Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-03-22T19:28:11Z No. of bitstreams: 1 JennyPaolaBravoCastrillon_TESE.pdf: 21271647 bytes, checksum: 8adb4a5df0dbdb4f20b049cb610cd4d2 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-03-23T21:59:10Z (GMT) No. of bitstreams: 1 JennyPaolaBravoCastrillon_TESE.pdf: 21271647 bytes, checksum: 8adb4a5df0dbdb4f20b049cb610cd4d2 (MD5) / Made available in DSpace on 2016-03-23T21:59:10Z (GMT). No. of bitstreams: 1 JennyPaolaBravoCastrillon_TESE.pdf: 21271647 bytes, checksum: 8adb4a5df0dbdb4f20b049cb610cd4d2 (MD5) Previous issue date: 2014-12-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / An?logas ?s manchas e f?culas fotosf?ricas solares, cuja visibilidade ? modulada por rota??o estelar, as regi?es ativas estelares consistem em grupos de manchas escuras na superf?cie da estrela e f?culas brilhantes causadas pelo seu campo magn?tico. Atualmente, as manchas estelares est?o bem estabelecidas como os principais marcadores usados para estimar o per?odo de rota??o estelar. Por outro lado, o comportamento din?mico das manchas tamb?m pode ser utilizado para analisar outros fen?menos relevantes, tais como a presen?a de atividade magn?tica e os seus ciclos. Para determinar o per?odo de rota??o estelar, identificar a presen?a de regi?es ativas e investigar se a estrela manifesta ou n?o rota??o diferencial, aplicamos dois m?todos: uma an?lise wavelet e um modelo de manchas. O procedimento wavelet tamb?m ? aplicado na an?lise de pulsa??es e na busca por assinaturas espec?ficas para esta variabilidade estelar particular dentre os diferentes tipos de estrelas vari?veis pulsantes. A transformada wavelet tem sido usada como uma ferramenta poderosa para o tratamento de v?rios problemas em astrof?sica. Neste trabalho mostramos que a an?lise em tempo-frequ?ncia das curvas de luz estelares, utilizando a transformada wavelet, ? uma ferramenta pr?tica para a identifica??o de rota??o, atividade magn?tica e assinaturas de pulsa??o. Apresentamos a composi- ??o espectral e as varia??es multiescala das s?ries temporais para quatro classes de estrelas: alvos dominados pela atividade magn?tica, estrelas com planetas, aquelas com tr?nsitos bin?rios, e estrelas pulsantes. Aplicamos a wavelet Morlet de 6 a ordem, que oferece alta resolu??o em tempo e frequ?ncia. Ao aplicar a transformada wavelet no sinal, obtemos os espectros de pot?ncia wavelet local e global. O primeiro ? interpretado como a distribui??o de energia do sinal no espa?o tempo-frequ?ncia, e o segundo ? obtido por integra??o temporal do mapa local. Sendo a transformada wavelet uma ferramenta matem?tica ?til para sinais n?o estacion?rios, esta t?cnica aplicada v ?s curvas de luz, obtidas a partir das miss?es espaciais Kepler e CoRoT, nos permite identificar claramente determinadas assinaturas para diferentes fen?menos. Em particular, foram identificados padr?es para a evolu??o temporal do per?odo de rota??o, bem como uma outra periodicidade decorrente dos efeitos das regi?es ativas nas curvas de luz analisadas; a continuidade de uma determinada escala (frequ?ncia) durante a maior parte do tempo pode representar um indicador de rota??o e atividade. Al?m disso, uma assinatura de padr?o de batimento no mapa wavelet local de estrelas pulsantes ao longo de todo o tempo tamb?m foi detectada. O segundo m?todo ? baseado na detec??o de manchas estelares durante os tr?nsitos de um planeta extrasolar que orbita sua estrela-m?e. Quando um planeta eclipsa sua estrela-m?e ? poss?vel detectar fen?menos f?sicos que ocorrem na superf?cie da estrela. Se uma mancha escura na superf?cie estelar ? eclipsada parcial ou totalmente, a luminosidade estelar integrada aumentar? ligeiramente. A an?lise da curva de luz medida durante um tr?nsito planet?rio nos permite inferir propriedades f?sicas das manchas estelares como o tamanho, a intensidade, a posi??o e a temperatura. Ao detectar a mesma mancha em tr?nsitos consecutivos, ? poss?vel obter informa??es adicionais, como o per?odo de rota??o estelar na latitude do tr?nsito planet?rio, a rota??o diferencial, e os ciclos de atividade magn?tica. Observa??es do tr?nsito planet?rio nas estrelas CoRoT-18 e Kepler-17 foram usadas para aplicar este modelo. / Analogous to sunspots and solar photospheric faculae, which visibility is modulated by stellar rotation, stellar active regions consist of cool spots and bright faculae caused by the magnetic field of the star. Such starspots are now well established as major tracers used to estimate the stellar rotation period, but their dynamic behavior may also be used to analyze other relevant phenomena such as the presence of magnetic activity and its cycles. To calculate the stellar rotation period, identify the presence of active regions and investigate if the star exhibits or not differential rotation, we apply two methods: a wavelet analysis and a spot model. The wavelet procedure is also applied here to study pulsation in order to identify specific signatures of this particular stellar variability for different types of pulsating variable stars. The wavelet transform has been used as a powerful tool for treating several problems in astrophysics. In this work, we show that the time-frequency analysis of stellar light curves using the wavelet transform is a practical tool for identifying rotation, magnetic activity, and pulsation signatures. We present the wavelet spectral composition and multiscale variations of the time series for four classes of stars: targets dominated by magnetic activity, stars with transiting planets, those with binary transits, and pulsating stars. We applied the Morlet wavelet (6th order), which offers high time and frequency resolution. By applying the wavelet transform to the signal, we obtain the wavelet local and global power spectra. The first is interpreted as energy distribution of the signal in time-frequency space, and the second is obtained by time integration of the local map. Since the wavelet transform is a useful mathematical tool for nonstationary signals, this technique applied to Kepler and CoRoT light curves allows us to clearly identify particular signatures for different phenomena. In particular, patterns were identified for the temporal evolution of the rotation period and other periodicity due to active regions affecting these light curves. In addition, a beat-pattern vii signature in the local wavelet map of pulsating stars over the entire time span was also detected. The second method is based on starspots detection during transits of an extrasolar planet orbiting its host star. As a planet eclipses its parent star, we can detect physical phenomena on the surface of the star. If a dark spot on the disk of the star is partially or totally eclipsed, the integrated stellar luminosity will increase slightly. By analyzing the transit light curve it is possible to infer the physical properties of starspots, such as size, intensity, position and temperature. By detecting the same spot on consecutive transits, it is possible to obtain additional information such as the stellar rotation period in the planetary transit latitude, differential rotation, and magnetic activity cycles. Transit observations of CoRoT-18 and Kepler-17 were used to implement this model.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-03-27T18:06:53Z No. of bitstreams: 1 RadmaAlmeidaDeFreitas_DISSERT.pdf: 5356592 bytes, checksum: 7490e6c529997950b911c26a922539c0 (MD5) / Approved for entry into archive by Monica Paiva (monicalpaiva@hotmail.com) on 2017-03-27T18:19:24Z (GMT) No. of bitstreams: 1 RadmaAlmeidaDeFreitas_DISSERT.pdf: 5356592 bytes, checksum: 7490e6c529997950b911c26a922539c0 (MD5) / Made available in DSpace on 2017-03-27T18:19:24Z (GMT). No. of bitstreams: 1 RadmaAlmeidaDeFreitas_DISSERT.pdf: 5356592 bytes, checksum: 7490e6c529997950b911c26a922539c0 (MD5) Previous issue date: 2015-07-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A presente disserta??o apresenta os fundamentos, o story board e a avalia??o de uma sess?o de planet?rio produzida com foco nas intera??es Terra-Sol, e direcionada para um p?blico geral. Para isto, nos baseamos em proposta anterior para a constru??o de sess?es e em reflex?es provenientes de dois eixos de discuss?o relacionados ? comunica??o da/sobre a ci?ncia em contextos de educa??o n?o formal. O primeiro eixo remete ? problematiza??o dos objetivos dessa comunica??o, destacando-se a ideia de populariza??o da ci?ncia. Nessa perspectiva, na produ??o da sess?o ?Viagem ao Sol? desenvolvemos sondagem, em Natal e cidades do interior do estado, sobre ideias da popula??o a respeito do Sol; e desenvolvemos pesquisas sobre essa tem?tica em cord?is, al?m das fontes cient?ficas. O segundo eixo remete ? constru??o de conhecimentos em situa??es de ?aprendizagem por livre escolha? conforme o Modelo Contextual de Aprendizagem. Esse modelo ressalta o papel de organizadores pr?vios em exposi??es de museus. A partir desse conceito, adotamos a escolha de uma mensagem geral ?Os fen?menos que acontecem no Sol podem afetar nossas vidas?, e de n?cleos de informa??o, a fim de orientar a estrutura??o e a transposi??o das ideias cient?ficas veiculadas na sess?o, bem como a avalia??o desta. Como avalia??o, utilizou-se um estudo realizado durante uma Mostra de Astronomia com o Planet?rio Digital M?vel da UFRN - Barca dos C?us no interior do estado. Tal estudo fez uso da ferramenta Mapa de Significado Pessoal, associada a entrevistas. Como resultados principais da avalia??o, destacamos a predomin?ncia, nos mapas ap?s a sess?o, da ideia de que o Sol ? importante para nossas vidas e que nos influencia de diversas formas; al?m disso, as informa??es da sess?o relacionadas ? Astronomia cotidiana estiveram entre as mais citadas nos mapas. Ap?s a sess?o tamb?m apareceram algumas ideias sobre a Din?mica solar, as quais haviam sido identificadas como lacunas na cultura geral da popula??o. Constatou-se, contudo, poucas ideias que explicitassem uma rela??o entre o Sol e fen?menos magn?ticos. Uma implica??o importante da avalia??o da sess?o foi a identifica??o dos momentos prop?cios para intera??es com o p?blico, durante a mesma. Dentre estes momentos destaca-se: a discuss?o acerca da produ??o de energia no interior do Sol; e a discuss?o sobre as manchas solares como resultado da din?mica solar.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-07-03T14:11:15Z No. of bitstreams: 1 MiltonGomesDeSouzaNetto_DISSERT.pdf: 17163746 bytes, checksum: 1f47747a8a9396780f7b8050a1ea7ac9 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-07-10T13:55:47Z (GMT) No. of bitstreams: 1 MiltonGomesDeSouzaNetto_DISSERT.pdf: 17163746 bytes, checksum: 1f47747a8a9396780f7b8050a1ea7ac9 (MD5) / Made available in DSpace on 2017-07-10T13:55:47Z (GMT). No. of bitstreams: 1 MiltonGomesDeSouzaNetto_DISSERT.pdf: 17163746 bytes, checksum: 1f47747a8a9396780f7b8050a1ea7ac9 (MD5) Previous issue date: 2016-10-28 / Motivados pelo crescente aumento no n?mero de projetos de pesquisas em exoplanetase pela escassez de modelos matem?ticos que levem em considera??o ru?dos n?o-Gaussianose correlacionados na fotometria dos dados, n?s analisamos a altera??o do par?metro estat?stico expoente de Hurst, H, em s?ries temporais com diversos tipos de ru?do astrof?sico,com e sem a presen?a de um tr?nsito planet?rio. Neste sentido, determinamos o valor doexpoente de Hurst para duas curvas de luz provenientes do banco p?blico de dados da miss?o CoRoT. Usamos, para estimar o valor de H, dois m?todos: a an?lise R/S (sigla do ingl?s rescaled range) e a transformada r?pida de Fourier, fft (sigla do ingl?s fast Fou-rier transform). Para isso, desenvolvemos um simulador de ru?do astrof?sico onde geramos s?ries temporais de diversos tipos de ru?do e estimamos o valor de H para todas as s?ries simuladas. Na sequ?ncia, geramos um tr?nsito planet?rio sint?tico e o inserimos nos ru?dos para ent?o recalcularmos o valor de H. Notamos que a presen?a do tr?nsito planet?rio alterou significativamente o valor do expoente de Hurst e que o m?todo da an?lise R/S ? mais adequado do que o m?todo da transformada r?pida de Fourier quando se trata de s?ries temporais na presen?a de ru?dos n?o-Gaussianos. Verificamos que o expoente de Hurst pode ser um descriminante poderoso para distinguir s?ries temporais com comportamento variado, em particular, a distin??o entre s?ries apresentando tr?nsito. Estimamos ainda o expoente de Hurst para 30 estrelas da base de dados p?blicos da miss?o Kepler e o relacionamos com o per?odo orbital de planetas presentes nesses sistemas.

Orientador: Maurício Compiani / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-19T00:25:03Z (GMT). No. of bitstreams: 1 Garcia_FabianaBurgosTakahashi_M.pdf: 5270236 bytes, checksum: 1fa1e53fc6bf45eb1dcc6fa74e637d09 (MD5) Previous issue date: 2011 / Resumo: A presente dissertação tem seu olhar voltado para o currículo da disciplina escolar química e sua relação com as geociências. Este trabalho foi desenvolvido no contexto do projeto apoiado pela Fundação de Amparo à Pesquisa de São Paulo (FAPESP) - Ensino Público intitulado "Elaboração de conhecimentos escolares e curriculares relacionados à ciência, à sociedade e ao ambiente na escola básica com ênfase na regionalização a partir dos resultados de projeto de Políticas Públicas", cujo recorte de análise era a bacia do Ribeirão das Anhumas, onde está inserida a escola estadual que foi cenário principal desta dissertação e onde atuavam professores, alunos e acadêmicos. Baseando metodologicamente na perspectiva da pesquisa-ação sugerida por Mckernan principalmente, foi possível sistematizar este trabalho de modo que a importância do professor na elaboração do currículo fosse evidenciada, como propõe o mesmo autor. Neste sentido, a pesquisadora, professora da escola básica, voltou-se para seus instrumentos de trabalho questionando-os e sugerindo alterações. Então foi realizada uma revisão dos documentos oficiais que contribuíram para a elaboração da Proposta Curricular do Estado de São Paulo para o Ensino de Química (PCEQ) sob o olhar da contextualização e interdisciplinaridade visando mostrar que as discussões acerca da elaboração de currículos com esta conotação não são recentes. Além disso, os cadernos do professor e do aluno que complementam a PCEQ, e o livro didático utilizado em sala pela pesquisadora também foram analisados abordando a presença ou não do tema "Química e Litosfera" bem como o tratamento dado a esta temática quando presente no material, uma vez que é sugerido nas Orientações Complementares aos Parâmetros Curriculares Nacionais (PCN+), porém ausente na PCEQ. Por isso que em meio a discussões e reflexões colaborativas do subgrupo Ensino-Aprendizagem, nas quais a interdisciplinaridade era discutida e utilizada como referencial para elaborar e desenvolver atividades escolares dentro do contexto local, e também com base nas lacunas encontradas durante estas análises, é que foi possível complementar o referido material. Dentre todas as atividades, podemos dizer que o trabalho de campo foi talvez o mais importante, afinal, foi possível perceber que os alunos tinham conhecimento para explicar a formação dos solos a partir das interações que ocorrem no ambiente, partindo de observações da paisagem local. Desta forma, pudemos nos aproximar dos objetivos de incorporar ao currículo de química o tema citado utilizando conhecimentos sobre a Bacia do Ribeirão das Anhumas, local onde a escola se insere. Enfim, a inserção do tema faltante na PCEQ vem suprir necessidades de conteúdos, enquanto promove junto com a abordagem local a superação de problemas reais e escolares, e tudo isso dentro de uma dinâmica de colaboração entre os atores envolvidos naquele cenário / Abstract: This dissertation focuses the curriculum of the Chemistry discipline and its relation with the Geosciences. This paper was developed in the context of the FAPESP Public Teaching Project entitled "Construction of school and curricular knowledge relative to science, society and environment at primary and secondary school with emphasis in the local conditions from results of public politicians projects" which focused its analysis in the basin of the Brook of Anhumas where the state school is located. This school was the scenario of this research whose professors, teachers and students maintained a collaboration relationship and learning to the development of this study. Using Mckerman methodological approach of action-research, it became possible to design a system of work with a view to emphasize the importance of the teacher in the elaboration of the curricular content, as the author proposes. Therefore, the researcher who is also a teacher at the secondary school, looked at her working tools, questioned them and suggested changes. Official documents that contributed to the elaboration of PCEQ were also reviewed in the light of context and interdisciplinary relations with a view to show that discussions about curricular contents using this concept are not new. Teacher's and student's notebooks which complement the PCEQ and the didactic book used by the researcher were also analyzed to ascertain whether or not they contained the theme "Chemistry and the Lithosphere" as well as how the subject is mentioned in the books, since its use is suggested in the PCN+ but is, however, absent from the PCEQ. Based on the collaborative discussions of the sub-group "Teaching-Learning", where the subject of interdisciplinarity was discussed and used as reference to elaborate and develop school activities within the local context, and also using the gaps found during these analyses it was possible to develop complementary material. Amongst all the activities we can say that the field work was perhaps the most important, as it made possible to perceive that the students had acquired the knowledge to explain the soil formation from the interactions that occur in the environment using as the starting point for their comments the local landscape. Therefore we could reach our goal of incorporating to the Chemistry curricular studies the subject above mentioned using the data of the basin of Brook of Anhumas where the school is located. At last the insertion of the missing subject in the PCEQ comes to suffice necessities of contents while it makes possible to overcome, with a localized approach, existing school problems promoting a collaborative dynamics among all the participants involved in that particular scenario / Mestrado / Ensino e Historia de Ciencias da Terra / Mestre em Ensino e Historia de Ciencias da Terra

HD 141569 A is a pre-main sequence B9.5 Ve star surrounded by a prominent and complex circumstellar disk, likely still in a transition stage from protoplanetary to debris disk phase. Here, we present a new image of the third inner disk component of HD 141569 A made in the L' band (3.8 mu m) during the commissioning of the vector vortex coronagraph that has recently been installed in the near-infrared imager and spectrograph NIRC2 behind the W.M. Keck Observatory Keck II adaptive optics system. We used reference point-spread function subtraction, which reveals the innermost disk component from the inner working distance of similar or equal to 23 au and up to similar or equal to 70 au. The spatial scale of our detection roughly corresponds to the optical and near-infrared scattered light, thermal Q, N, and 8.6 mu m PAH emission reported earlier. We also see an outward progression in dust location from the L' band to the H band (Very Large Telescope/SPHERE image) to the visible (Hubble Space Telescope (HST)/STIS image), which is likely indicative of dust blowout. The warm disk component is nested deep inside the two outer belts imaged by HST-NICMOS in 1999 (at 406 and 245 au, respectively). We fit our new L'-band image and spectral energy distribution of HD 141569 A with the radiative transfer code MCFOST. Our best-fit models favor pure olivine grains and are consistent with the composition of the outer belts. While our image shows a putative very faint point-like clump or source embedded in the inner disk, we did not detect any true companion within the gap between the inner disk and the first outer ring, at a sensitivity of a few Jupiter masses.

The Diploma thesis deals with the topic of measuring the standard of living and quality of life in selected countries in Europe and further highlights the differences in the Visegrad countries. The aim of the work is to describe components of comprehensive concept of quality of life based on studies of specified literature. Moreover it describes the most frequently used methods for measuring quality of life. The methodological part describes the used methods. Secondary analysis and a design of own methodology to compare the standard of living is the object of practical part of Diploma thesis.

Be moving, seek, hunt for sth, can´t find it so far, that is a promise of paradise, or a paradise itself. Mobility as a protest, pursuit of adventure, searching for escape, authenticity or identity.

Les observations de centaines de systèmes d’exoplanètes nous ont fourni un large échantillon de configurations orbitales. Les périodes orbitales figurent parmi les données les mieux connues et les plus étonnantes. Les Super-Terres, ces planètes caractérisées par une masse entre 1 et 20 masses terrestres et une période typiquement de moins de 100 jours, sont présentes autour de la plupart des étoiles. La distribution des rapports de leurs périodes orbitales défie les astrophysiciens : pendant leur formation et migration au sein de leur disque protoplanétaire, elles devraient former des chaînes de résonances de moyen mouvement, c’est-à-dire que les rapports des périodes orbitales de planètes voisines devraient être proches de fractions simples. Toutefois, la plupart des systèmes de Super-Terres ne sont pas résonants. Dans cette thèse, je traite les aspects clés des chaînes résonantes : leur formation, leur évolution et leur stabilité. Premièrement, j’introduis les idées modernes en théorie de formation planétaire, et les méthodes utilisées dans la thèse : la mécanique Hamiltonienne, le problème planétaire et la théorie perturbative. Deuxièmement, je présente le processus de capture en résonance de moyen mouvement du premier ordre k : k − 1 par migration convergente des planètes, avec une nouvelle description analytique de l’évolution planétaire qui en suit, et je décris la dynamique résonante dans le plan orbital commun. La description analytique est confirmée par des intégrations N-corps qui incluent les interactions disque-planète. Ensuite, je me base sur des résultats existants concernant l’évolution dissipative de deux planètes en résonance qui engendre la divergence de leurs demi-grands axes. Par une approche similaire, je présente une méthode statistique qui permet de déterminer dans quelle mesure l’architecture observée d’un système de trois planètes est compatible avec une histoire dynamique résonante dissipative. Je considère par la suite la stabilité des chaînes résonantes. Des études antérieures ont montré que l’absence de systèmes exoplanétaires résonants n’est pas en contradiction avec le modèle de capture en résonance par migration dans le disque, si une phase d’instabilité est très commune après la disparition du disque. On observe un taux d’instabilité plus élevé dans les systèmes synthétiques plus compacts et peuplés par des planètes plus massives. Des simulations N-corps dédiées à l’étude de la stabilité des chaînes résonantes ont montré qu’il y a une masse planétaire maximale qui garantit la stabilité ; cette masse limite diminue si les planètes sont plus massives et/ou si la chaîne résonante est plus compacte. J’étudie la stabilité des chaînes résonantes de planètes en fonction de leur masse commune, et j’examine de façon analytique et numérique des cas spécifiques de systèmes comprenant deux ou trois planètes. Je découvre un mécanisme dynamique qui peut déclencher une excitation du système, et qui mène à une phase de rencontres proches et collisions. Ce mécanisme se généralise à différents nombres de planètes et/ou à des chaînes résonantes plus ou moins compactes, et donne une prédiction analytique de la masse critique qui est en accord qualitatif avec les expériences numériques mentionnées précédemment. Enfin, je décris un scénario dynamique qui peut expliquer la pollution des naines blanches en éléments lourds. Les systèmes planétaires compacts peuvent devenir instables pendant la phase de perte de masse qui marque la fin de l’évolution stellaire, et les impacts entre planètes génèrent des débris. En m’appuyant sur des résultats précédents, je montre que l’excentricité orbitale des débris qui résident en résonance de moyen mouvement avec une planète externe peut devenir suffisamment élevée pour que les débris soient engloutis par l’étoile, ce qui peut expliquer la pollution observée. / Observations of hundreds of exoplanetary systems have produced a huge sample of orbital configurations, and the orbital periods are one of their better constrained and most astonishing properties. A common type of exoplanets are the Super-Earths, which have a mass between 1 and 20 Earth masses and a typical period of less than 100 days. The period ratio distribution of these planets poses a challenge to astrophysicists: during their formation, still embedded in the protoplanetary disc, we expect them to form chains of mean motion resonances, where the period ratio of neighbouring planets is close to a low-integer ratio. However, most Super-Earth systems are not close to resonance. In this thesis, I discuss key dynamical aspects of resonant chains: their formation, their evolution and their stability. I first give an overview of our current understanding of planetary formation, and an introduction of the methods used in the thesis: the tools of Hamiltonian dynamics, the planetary problem and perturbation theory. Then, I present the process of capture of planets migrating in protoplanetary discs into first order k : k − 1 mean motion resonances, including a novel analytical description of the corresponding planetary evolution, and I describe the relevant aspects of resonant dynamics in the planar approximation. The analytical treatment is supported by numerical N-body simulations which include the planet-disc interactions. Next, I expand on previous results on two-planet dissipative evolution in mean motion resonance and the resulting divergence of the planets’ semi-major axes. With a similar approach, I present a statistical method which allows to determine to what extent the observed architecture of a three-planet system is compatible with a dissipative resonant dynamical history. I then address the main problem of the stability of resonant chains. Previous works have shown that the over-all lack of resonances in the exoplanet sample is not in contradiction with resonant capture, if a post-disc phase of planetary instabilities is extremely common. Higher rates of instabilities are observed in synthetic systems where planets are most massive and the configurations most compact. Specific N-body experiments on the stability of resonant chains found that there is a critical planetary mass allowed for stability, which decreases with increasing number of planets and/or increasing value of k in the chain. The origin of these instabilities was however not discussed. I study the stability of resonant chains of equal-mass planets in terms of their mass, investigating analytically and numerically specific cases of two- and threeplanet systems. I find a dynamical mechanism which can trigger an excitation of the system, leading to mutual close-encounters and collisions. This can be generalised to an arbitrary number of planets and/or value of k in the resonant chain, and gives an analytical prediction for the critical mass allowed for stability which agrees qualitatively with the aforementioned numerical experiments. Finally, I describe a dynamical scenario that can explain the pollution of White Dwarfs with heavy elements. The idea is that compact planetary systems become unstable during the mass-loss phase characterising the end of the stellar evolution, so that impacts among planets lead to the generation of collisional debris. Expanding on previous works, I show that debris residing in mean motion resonance with an outer planetary perturber can have their orbital eccentricity excited to largeenough values to be engulfed by the host star, causing the observed pollution.

Title: Correlation properties of magnetosheath fluctuations Author: Olga Gutynska Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Jana Šafránková, DrSc. e-mail address: Jana.Safrankova@mff.cuni.cz Abstract: This thesis deals with fluctuations of the magnetic field (MF) and plasma density in different magnetosheath locations. The statistical study of the correlation length of these quantities has shown that these lengths are surprisingly low for both the ion flux and MF (approx. 1 RE). However, the correlation length increases with an increasing correlation between the magnetosheath and interplanetary magnetic fields (IMF). Further, we have found that the correlation length of MF fluctuations depends on the solar wind speed, on a correlation between IMF and magnetosheath MF fluctua- tions, and on the amplitude of fluctuations. The statistical study of radial profiles of cross-correlations between MF and plasma density at the subsolar and flank regions based on Cluster and THEMIS magnetosheath observa- tions revealed better correlations toward the magnetopause. A study of the modification of the IMF direction in the magnetosheath has shown that a reliable prediction of the magnetosheath BZ sign requires |IMF BZ| > 2 nT and that this prediction is more precise during solar minimum....

No description available.