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Equatorial plasma bubbles (EPBs) are large structures consisting of depleted plasma that generally form on the nightside of Earth's ionosphere along magnetic field lines in the upper thermosphere/ionosphere. While referred to as `bubbles', EPBs tend to be longer along magnetic latitudes and narrower along magnetic longitudes which are on the order of thousands and hundreds of kilometers, respectively. EPBs are a well documented occurrence with observations spanning many decades. As such, much is known about their general behavior, seasonal variation of occurrences, increasing/decreasing occurrences with increasing/decreasing solar activity, and their ability to interact and interfere with radio waves such as GPS. This dissertation expands on this understanding by focusing on the detection and tracking of EPBs in the upper thermosphere/ionosphere along equatorial to low latitudes. To do this, far ultraviolet (FUV) emission observations of the recombination of O$^+$ with electrons via the Global-Scale Observations of the Limb and Disk (GOLD) mission are analyzed. GOLD provides consistent data from geostationary orbit with the eastern region of the Americas, Atlantic, and western Africa. The optical data can be used to pick out gradients in brightness along the 135.6 nm wavelength which correlate with the location of EPBs in the nightside ionosphere. The dissertation provides a novel method to look at and analyze 2-dimensional data with inconsistent time-steps for EPB detection and tracking. During development, preprocessing of large scale (multiple years) data proved to be the largest time sync. To that end, this dissertation tests the possibility of using convolution neural networks for detection of EPBs with the end goal of reducing the amount of preprocessing necessary. Further, data from the Ionospheric Connection Explorer's (ICON's) ion velocity meter (IVM) are compared to EPBs detected via GOLD to understand how the ambient plasma around the EPBs behave. Along with the ambient plasma, zonal and meridional thermospheric winds observed by ICON's Michelson Interferometer for Global High-resolution Thermospheric Imaging (MIGHTI) instrument are analyzed in conjunction with the same EPBs to understand how winds coincident with EPBs behave. An analysis of winds before EPBs form is also done to observe the potential for both zonal and meridional winds' ability to suppress and amplify EPB formation. / Doctor of Philosophy / Equatorial plasma bubbles (EPBs) are large structures that generally form during post- sunset along Earth's magnetic equator. While referred to as `bubbles', EPBs tend to be thousands of kilometers from north to south and hundreds of kilometers from east to west and well over a thousands kilometers in altitude. EPBs are a well documented occurrence with observations spanning many decades. This includes their ability to interfere with radar and GPS. This dissertation expands on the scientific community's understanding by focusing on the detection and tracking of EPBs along the magnetic equator. To do this, observations from the NASA Global-Scale Observations of the Limb and Disk (GOLD) mission are analyzed. GOLD provides consistent observations looking over the eastern region of the Americas, Atlantic, and western Africa. A unique method to look at and analyze this data for EPB detection and tracking is developed. This dissertation also tests the possibility of using machine learning for detection of EPBs. Further, data from the NASA Ionospheric Connection Explorer (ICON) mission is compared to EPBs detected via GOLD to understand how the behavior of the upper atmosphere and the conductive region therein, known as the ionosphere, interact with the EBPs themselves.

La finalidad de esta tesis es la obtención de las distribuciones de velocidades, presiones y temperaturas en la convección forzada de flujos compresibles en situaciones bidimensionales y de estabilización. Es a partir de estos valores que se determina la fricción y la transferencia de calor entre el fluido y el contorno o canalización.La tesis consta de cinco capítulos. En el primero, de carácter introductorio, se plantea la problemática de resolución de las ecuaciones que describen el comportamiento del flujo. Se analizan dos niveles de modelización. De una parte, y en base al concepto de capa límite introducido por L. Prandtl, se divide el dominio por el que circula el flujo en dos zonas: unas delgadas regiones próximas a los contornos sólidos en los que la fricción y la transferencia de calor son factores condicionantes, y el resto del dominio en el que el flujo puede considerarse como no viscoso, pudiéndose despreciar los efectos de la fricción y de la transferencia de calor. En el segundo nivel de modelización se plantea la resolución directa de las ecuaciones de continuidad, cantidad de movimiento y energía en todo el dominio.Los capítulos segundo, tercero y cuarto están dedicados al primer nivel de modelización indicado. En el segundo capítulo se resuelve el flujo potencial compresible en base a la discretización del dominio mediante la generación de mallas adaptables a los contornos. Se analizan diferentes criterios de discretización de las ecuaciones siendo los resultados numéricos obtenidos contrastados entre si y con los que se derivan del empleo de mallas de discretización rectangulares. El tercer capítulo trata de la resolución de las capas límites hidrodinámicas y térmicas mediante la integración numérica de la ecuaciones de conservación. Para el análisis de las capas límite turbulentas se ha utilizado los conceptos de viscosidad turbulenta y conductividad térmica turbulenta, empleándose expresiones semiempíricas en la descripción de dichas cantidades. Se estudian diversas situaciones contrastándose los resultados numéricos obtenidos con los que se derivan de estudios experimentales presentados por distintos autores. En el cuarto capítulo se efectúa la resolución conjunta de la zona potencial y de las capas límite en el marco de un algoritmo global de resolución. A modo ilustrativo se ha realizado el estudio del flujo de aire en una tobera o canalización convergente, analizándose aspectos tales como la compresibilidad del flujo y la transferencia de calor entre el fluido y los contornos sólidos limitantes. Los resultados que se derivan de la resolución numérica, supuestos los contornos adiabáticos, son contratados con los obtenidos experimentalmente en esta tesis y en una unidad de soplado del laboratorio. En el quinto y último capítulo se aborda el segundo nivel de modelización arriba indicado, si bien la atención se centra en ecuaciones genéricas del tipo convección-difusión. Así, partiendo de una distribución de velocidades conocida, se realiza la resolución de dicha ecuación en base a la generación de sistemas ortogonales de coordenadas curvilíneas coincidentes con las propias líneas de corriente del flujo. La precisión y zonas de aplicación del método numérico son puestas de manifiesto en situaciones singulares de solución analítica conocida. Los resultados obtenidos son satisfactorios en un amplio rango de números de Peclet, y claramente superiores a los que se derivan del empleo de mallas de discretización rectangulares. / The purpose of this thesis is to obtain velocity, pressure and temperature distributions in compressible flows under steady-state conditions.The thesis has five chapters. The first one introduces the mathematical formulation and two main strategies to solve the governing equations. The first one is based on a zonal model, which solved in a coupled manner the Euler and the boundary layer equations. The second level is based on the resolution of the Navier-Stokes equations in the whole domain.The next three chapters are devoted to the first level of modelization mentioned above. The second chapter solves the Euler equations of the inviscid flow based on the discretization of the domain by means of body-fitted meshes. Numerical solutions are also carefully verificated based on grid refinement techniques. Several numerical criteria for the discretization of the equations are presented and contrasted. The third chapter deals with the numerical integration of the hydrodynamic and thermal boundary layer equations using algebraic turbulence models extended to compressible flows. A study of the different parameters which influence on flow is presented.In the fourth chapter, a coupled procedure of the two zones (inviscid zone and boundary layers) is proposed within the framework of a global algorithm. By way of illustration the study of the compressible flow in a converging channel is carried out. Different aspects related to the compressibility of the flow and the heat transfers exchanged with the solid boundaries are studied. The mathematical model is validated against experimental results obtained in a specially designed set-up.In the fifth and final chapter, the second level of modelization is presented but only the part which refers to generic convection-diffusion equations. Thus, starting from a known velocity distribution, an analysis of different standard numerical schemes is performed together with a proposal of a new scheme to reduce the numerical false diffusion effects.

Les réseaux de capteurs sans fil d'images sont utilisés aujourd'hui dans de nombreuses applications qui diffèrent par leurs objectifs et leurs contraintes individuelles. Toutefois, le dénominateur commun de toutes les applications de réseaux de capteurs reste la vulnérabilité des noeuds-capteurs en raison de leurs ressources matérielles limitées dont la plus contraignante est l'énergie. En effet, les technologies sans fil disponibles dans ce type de réseaux sont généralement à faible portée, et les ressources matérielles (CPU, batterie) sont également de faible puissance. Il faut donc répondre à un double objectif : l'efficacité d'une solution tout en offrant une bonne qualité d'image à la réception. La contribution de cette thèse porte principalement sur l'étude des méthodes de traitement et de compression d'images au noeud-caméra, nous avons proposé une nouvelle méthode de compression d'images qui permet d'améliorer l'efficacité énergétique des réseaux de capteurs sans fil. Des expérimentations sur une plate-forme réelle de réseau de capteurs d'images ont été réalisées afin de démontrer la validité de nos propositions, en mesurant des aspects telles que la quantité de mémoire requise pour l'implantation logicielle de nos algorithmes, leur consommation d'énergie et leur temps d'exécution. Nous présentons aussi, les résultats de synthèse de la chaine de compression proposée sur des systèmes à puce FPGA et ASIC / The increasing development of Wireless Camera Sensor Networks today allows a wide variety of applications with different objectives and constraints. However, the common problem of all the applications of sensor networks remains the vulnerability of sensors nodes because of their limitation in material resources, the most restricting being energy. Indeed, the available wireless technologies in this type of networks are usually a low-power, short-range wireless technology and low power hardware resources (CPU, battery). So we should meet a twofold objective: an efficient solution while delivering outstanding image quality on reception. This thesis concentrates mainly on the study and evaluation of compression methods dedicated to transmission over wireless camera sensor networks. We have suggested a new image compression method which decreases the energy consumption of sensors and thus maintains a long network lifetime. We evaluate its hardware implementation using experiments on real camera sensor platforms in order to show the validity of our propositions, by measuring aspects such as the quantity of memory required for the implantation program of our algorithms, the energy consumption and the execution time. We then focus on the study of the hardware features of our proposed method of synthesis of the compression circuit when implemented on a FPGA and ASIC chip prototype

Devido à sua importância em turbulência causada por ondas de deriva e à aplicação com propósitos em diagnósticos de plasma, a investigação de fluxos zonais (ZF) e modos acústicos geodésicos (GAM) tem atraído bastante atenção na literatura em física de plasmas. Nesta tese, primeiramente consideramos efeitos de equilíbrio com rotação poloidal e toroidal nestes modos, posteriormente investigamos efeitos diamagnéticos em GAM a partir de um modelo de dois fluido, no qual incluímos viscosidade paralela de íons e, na parte final, consideramos amortecimento de Landau e efeitos diamagnéticos simultaneamente no estudo de GAM, porém, a partir do modelo girocinético. Efeitos diamagnéticos são causados por termos que envolvem gradientes de densidade e de temperatura provenientes da função Maxwelliana de equilíbrio. O acoplamento entre os harmônicos poloidais, $m = \\pm1$, e as derivadas radiais de quantidades macroscópicas do plasma é responsável pelo aumento no valor da frequência no GAM de alta frequência e pela instabilidade no GAM de baixa frequência. Este tipo de instabilidade, que é proporcional à frequência diamagnética de elétrons e à razão entre os gradientes de temperatura e de densidade, é mais propenso a ocorrer em posições radiais em que o fator segurança é alto. Modos geodésicos são fracamente amortecidos devido a um mecânismo não colisional conhecido por amortecimento de Landau, o qual é causado pela interação entre a onda eletrostática e partículas carregadas, íons no caso, e a taxa de amortecimento é maior próximo ao centro da coluna de plasma, onde o fator de segurança assume valores mais baixos. O equilíbrio MHD com rotação foi investigado em três regimes com relação às superfícies magnéticas: isotérmico, adiabático e isométrico. Foi observado que o gradiente de temperatura possui sentido oposto em relação à velocidade de rotação poloidal apenas no regime isométrico. Ao considerar equilíbrio com rotação e superfícies magnéticas isotérmicas e incluir fluxo de calor na equação da energia, observamos que ZF apresentam frequência não-nula, a qual é proporcional à velocidade de rotação poloidal e inversamente proporcional ao fator de segurança. Como direções futuras ressaltamos que é importante considerar efeitos eletromagnéticos, estudar automodos geodésicos e incluir o efeito de partículas aprisionadas para o desenvolvimento da física de ZF e GAM. Tal desenvolvimento beneficiará tanto a área de transporte em tokamaks como a área de diagnósticos, na qual a obtenção do perfil radial da temperatura de íons e do fator de segurança é um dos objetivos. Nesta área, um novo tipo de diagnóstico conhecido como espectroscopia em modos acústicos geodésicos está sendo desenvolvido baseado no estudo de automodos. / Due to the important role in drift wave turbulence and applications for plasma diagnostic purposes, the investigation of zonal flows (ZF) and associated geodesic acoustic modes (GAM) has arisen much attention in the plasma physics literature. In this thesis, first we consider equilibrium poloidal and toroidal rotation effects on these modes using the ideal MHD model, then we investigate diamagnetic effects on GAM using a two fluid model that includes parallel ion viscosity, and, in the final step, we include both Landau damping and diamagnetic effects on the study of GAM within the framework of the gyrokinetic model. By diamagnetic effects we mean the density and temperature radial gradients terms coming from the equilibrium Maxwellian distribution function. The effects caused by the coupling between the $m = \\pm1$ poloidal harmonics and the radial derivatives of equilibrium macroscopic quantities are responsible for an increase in the frequency value of the high frequency GAM and for an instability in the low frequency GAM. This instability, which is proportional to the electron drift frequency and the ratio between ion temperature and density gradients, are more likely to occur in radial positions where the safety factor is high. We observe that geodesic modes are slowly damped by a collisionlees mechanism known as Landau damping which is caused by the wave particle interaction between the eletrostatic potential and the íons. This damping is enhanced near the center of the plasma column, where the safety factor has lower values. Equilibrium MHD with plasma rotation were investigated in three regimes regarding the magnetic surfaces: isotherm, adiabatic and isometric. It is found that the temperature gradient has opposite directions compared to the poloidal rotation only for the isometric regime. By considering equilibrium rotation with isotherm magnetic surfaces and including heat flux we observed that ZF has a non-zero frequency which is proportional to the poloidal velocity and the inverse of the safety factor. For future directions we point out that electromagnetic effects, geodesic eigenmodes and trapped particles physics should be important for the development of the ZF and GAM physics, either in the area of anomalous transport caused by drift wave turbulence or for diagnostic purposes for obtaining the radial profile of the ion temperature and the safety factor. In this area, a new kind of diagnostic known as geodesic acoustic mode spectroscopy is being developing based on the study of eigenmodes.

Face aux forts besoins de réduction de la consommation énergétique et de l’impact environnemental,le bâtiment d’aujourd’hui vise la performance en s’appuyant sur des sourcesd’énergie de plus en plus diversifiées (énergies renouvelables), une enveloppe mieux conçue(isolation) et des systèmes de gestion plus avancés. Plus la conception vise la basse consommation,plus les interactions entre ses composants sont complexes et peu intuitives. Seule unerégulation plus intégrée permettrait de prendre en compte cette complexité et d’optimiser lefonctionnement pour atteindre la basse consommation sans sacrifier le confort.Les techniques de commande prédictive, fondées sur l’utilisation de modèles dynamiqueset de techniques d’optimisation, promettent une réduction des consommations et de l’inconfort.Elles permettent en effet d’anticiper l’évolution des sources et des besoins intermittentstout en tirant parti de l’inertie thermique du bâtiment, de ses systèmes et autres élémentsde stockage. Cependant, dans le cas du bâtiment, l’obtention d’un modèle dynamique suffisammentprécis présente des difficultés du fait d’incertitudes importantes sur les paramètresdu modèle et les sollicitations du système. Les avancées récentes dans le domaine de l’instrumentationdomotique constituent une opportunité prometteuse pour la réduction de cesincertitudes, mais la conception d’un tel système pour une telle application n’est pas triviale.De fait, il devient nécessaire de pouvoir considérer les problématiques de monitoring énergétique,d’instrumentation, de commande prédictive et de modélisation de façon conjointe.Cette thèse vise à identifier les liens entre commande prédictive et instrumentation dansle bâtiment, en proposant puis exploitant une méthode générique de modélisation du bâtiment,de simulation thermique et de résolution de problèmes d’optimisation. Cette méthodologiemet en oeuvre une modélisation thermique multizone du bâtiment, et des algorithmesd’optimisation reposant sur un modèle adjoint et les outils du contrôle optimal. Elle a étéconcrétisée dans un outil de calcul permettant de mettre en place une stratégie de commandeprédictive comportant des phases de commande optimale, d’estimation d’état et decalibration.En premier lieu, nous étudions la formulation et la résolution d’un problème de commandeoptimale. Nous abordons les différences entre un tel contrôle et une stratégie de régulationclassique, entre autres sur la prise en compte d’indices de performance et de contraintes. Nousprésentons ensuite une méthode d’estimation d’état basée sur l’identification de gains thermiquesinternes inconnus. Cette méthode d’estimation est couplée au calcul de commandeoptimale pour former une stratégie de commande prédictive.Les valeurs des paramètres d’un modèle de bâtiment sont souvent très incertaines. Lacalibration paramétrique du modèle est incontournable pour réduire les erreurs de prédictionet garantir la performance d’une commande optimale. Nous appliquons alors notreméthodologie à une technique de calibration basée sur des mesures de températures in situ.Nous ouvrons ensuite sur des méthodes permettant d’orienter le choix des capteurs à utiliser(nombre, positionnement) et des paramètres à calibrer en exploitant les gradients calculéspar la méthode adjointe.La stratégie de commande prédictive a été mise en oeuvre sur un bâtiment expérimentalprès de Chambéry. Dans le cadre de cette étude, l’intégralité du bâtiment a été modélisé,et les différentes étapes de notre commande prédictive ont été ensuite déployées de mainière séquentielle. Cette mise en oeuvre permet d’étudier les enjeux et les difficultés liées àl’implémentation d’une commande prédictive sur un bâtiment réel.Cette thèse est issue d’une collaboration entre le CEA Leti, l’IFSTTAR de Nantes et leG2ELab, et s’inscrit dans le cadre du projet ANR PRECCISION. / More efficient energy management of buildings through the use of Model Predictive Control(MPC) techniques is a key issue to reduce the environmental impact of buildings. Buildingenergy performance is currently improved by using renewable energy sources, a betterdesign of the building envelope (insulation) and the use of advanced management systems.The more the design aims for high performance, the more interactions and coupling effectsbetween the building, its environment and the conditions of use are important and unintuitive.Only a more integrated regulation would take in account this complexity, and couldhelp to optimize the consumption without compromising the comfort.Model Predictive Control techniques, based on the use of dynamic models and optimizationmethods, promise a reduction of consumption and discomfort. They can generate energysavings by anticipating the evolution of renewable sources and intermittent needs, while takingadvantage of the building thermal inertia and other storage items. However, in the caseof buildings, obtaining a good dynamic model is tough, due to important uncertainties onmodel parameters and system solicitations.Recent advances in the field of wireless sensor networks are fostering the deployment ofsensors in buildings, and offer a promising opportunity to reduce these errors. Nevertheless,designing a sensor network dedicated to MPC is not obvious, and energy monitoring,instrumentation, modeling and predictive control matters must be considered jointly.This thesis aims at establishing the links between MPC and instrumentation needs inbuildings. We propose a generic method for building modeling, thermal simulation andoptimization. This methodology involves a multi-zone thermal model of the building, andefficient optimization algorithms using an adjoint model and tools from the optimal controltheory. It was implemented in a specific toolbox to develop a predictive control strategywith optimal control phases, state estimation phases and model calibration.At first, we study the formulation and resolution of an optimal control problem. We discussthe differences between such a control and a conventional regulation strategy, throughperformance indicators. Then, we present a state estimation method based on the identificationof unknown internal gains. This estimation method is subsequently coupled with theoptimal control method to form a predictive control strategy.As the parameters values of a building model are often very uncertain, parametric modelcalibration is essential to reduce prediction errors and to ensure the MPC performance. Consequently,we apply our methodology to a calibration technique based on in situ temperaturemeasurements. We also discuss how our approach can lead to selection techniques in orderto choose calibrated parameters and sensors for MPC purposes.Eventually, the predictive control strategy was implemented on an experimental building,at CEA INES, near Chambéry. The entire building was modeled, and the different steps ofthe control strategy were applied sequentially through an online supervisor. This experimentgave us a useful feedback on our methodology on a real case.This thesis is the result of a collaboration between CEA Leti, IFSTTAR Nantes andG2ELab, and is part of the ANR PRECCISION project.

Cette thèse considère quatre systèmes physiques complexes pour lesquels il est exceptionnellement possible d’identifier des variables lentes qui contrôlent l'évolution à temps long du système complet. La séparation d'échelle de temps entre ces variables lentes et les autres variables permet d'utiliser la technique de moyennisation stochastique pour obtenir une dynamique effective pour les variables lentes. Cette thèse considère la possibilité de prédire les événements rares dans le système solaire. Nous avons étudié deux types d’événements rares. Le premier est un renversement possible de l'axe de rotation de la Terre en l'absence des effets de marée de la Lune. Le second est la désintégration de l'ensemble du système solaire interne suite à une instabilité dans l'orbite de Mercure. Pour chacun des deux problèmes, il existe des variables lentes non triviales, qui ne sont pas données par des variables physiques naturelles. La moyennisation stochastique a permis de découvrir le mécanisme physique qui conduit à ces événements rares et de donner, par une approche purement théorique, l'ordre de grandeur de la probabilité de ces phénomènes. Nous avons également montré que la déstabilisation de Mercure sur un temps inférieur à l'âge du système solaire obéit à un mécanisme d'instanton bien décrit par la théorie des grandes déviations. Le travail effectué dans cette thèse ouvre donc un nouveau champ d'action pour l'utilisation d'algorithmes de calcul d'événements rares. Nous avons utilisé pour la première fois les théorèmes de moyennisation stochastique dans le cadre de la mécanique céleste pour quantifier l'effet stochastique des astéroïdes sur la trajectoire des planètes. Enfin, une partie du travail porte sur un problème de turbulence géophysique: dans l'atmosphère de Jupiter, on peut observer des structures zonales (jets) à grande échelles évoluant beaucoup plus lentement que les tourbillons environnants. Nous montrons qu'il est pour la première fois possible d'obtenir explicitement le profil de ces jets par moyennisation des degrés de liberté turbulents rapides. / The present thesis describes four complex dynamical systems. In each system, the long-term behavior is controlled by a few number of slow variables that can be clearly identified. We show that in the limit of a large timescale separation between the slow variables and the other variables, stochastic averaging can be performed and leads to an effective dynamics for the set of slow variables. This thesis also deals with rare events predictions in the solar system. We consider two possible rare events. The first one is a very large variation of the spin axis orientation of a Moonless Earth. The second one is the disintegration of the inner solar system because of an instability in Mercury’s orbit. Both systems are controlled by non-trivial slow variables that are not given by simple physical quantities. Stochastic averaging has led to the discovery of the mechanism leading to those rare events and gives theoretical bases to compute the rare events probabilities. We also show that Mercury’s short-term destabilizations (compared to the age of the solar system) follow an instanton mechanism, and can be predicted using large deviation theory. The special algorithms devoted to the computation of rare event probabilities can thus find surprising applications in the field of celestial mechanics. We have used for the first time stochastic averaging in the field of celestial mechanics to give a relevant orders of magnitude for the long-term perturbation of planetary orbits by asteroids. A part of the work is about geophysical fluid mechanics. In Jupiter atmosphere, large scale structures (jets) can be observed, the typical time of evolution of which is much larger than that of the surrounding turbulence. We show for the first time that the mean wind velocity can be obtained explicitly by averaging the fast turbulent degrees of freedom.

Devido à sua importância em turbulência causada por ondas de deriva e à aplicação com propósitos em diagnósticos de plasma, a investigação de fluxos zonais (ZF) e modos acústicos geodésicos (GAM) tem atraído bastante atenção na literatura em física de plasmas. Nesta tese, primeiramente consideramos efeitos de equilíbrio com rotação poloidal e toroidal nestes modos, posteriormente investigamos efeitos diamagnéticos em GAM a partir de um modelo de dois fluido, no qual incluímos viscosidade paralela de íons e, na parte final, consideramos amortecimento de Landau e efeitos diamagnéticos simultaneamente no estudo de GAM, porém, a partir do modelo girocinético. Efeitos diamagnéticos são causados por termos que envolvem gradientes de densidade e de temperatura provenientes da função Maxwelliana de equilíbrio. O acoplamento entre os harmônicos poloidais, $m = \\pm1$, e as derivadas radiais de quantidades macroscópicas do plasma é responsável pelo aumento no valor da frequência no GAM de alta frequência e pela instabilidade no GAM de baixa frequência. Este tipo de instabilidade, que é proporcional à frequência diamagnética de elétrons e à razão entre os gradientes de temperatura e de densidade, é mais propenso a ocorrer em posições radiais em que o fator segurança é alto. Modos geodésicos são fracamente amortecidos devido a um mecânismo não colisional conhecido por amortecimento de Landau, o qual é causado pela interação entre a onda eletrostática e partículas carregadas, íons no caso, e a taxa de amortecimento é maior próximo ao centro da coluna de plasma, onde o fator de segurança assume valores mais baixos. O equilíbrio MHD com rotação foi investigado em três regimes com relação às superfícies magnéticas: isotérmico, adiabático e isométrico. Foi observado que o gradiente de temperatura possui sentido oposto em relação à velocidade de rotação poloidal apenas no regime isométrico. Ao considerar equilíbrio com rotação e superfícies magnéticas isotérmicas e incluir fluxo de calor na equação da energia, observamos que ZF apresentam frequência não-nula, a qual é proporcional à velocidade de rotação poloidal e inversamente proporcional ao fator de segurança. Como direções futuras ressaltamos que é importante considerar efeitos eletromagnéticos, estudar automodos geodésicos e incluir o efeito de partículas aprisionadas para o desenvolvimento da física de ZF e GAM. Tal desenvolvimento beneficiará tanto a área de transporte em tokamaks como a área de diagnósticos, na qual a obtenção do perfil radial da temperatura de íons e do fator de segurança é um dos objetivos. Nesta área, um novo tipo de diagnóstico conhecido como espectroscopia em modos acústicos geodésicos está sendo desenvolvido baseado no estudo de automodos. / Due to the important role in drift wave turbulence and applications for plasma diagnostic purposes, the investigation of zonal flows (ZF) and associated geodesic acoustic modes (GAM) has arisen much attention in the plasma physics literature. In this thesis, first we consider equilibrium poloidal and toroidal rotation effects on these modes using the ideal MHD model, then we investigate diamagnetic effects on GAM using a two fluid model that includes parallel ion viscosity, and, in the final step, we include both Landau damping and diamagnetic effects on the study of GAM within the framework of the gyrokinetic model. By diamagnetic effects we mean the density and temperature radial gradients terms coming from the equilibrium Maxwellian distribution function. The effects caused by the coupling between the $m = \\pm1$ poloidal harmonics and the radial derivatives of equilibrium macroscopic quantities are responsible for an increase in the frequency value of the high frequency GAM and for an instability in the low frequency GAM. This instability, which is proportional to the electron drift frequency and the ratio between ion temperature and density gradients, are more likely to occur in radial positions where the safety factor is high. We observe that geodesic modes are slowly damped by a collisionlees mechanism known as Landau damping which is caused by the wave particle interaction between the eletrostatic potential and the íons. This damping is enhanced near the center of the plasma column, where the safety factor has lower values. Equilibrium MHD with plasma rotation were investigated in three regimes regarding the magnetic surfaces: isotherm, adiabatic and isometric. It is found that the temperature gradient has opposite directions compared to the poloidal rotation only for the isometric regime. By considering equilibrium rotation with isotherm magnetic surfaces and including heat flux we observed that ZF has a non-zero frequency which is proportional to the poloidal velocity and the inverse of the safety factor. For future directions we point out that electromagnetic effects, geodesic eigenmodes and trapped particles physics should be important for the development of the ZF and GAM physics, either in the area of anomalous transport caused by drift wave turbulence or for diagnostic purposes for obtaining the radial profile of the ion temperature and the safety factor. In this area, a new kind of diagnostic known as geodesic acoustic mode spectroscopy is being developing based on the study of eigenmodes.

Le stockage d’énergie par air comprimé est une des technologies nécessaires à l’emploi massif des énergies renouvelables intermittentes, d’origine solaire ou éolienne. La compression d’air par piston liquide permet d’augmenter l’efficacité du stockage d’énergie en favorisant un échange thermique intense dans la chambre de compression. La description et l’évaluation de cet échange convectif pour des chambres de compression à faible rapport alésage/course ne sont cependant que peu étudiées dans la littérature scientifique. A l’aide d’une étude expérimentale menée sur deux bancs d’essais, l’échange convectif interne dans la chambre de compression est étudié. Une méthode inverse, couplée à la mesure de la température de l’air comprimé et de la position du piston, est employée afin de déterminer les transferts thermiques pariétaux instantanés au cours des compressions.Après avoir mis en lumière la présence systématique d’une transition du régime convectif de type laminaire vers un régime turbulent dans le volume d’air comprimé, de nouvelles corrélations d’échange convectif sont recherchées. Sur la base de 73 expérimentations, plusieurs formes de corrélations basées sur des nombres sans dimension sont optimisées puis comparées. Deux nouvelles corrélations du nombre de Nusselt, l’une en régime laminaire et l’autre en régime turbulent, sont ensuite sélectionnées. Un modèle instationnaire thermodynamique 1D de la chambre de compression est alors construit dans l’environnement Matlab / Simulink afin de tester la qualité de ces corrélations. Les résultats numériques sont ainsi comparés aux données expérimentales. Finalement, deux essais expérimentaux supplémentaires, réalisés sur un banc d’essai différent, permettent de confirmer la qualité des nouvelles corrélations d’échange convectif proposées. / Energy storage by compressed air would be one of the required technologies for enabling massive use of intermittent solar or wind renewable energy sources. Air compression using a liquid piston enables an increase in the energy storage efficiency by inducing an intense heat exchange in the compression chamber. Few studies reported in the literature have focused on the description and evaluation of the convective heat exchange for a low ratio compression chamber (L/D). Using an experimental study and two test benches, the internal convective heat transfer during compression has been studied. In addition to measuring liquid piston position and air pressure, an inverse method was used to determine the instantaneous parietal convective heat flow during compression. After highlighting the presence of a systematic transition from laminar to turbulent convective regime in the compressed air, new convective heat transfer correlations were sought. On the basis of 73 experiments, several correlation forms based on dimensionless numbers were optimized and compared. Two new Nusselt number correlations, one for laminar and the other for turbulent flow, were then selected. A 1D thermodynamic transient model of the compression chamber was built using Matlab / Simulink environment in order to test the quality of these correlations. Thus, numerical results and experimental data were compared. Finally, results from two additional experiments carried out on a different test bench have confirmed the quality of the new proposed correlations for convective heat exchange.