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In the three preceding papers in the series, we presented a model dealing with the global and small-scale structure and kinematics of hierarchically assembled, virialised, collisionless systems, which correctly accounted for the typical properties of simulated cold darkmatter (CDM) haloes. This model relied, however, on the spherical symmetry assumption. Here we show that the foundations of the model hold equally well for triaxial systems and extend it in a fully accurate way to objects that satisfy the latter more general symmetry. The master equations in the new version take the same form as in the version for spherically symmetric objects, but the profiles of all the physical quantities are replaced by their respective spherical averages. All the consequences of the model drawn under the spherical symmetry assumption continue to hold. In addition, the new version allows one to infer the axial ratios of virialised ellipsoids from those of the corresponding protoobjects. The present results generalise and validate those obtained in Papers I, II and III for CDM haloes. In particular, they confirm that all halo properties are the natural consequence of haloes evolving through accretion and major mergers from triaxial peaks (secondary maxima) in the primordial density field.

onospheric scintillation consists on rapid fluctuations in the amplitude and phase of electromagnetic signals, which includes those of the Global Navigation Satellite System (GNSS), that can lead to cycle slips and even to a loss of lock on the receiver tracking. Hence, scintillation has become one of the major concerns in navigation and the detection and/or mitigation of its effects is one of the current challenges in achieving precise GNSS navigation. This study is focused in characterizing the ionospheric scintillation phenomenon mainly at high latitudes, although one mid-latitude and one low-latitude station have been included in order to compare the results obtained and to be able to correlate the Total Electron Content (TEC) fluctuations with phase scintillation at all latitudes. This characterization has been done based on the parameters σϕ, ROT IL1 and ROT ILGF , using a database of two years of data, 2014 and 2015, and dividing each of them into three different periods (January to April, May to August, and September to December) in order to better assess the levels of scintillation at each station of the year. Moreover, the results obtained using the signals from two different GNSS satellite constellations (GPS and GLONASS) have been studied and compared. The thresholds for moderate and intense scintillation have been computed from the Cumulative Distribution Functions (CDF) of each scintillation for each station, year, period of the year and GNSS satellite constellation using each parameter at 99% and 99.9% percentiles for moderate and intense levels of scintillation, respectively. Thus, using these thresholds and also using the 1-CDF plots, the seasonal evolution of parameters σϕ and ROT IL1 has been analyzed for different stations per constellation. Furthermore, the correlation between both ROT I parameters and σϕ has been assessed for each station, constellation, year and period of the year. It has been observed that these correlation indexes highly depend on the model of the receiver, location of the receiver and the type of constellation used, fact that will help to differentiate between the level of scintillation measured for different receivers per constellation. The scintillation phenomenon has been observed to depend on: the location of the receiver, period of the year, model of the receiver, GNSS satellite constellation, and obviously the ionosphere behaviour. Finally, the parameter ROT IL1 has been observed to perform better than ROT ILGF at high-latitude stations.

As the world becomes more complex rapidly having a smart infrastructure is a necessity to be able to manage them remotely by high accuracy. In order to cope with this issue we need to have precise navigation globally which could be challenging in high- and low latitudes then the focus here is on six GNSS (Global Navigation Satellite System) receivers in the arctic region (high latitude) with GLONASS and GPS constellations. The impact of ionospheric scintillation has been characterized based on Sigma Phi, AATR and ROTI, using a database of one year of data in 2014. The thresholds from cumulative distribution function (CDF) of those scintillation parameters at 99% and 99.9% for each station per constellation have been extracted and high scintillation events were detected. The 1-CDF plots of December and July were compared and the seasonal Sigma Phi evolution has been analyzed for different stations per constellation. Moreover the linear correlation between ROTI and Sigma Phi was observed. These correlation indexes highly depend on type of the receiver, location of the receiver and the type of constellation used which will help us to differentiate between the level or impact of scintillation measured for different receivers per constellation. The scintillation events are observed to depend generally on the location of the receiver, period of the day, performance of the receiver, satellite constellation, and ionosphere behaviour. In addition, the impact of data loss in the database analysed has been shown to be relevant and different from station to station. Finally, single frequency PPP could have a higher convergence time in comparison with double frequency PPP according to a preliminary study. Hence, a detailed future work to investigate this issue is proposed.

The research of this dissertation is studying the ionosphere by GPS radio occultation (RO) techniques. It is mainly divided into two parts. The first part focuses on the methodology in electron density profile retrievals from RO measurements. It aims to get more precise profiles from measured data. Classic Abel inversion is a methodology widely used in RO retrievals, and the error introduced by the spherical symmetry assumption is also well recognised. Separability Method (SM) was developed to eliminate this error in previous studies. In this work, the improvement brought by SM corresponding to classic method is checked and validated. The SM does have better performance excluding the Lack of Collocation (LoC) error. The precision of the results is also shown to depend on the accuracy of the supported GIMs, i.e., the more accurate GIMs are used, the better results can be obtained. The error in SM, introduced by the mis-modelling of using the Vertical Total Electron Content (VTEC) instead of ECLEO, the electron content below LEO height, is also checked. The result shows that it has only minor impact on the retrievals. The second part is the climatological study of topside ionosphere/bottomside plasmasphere based on the RO retrievals using SM, and aims to give a general picture of characteristics and features of these two regions in different solar periods, 2007 -- solar minimum, and 2014 – solar maximum. The empirical two-components models of topside profiles, STIP model and CPDH model, used to separate the ionospheric and plasmaspheric contribution to the VTEC measured from ground to global positioning system (GPS) satellite altitudes, are studied and validated. The conditions of applicability of the STIP model are also discussed. The same as other existing empirical models, it shows the picture of topside ionosphere till some limited altitude, which is decided by the Low Earth Orbit (LEO) satellite height used to observe the RO. The model is used to derive transition height hu and scale height hs during these two years. Generally, hu and hs show the clear diurnal, seasonal, solar cycle dependencies. The concept of IONf, the ionospheric fractional contribution to VTEC, is introduced and studied. The ionospheric features are shown and most of the ionospheric anomalies have been analyzed through this quantity. Compared to the other ionospheric related parameters, such as Ecion and Ecpl, electron content of ionosphere and plasmasphere, IONf is more stable. Hence, it is more suitable for ionosphere modelling. The Capacitor Model is used to model the consistent ‘ionospheric charging process’ during the period of the day between sunrise and midday/afternoon. The model shows a good performance to reproduce real data in different circumstances and for the maximum and minimum solar activity years analyzed. La recerca feta en aquesta dissertació consisteix en l'estudi de la ionosfera mitjançant tècniques d'Ocultació Ràdio (RO) de GPS. La primera part s'enfoca en la metodologia d'extracció de perfils de les mesures RO. L'objectiu és l'obtenció de perfils més precisos mesurats a partir de les dades. La inversió clàssica d'Abel és una metodologia emprada àmpliament en l'obtenció de RO, tant mateix l'error introduït per l'assumpció de simetria també és reconegut. En ordre d'eliminar aquest error en estudis previs el Separability Method (SM) va ser desenvolupat. En el present treball es revisa i es valida la millora en el mètode clàssic aportada per SM. SM té un millor comportament inclús quan s'exclou l'error de Lack of Collocation (CoL). La precisió dels resultats depenen també de l'exactitud del GIM's suportats (p.ex. Com més exacte són els GIM's emprats millor són els resultats obtinguts). L'error de SM introduït pel modelatge incorrecte en utilitzar el Vertical Total Electron Content (VTEC) en lloc del ECLEO (el contingut d'electrons per sota de l'altura LEO) també és revisat. Els resultats mostren que només tenen un impacte mínim en les mesures extretes de RO. La segona part és un estudi de la climatologia de la part superior de la ionosfera I la part inferior de la plasmaesfera basat en l'extracció RO mitjançant SM amb l'objectiu de donar una imatge general de les característiques I tres d'aquestes dues regions en diferents períodes solars; el mínim solar de 2007 i el màxim solar de 2014. Dos models empírics bi-component, el model STIP i el model CPD, utilitzats per separar la contribució de la ionosfera i la plasmaesfera al VTEC, s?han estudiat i validat. Addicionalment també es discuteix sobre les condicions de l'aplicació de STIP. També es fa el mateix amb altres models empírics. Es mostra la imatge de la part superior de la ionosfera fins a un límit definit d'altitud el qual és determinat per l'altitud de satèl·lit Low Earth Orbit (LEO) que s?ha utilitzat per observar les RO. S'utilitza el model per derivar les transicions d'altitud hu I l'escala d'altitud hs durant aquests dos anys. Generalment, hu i hs mostren clarament dependències cícliques diürnals, estacionals i solars. És introduït i estudiat el concepte d'IONf, la fracció de contribució de la ionosfera al VTEC. Es mostren els atributs ionosfèrics i la majoria d'anomalies ionosfèriques es veuen plasmaesfera a través d'aquest mesura. En comparació amb altres paràmetres ionosfèrics, com ara Ecion i Ecpl, el contingut d'electrons de la ionosfera i la plasmaesfera IONf, és més estable. Degut això és més idoni pel modelatge de la ionosfera. El Model del Capacitador és emprat per modelar congruentment el procés de càrrega ionosfèrica' durant el sector de l'alba fins al migdia, mostrant que el model representa de manera bastant fidedigna les dades reals en diferents circumstàncies i durant els periodes de màxima i mínima activitat solar

Ground Based Augmentation System (GBAS) is a version of Differential Global Positioning System (DGPS) designed to reliably support airplane's all phase of approach, landing, departure and surface operations. Local ionospheric gradients are major threats to the GBAS, which prevents the advanced use of GBAS. A new monitor for detecting anomalous ionosphere to provide integrity assurance is implemented in this thesis. The monitor is based on the "Fast Initial Response" Cumulative Sum (FIR-CUSUM) quality-assurance method, which is sensitive to the small persistent shifts.

In this project, the study of a methodology for the computation of a reliable estimation sigma_pr_gnd is study. The method presented is intended to be used for the calibration of the GBAS station, using only one day of data. The GBAS station is used for aircraft navigation in the vicinity of an airport, being used for the precision approaches and landing of the aircraft.