a number of meteor showers and the sporadic background. These showed that the η-Aquarid meteor shower was active in these years, and the Orionid and the Leonid showers were detected in 1999. Analysis of the η-Aquarid activity revealed multiple peaks which show that the shower is produced by at least four distinct "filaments", subsets of the meteoroid stream which produces the shower. Not only does the stream have spatial structure, containing groups of particles in different orbits, but also the presence or absence of the peaks in a random fashion from day to day shows that the filaments are themselves made up of clumps of particles. The radar response function is developed and used to determine radiants for the four η-Aquarid filaments. Evidence is given of a significant number of meteors detected at heights which are above the "radar ceiling", a height at which the theoretical initial radius attenuation factor is near zero for radars operating at the frequency of the Buckland Park VHF Radar, and underdense echoes should be impossible to detect. Investigation showed that over 60 % of meteor trails at heights above the ceiling (105 km) were underdense. Not only does the expected meteor height distribution extend up to 130 km, but also another distribution, peaking at 145 km is uncovered. Diffusion coefficients estimated from the decay of echoes are compared to theoretical calculations. There is a general agreement, but a number of meteor trails show slower diffusion than expected. This is attributed to the effect of the Earth's magnetic field. Three methods are used to determine meteoroid speeds using the phase data, each applying to a different type of meteor echo, and in combination, speeds could be determined for over 90 % of all meteor echoes. The first, the pre-t0 method can be applied to transverse meteor echoes with great success, although it may underestimate the speed of weak echoes with speeds under 15 km s-¹. Using the Cauchy approximations to the Fresnel integrals allows speed determination from head echoes which were aliased near the t0-point. Meteor trails which form at a small angle to the boresight of the radar beam are called "down-the-beam" echoes, and a new method is developed to determine the meteoroid speed and deceleration from these. The speed measurements of meteors detected during the η-Aquarids show a strong peak in the distribution at 66 km s-¹, as well as a smaller peak at 50 km s-¹, which may due to a minor shower. The sporadic background shows a broad peak at 25 km s-¹, with a smaller peak at 58 km s-¹. Distributions of the speed of meteors in the sporadic background show good agreement with previous observations (McCrosky & Posen 1961, Nilsson 1962, Elford et al. 1995, Cervera 1996), with the exception of meteoroid speeds smaller than 15 km s-¹, which can be underestimated by the pre-t0 technique. / Thesis (Ph.D.)--Physics and Mathematical Physics, 2002.