No description available.

The transport of solar energetic particles (SEPs) in the inner heliosphere is a very important issue which can affect our daily life. For example, large SEP events can lead to the failure of power grids, interrupt communications, and may participate in global climate change. The SEPS also can harm humans in space and destroy the instruments on board spacecraft. Studying the transport of SEPs also helps us understand remote regions of space which are not visible to us because there are not enough photons in those places.The interplanetary magnetic field is the medium in which solar energetic particles travel. The Parker Model of the solar wind and its successor, the Weber and Davis model, have been the dominant models of the solar wind and the interplanetary magnetic field since 1960s. In this thesis, I have reviewed these models and applied an important correction to the Weber and Davis model. Various solar wind models and their limitations are presented. Different models can affect the calculation of magnetic field direction at 1~AU by as much as about 30\%.Analysis of the onset of SEP events could be used to infer the release time of solar energetic particles and to differentiate between models of particle acceleration near the Sun. It is demonstrated that because of the nature of the stochastic heliospheric magnetic field, the path length measured along the lineof force can be shorter than that of the nominal Parker spiral. These results help to explain recent observations.A two dimensional model and a fully three dimensional numerical model for the transport of SEPs has been developed based on Parker's transport equation for the first time. ``Reservoir'' phenomenon, which means the inner heliosphere works like a reservoir for SEPs during large SEP events, and multi-spacecraft observation of peak intensities are explained by this numerical model.

Electromagnetic Ion Cyclotron (EMIC) waves are believed to play an important role in the dynamics of energetic particles (both electrons and ions) trapped by the Earths magnetic field causing them to precipitate into the ionosphere via resonant interaction. In order to incorporate the EMIC-related loss processes into global magnetospheric models one needs to know solar wind and magnetospheric conditions favourable for EMIC wave excitation as well as the localization of the waves in the magnetosphere. EMIC waves are generated by anisotropic (Tperp/Tpara > 1) ion distributions. Generally, any process that leads to the formation of such distributions may be responsible for EMIC wave initiation. This thesis discusses magnetospheric compression as a new principal source of EMIC wave generation in the inner dayside magnetosphere. First, using ground-based and satellite instrumentation, it is shown that EMIC waves are often generated in the inner dayside magnetosphere during periods of enhanced solar wind dynamic pressure and associated dayside magnetospheric compression. The compression-related EMIC wave activity usually lasts for several hours while the magnetosphere remains compressed. Also, it is demonstrated that EMIC waves are generated in radially narrow (1 Re wide) region of high plasma density, just inside the plasmapause. Test particle simulations of energetic ion dynamics performed for this study confirmed that anisotropic ion distributions are generated in the compressed dayside magnetosphere, the temperature anisotropy being dependant on the strength of magnetospheric compression. It is found that in the inner magnetosphere these anisotropic particle distributions are formed due to particle drift shell-splitting in an asymmetric magnetic field. Finally, the generation of EMIC waves was studied self-consistently using a hybrid particle-in-cell code in order to determine whether the degree of anisotropy estimated from the test particle simulations is sufficient to produce EMIC waves like those detected and to explain some of the observed wave properties.

No description available.

The interaction between the solar wind and the partially ionized gas of the local interstellar medium (ISM) creates a bubble known as the heliosphere. Classically, the shape of the heliosphere has been regarded as comet-like, with a long tail pointed in the direction opposite the Sun’s motion through the ISM. In this view, the solar magnetic field was assumed to have a negligible effect on the global structure of the heliosphere. Recent advances in numerical modeling have revealed the importance of the solar magnetic field in its ability to confine and collimate the solar wind plasma, and the shape of the heliosphere has been called into question. Energetic neutral atoms (ENAs) are created throughout the heliosphere via charge exchange. The separate contributions of the solar magnetic field topology and the solar wind structure to ENA observations is largely unexplored. The Interstellar Boundary Explorer (IBEX) has been providing a global perspective of the heliosphere through ENA maps with energies ranging from 0.2 to 6 keV. In this dissertation, three-dimensional magnetohydrodynamic simulations of the heliosphere are used as input to an ENA model designed to produce synthetic ENA maps. I compare modeled ENA maps with IBEX observations to investigate how different heliospheric conditions and properties affect ENAs created in the heliosphere, and therefore how ENA observations can be used to understand the heliosphere. First, I investigate the effect of the solar wind collimation by the solar magnetic field on ENA maps in the case of a solar wind without latitudinal variation. I find that even in the absence of variations of the solar wind, two lobes of strong ENA flux form at high latitudes, similar to what is observed by IBEX at high energies. Second, I test the effect of a latitudinally-varying solar wind on ENAs both with and without the inclusion of the solar magnetic field. I show that the latitudinal variations of the solar wind during solar minimum creates a structured ENA profile with latitude, corresponding to the profile observed at 1 AU, but that the solar magnetic field significantly enhances ENA flux in the region where the solar wind is confined. Lastly, I investigate the effect of the solar cycle on ENAs and how changing solar wind conditions (e.g. density, temperature, velocity) affect the heliosphere over time. I demonstrate that, given changes in the solar cycle, there is a significant evolution in the modeled ENA flux due to the changes in the solar wind profile and the solar magnetic field, which is also seen by ENA observations.

Yes / A web-based prototype system for predicting solar energetic particle (SEP) events and solar flares for use by space launch operators is presented. The system has been developed as a result of the European Space Agency (ESA) project SEPsFLAREs (Solar Events Prediction system For space LAunch Risk Estimation). The system consists of several modules covering the prediction of solar flares and early SEP Warnings (labeled Warning tool), the prediction of SEP event occurrence and onset, and the prediction of SEP event peak and duration. In addition, the system acquires data for solar flare nowcasting from Global Navigation Satellite Systems (GNSS)-based techniques (GNSS Solar Flare Detector, GSFLAD and the Sunlit Ionosphere Sudden Total Electron Content Enhancement Detector, SISTED) as additional independent products that may also prove useful for space launch operators. / This work has been developed in the frame of 34 SEPsFLAREs project (ESA Contract Number 4000109626/13/NL/ 35 AK), which is an activity funded by ESA/ESTEC Space Environ- 36 ment (TEC-EES) section. The authors of this work are grateful to 37 ESA’s MONITOR project (Contract Number 4000100988/2010/F/ 38 WE) for allowing the use of GSFLAD and SISTED products. 39 We also thank AGAUR (Generalitat de Catalunya) for the financial 40 support from Grant PDJ 2014 00074.

Turbulent magnetic fields are ubiquitous in space physics and astrophysics. The influence of magnetic turbulence on the motions of charged particles contains the essential physics of the transport and acceleration of energetic charged particles in the heliosphere, which is to be explored in this thesis. After a brief introduction on the energetic charged particles and magnetic fields in the heliosphere, the rest of this dissertation focuses on three specific topics: 1. the transport of energetic charged particles in the inner heliosphere, 2. the acceleration of ions at collisionless shocks, and 3. the acceleration of electrons at collisionless shocks. We utilize various numerical techniques to study these topics. In Chapter 2 we study the propagation of charged particles in turbulent magnetic fields similar to the propagation of solar energetic particles in the inner heliosphere. The trajectories of energetic charged particles in the turbulent magnetic field are numerically integrated. The turbulence model includes a Kolmogorov-like magnetic field power spectrum containing a broad range of scales from those that lead to large-scale field-line random walk to small scales leading to resonant pitch-angle scattering of energetic particles. We show that small-scale variations in particle intensities (the so-called "dropouts") and velocity dispersions observed by spacecraft can be reproduced using this method. Our study gives a new constraint on the error of "onset analysis", which is a technique commonly used to infer information about the initial release of energetic particles. We also find that the dropouts are rarely produced in the simulations using the so-called "two-component" magnetic turbulence model (Matthaeus et al., 1990). The result questions the validity of this model in studying particle transport. In the first part of Chapter 3 we study the acceleration of ions in the existence of turbulent magnetic fields. We use 3-D self-consistent hybrid simulations (kinetic ions and fluid electrons) to investigate the acceleration of low-energy particles (often termed as "injection problem") at parallel shocks. We find that the accelerated particles always gain the first amount of energy by reflection and acceleration at the shock layer. The protons can move off their original field lines in the 3-D electric and magnetic fields. The results are consistent with the acceleration mechanism found in previous 1-D and 2-D simulations. In the second part of Chapter 3, we use a stochastic integration method to study diffusive shock acceleration in the existence of large-scale magnetic variations. We show that the 1-D steady state solution of diffusive shock acceleration can be significantly modified in this situation. The results suggest that the observations of anomalous cosmic rays by Voyager spacecraft can be explained by a 2-D shock that includes the large-scale magnetic field variations. In Chapter 4 we study electron acceleration at a shock passing into a turbulent magnetic field by using a combination of hybrid simulations and test-particle electron simulations. We find that the acceleration of electrons is greatly enhanced by including the effect of large-scale magnetic turbulence. Since the electrons mainly follow along the magnetic lines of force, the large-scale braiding of field lines in space allows the fast-moving electrons interacting with the shock front multiple times. Ripples in the shock front occurring at various scales also contribute to the acceleration by mirroring the electrons. Our calculation shows that this process favors electron acceleration at perpendicular shocks. We discuss the application of this process in interplanetary shocks and flare termination shocks. We also discuss the implication of this study to solar energetic particles (SEPs) by comparing the acceleration of electrons with that of protons. The intensity correlation of electrons and ions in SEP events indicates that perpendicular or quasi-perpendicular shocks play an important role in accelerating charged particles. In Chapter 5 we summarize the results of this thesis and discuss possible future work.

La faisabilite de la fusion magnetique est dependante de notre capacite a confiner l'energie des particules supra-thermiques liberees a haute energie par les reactions de fusion, dans les meilleures conditions de securite et d'efficacite. Dans ce but, il est necessaire de comprendre l'interaction entre les particules energetiques et le plasma thermo-nucleaire qui constitue l'environnement des reactions de fusion, afin de la controler. La these que nous presentons ici s'inscrit dans cet effort. Le coeur du travail mene est l'etude d'un type d'instabilite, le Beta Alfven Eigenmode (BAE), que peuvent exciter les particules energetiques, et dont on peut craindre qu'il degrade fortement non seulement le confinement des particules energetiques mais aussi le confinement du plasma dans sa globalite. Dans un premier temps, nous nous attacherons a decrire les caracteristiques de ce mode et nous deriverons sa relation de dispersion ainsi que sa structure. Dans une seconde partie, nous effectuerons l'etude de la stabilite lineaire de ce mode en presence de particules energetiques. Cette etude nous a permis de definir un critere analytique rendant compte de la capacite des particules energetiques a exciter le BAE. Ce critere sera discute et confronte aux resultats d'experiences menees durant la these. Cette etude lineaire presentant cependant quelques limites, il nous est apparu important de nous poser la question de la possibilite d'une modication de la stabilite du BAE liee a l'utilisation d'une description non-lineaire. Nous suggererons dans cette presentation un processus, verifie analytiquement et numeriquement, dont peut resulter l'existence d'etats meta-stables pour le BAE.

No description available.

In this thesis we examine the generation mechanisms of Pc 5 ULF waves during geomagnetic storms. Also, we study the interaction between Pc 5 ULF waves and energetic particles in the radiation belts and the observed energetic particle flux modulation by Pc 5 ULF waves is verified using particle simulations. Firstly, we present case studies of Pc 5 pulsations using ground-based magnetometer and satellite data during geomagnetic storm times, specifically we selecting three storm time events which show a brief increase in Dst in the main phase of the storms. By studying these events, we attempt to identify the generation mechanisms responsible for the geomagnetic pulsations. The observed pulsations exhibit the characteristic features of a Field Line Resonance. Our results also show evidence for the penetration of ULF wave power in the Pc 5 band to much lower L-shells than normal, suggesting significant reduction of the local Alfven eigenfrequency continuum as compared to non-storm times. This may have considerable significance for the interaction between ULF waves and MeV electrons in the outer radiation belt during storms. Secondly, based on the hypothesis that Pc 5 ULF waves may play an important role in energetic particle dynamics in the radiation belt and ring current, we investigated the relationship between Pc 5 pulsations and energetic particle flux oscillations. We observed very strong Pc 5 oscillations during the great magnetic storm of March 24, 1991 [Lee et al., 2007] and electron flux simultaneously oscillating with the same frequencies in the time domain. We also characterize two more events and present an examination of the relationship between the electron flux modulation and Pc 5 ULF pulsations. Based on our observations, the modulation of energetic particles might be associated with a drift-resonance interaction, or the advection of an energetic particle density gradient. Finally, we numerically calculate the trajectories and energy change of charged particles under the influence of model ULF wave electric fields. This modeling work is used to help to explain the observations and provides evidence which supports the modulation mechanisms such as advection of a flux gradient and drift resonance.