This study uses high precision silicon isotopic measurements to understand events that occurred during the earliest stages of formation of the terrestrial planets. The isotopic compositions of diverse materials such as chondrites, lunar rocks and asteroidal basalts can shed light on the homogeneity of the solar nebula, metal-silicate differentiation on planetary bodies, and terrestrial moon formation. Limited variation in the Si isotopic composition of meteorites is evidence for a relatively homogeneous inner solar system with respect to silicon isotopes. The Si isotopic composition of bulk silicate Earth (BSE) is, however, heavier than meteorites. This points to an event unique to Earth that fractionated Si isotopes, such as core formation at terrestrial conditions. The Δ³⁰Si_{BSE-meteorite} value from this study indicates that the Earth’s core contains 8.7 (+8.1/−6.2) wt% Si. No systematic δ³⁰Si differences were found between any of the lunar lithologies analysed, implying a Si isotopic homogeneity of the sampled lunar source regions. The lunar average, δ³⁰Si = −0.29±0.08permil (2σ_SD), is identical to the recent value of Savage et al. (2010) for BSE of δ³⁰Si = −0.29 ± 0.08permil (2σ_SD). The best explanation of the data is that Si isotopes must have homogenised in the aftermath of the Moon-forming impact with no subsequent fractionation in the proto-lunar disk. The Si isotopic composition of olivine within lunar basalts was found to be the same or heavier than δ³⁰Si(pyroxene). This is not consistent with terrestrial data where δ³⁰Si(pyroxene) is always lighter than δ³⁰Si(olivine). Crystallisation history cannot explain the data, and the slow diffusion rates of Si rule out cooling rates as a cause. Therefore, it appears that inter-mineral fractionation of Si isotopes occurs differently on the Moon. The δ³⁰Si of chondrules picked from Allende spanned a range of ~0.6permil, a factor of two greater than the bulk meteorite range. There is no evidence for the variable δ30Si of the chondrules being the result of post-formation alteration and there is no convincing evidence for precursor heterogeneity being the primary cause. It is likely that Si isotopic composition of chondrules is the result of evaporation and reequilibration with the evaporated phase.

Satellite communication and navigation applications suffer due to space weather phenomena. The effects are particularly pronounced in the equatorial regions, which are highly ionised and more easily susceptible to space weather effects than the mid latitude regions. Nevertheless, the bulk of the research on TEC profile and behaviour has been carried out with respect to mid-latitude regions. The contribution of the Upper Plasmasphere (the altitudes above semisynchronous orbit height up to the Plasmapause height) to the Total Electron Content at any given location has been and continues to be an un-quantified component. The PEACE instrument in the Chinese – European Space Agency Double Star TC1 satellite and its highly eccentric equatorial orbit provides an excellent opportunity to build Upper Plasmaspheric Electron Content (UPEC) components in the Equatorial region from empirical in-situ measurements of electron density along the orbit in the 20000km to 40000km altitude range. This work develops and presents a methodology for deriving Plasmaspheric Electron Content from In-Situ, empirical electron density measurements in highly eccentric, elongated equatorial orbits, using the data from the Double Star TC1 satellite. As such this thesis also generates a database of Upper Plasmaspheric Electron Content (UPEC) along the orbital path of the TC1. This work also proposes a dedicated mission to be launched with highly eccentric orbits to generate a comprehensive equatorial TEC database based on this methodology. This works envisions that future mission to be preferably launched in the equatorial belt, thus providing the opportunity to develop an archive of data as well as a real time source for better understanding of the Appleton anomaly Effects on Plasmaspheric Electron Content.

A geomagnetic storm is triggered in response to a disturbance in the solar wind. The earth's ring current gets energized during a geomagnetic storm, which leads to a decrease in the horizontal component of the geomagnetic field on the earth's surface. The Disturbance Storm Time (Dst) index, which is a measure of the intensity of the ring current, is calculated by taking the average of this decrease in the horizontal intensity across four low latitude magnetometer stations and removing the quiet time secular variations. The rate of decrease of the Dst index is an indicator of the deenergization of the ring current particles. But there are several issues with the Dst measurement as a proxy of the ring current energy. In particular, the percentage contribution of the tail current effect to the Dst index is still debated. In this work, an effort has been made to separate and quantify the possible contribution of the tail current to the Dst index. The relative contribution for a selected set of storms for which the interplanetary magnetic field turned northward abruptly after the peak in Dst was observed is estimated. The WINDMI model of the nightside magnetosphere is used to investigate the contributions of ring current, magnetotail current, and magnetopause current on the observed two-phase decay of the Dst index. The role of different solar wind magnetosphere coupling functions on the Dst index calculated by the WINDMI model is also investigated. The performance of four other coupling functions in addition to the rectified vBs is evaluated. These coupling functions emphasize different physical mechanisms to explain the energy transfer into the magnetosphere due to solar wind velocity, dynamic pressure, magnetic field, and Mach number. One coupling function is due to Siscoe, another by Borovsky, and two by Newell. The results indicate that for a majority of cases, at most only vx, By, and Bz are needed to sufficiently account for the supply of energy to the ring current and geotail current components that contribute to the Dst index. The capabilities of the WINDMI model to reliably determine the state of the global magnetosphere are improved by employing the the Magnetotail (MT) index as a measurement constraint during large geomagnetic storms. The MT index is used as a proxy for the strength of the magnetotail current in the magnetosphere. The inclusion of the MT index as an optimization constraint in turn increases our confidence that the ring current contribution to the Dst index calculated by the WINDMI model is correct during large geomagnetic storms. To improve the models prediction of AL index, we also modify the ionospheric conductivity and fit to two substorms. The rate of reduction of convection in the magnetotail for some of these storms is numerically simulated by using inner magnetospheric models like the Fok Ring Current (FRC) and the Rice Convection Model along with the global BATSRUS model at the community coordinated modeling center. Model results are compared against magnetometer data by creating movie maps from several low-latitude magnetometer stations. The results indicate the contribution from the tail current to the Dst is important. In addition, the reduction of the cross-tail current during substorm dipolarization is predicted by the measured isotropic boundary locations. Several well known phenomena are identified in the magnetometer movie maps.

Das Magnetfeld der Erde wird durch Konvektionsströmungen im elektrisch leitfähigen, flüssigen eisenreichen äußeren Erdkern erzeugt. Eine drastische Ausprägung der dynamischen Prozesse im äußeren Erdkern sind sowohl Polaritätswechsel über geologische Zeiträume, als auch geomagnetische Feldexkursionen (kurze Umpolungen). Letztere sind in geologischen Archiven häufig unzureichend dokumentiert. Für ein verbessertes Verständnis über die Entwicklung des Erdmagnetfeldes in geologischer Vergangenheit benötigen wir Informationen über die Geometrie des gesamten Vektorfeldes, wofür neben der Bestimmung der Feldrichtungen auch die Bestimmung der absoluten Paläointensität und des Alters notwendig ist. Insbesondere Vulkanite bieten die Möglichkeit, Daten über die Richtung und vor allem auch die Intensität des Erdmagnetfeldes zur Zeit ihrer Platznahme zu gewinnen. Bisweilen ist eine genaue Charakterisierung der Entwicklung des Erdmagnetfeldes in Zeit und Raum schwer möglich, was sich in erster Linie auf den generellen Mangel an Paläointensitätsdaten zurückführen lässt. Ein Grund hierfür ist, dass die meisten Methoden zur absoluten Paläointensitätsbestimmung, auf Modifikationen der Thellier Methode basieren, welche nur auf magnetische Minerale im Einbereichs-Domänenzustand anwendbar ist und zudem hohe Ausschussraten liefert. Eine alternative Methode zur Bestimmung der absoluten Paläointensität ist die kürzlich entwickelte „multispecimen parallel differential pTRM“ (MS) Methode, welche im Vergleich zur Thellier Methode den Vorteil hat, dass sie theoretisch unabhängig ist vom Domänenzustand der magnetischen Minerale und somit auf alle Vulkanite anwendbar ist. Ein Schwerpunkt dieser Arbeit lag darauf, neue Informationen über das Auftreten und gegebenfalls die globale Gültigkeit von geomagnetischen Feldexkursionen zu gewinnen. Hierfür wurden etwa 75 Lavaflüsse des Transmexikanischen Vulkangürtels für paläomagnetische Studien beprobt. Eine Korrelation der mittleren Paläorichtungen von 56 mexikanischen Laven mit einer um Feldexkursionen ergänzten geomagnetischen Polaritätszeitskala, lieferte Hinweise auf 4 Exkursionen. Ein bedeutendes Ergebnis dieser Arbeit sind annährend komplett inversen Richtungen zweier Laven der Brunhes Chron. Dies gibt einen Hinweis darauf, dass diese Exkursionen kurze Zeitintervalle inverser Polarität mit globaler Gültigkeit repräsentieren könnten. Ein weiterer Schwerpunkt der vorliegenden Arbeit war, die neue MS Methode auf ihre Anwendbarkeit und Genauigkeit hin zu testen. Hierfür wurden Paläointensitätsexperimente an 11 historischen Laven aus Mexiko und Island durchgeführt. Ein Vergleich der Paläointensitäten mit Daten von magnetischen Observatorien ergab, dass die MS Methode einen generellen Trend zur Überschätzung der Paläointensität aufweisst, welcher anhand von komplementierenden gesteinsmagnetischen Daten mit magnetischen Mineralen im Mehrbereichsteilchen-Zustand in Verbindung gebracht werden konnte. Diese Beobachtung liefert demnach einen ersten Beweis dafür, dass die MS Methode möglicherweise nicht wie ursprünglich angenommen unabhängig vom Domänenzustand der Trägerminerale ist. Im weiteren wurde eine Komplementierung der Richtungsdaten mexikanischer Laven durch absolute Paläointensitätsbestimmungen angestrebt. Hierfür wurde die MS Methode herangezogen und zum ersten Mal in großem Umfang auf Vulkanite mit Altern von bis zu 3,5 Millionen Jahre angewendet. Ein Vergleich mit Rekonstruktionen des Dipol-Momentes, welche auf den Daten der gegenwärtigen globalen Paläointensitätsdatanbasis basieren, ergaben, dass diese MS Daten mit hoher statistischer Wahrscheinlichkeit im Mittel etwa 30% höher sind. Die generell zu hohen Paläonintensitäten nach der MS Methode bekräftigen daher die Ergebnisse von historischen Laven dieser Arbeit, sowie anderer experimenteller Studien an synthetischen Proben, bei denen Überschätzungen von MS Paläointensitäten von bis zu 30% festgestellt wurden. Der Process, aus dem diese Überschätzung der Paläointensität resultiert ist eine Asymetrie des Entmagnetisierungs- und Remagnetisierungsprozesses heisst, dass ein effektives Entmagnetisieren während der Remagnetisierung im angelegten Laborfeld erfolgt. Diese Asymetrie scheint besonders bei pseudo-Einbereichsteilchen ausgeprägt zu sein. Es wird allerdings davon ausgegangen, dass diese Überschätzung nicht größer ist, als was man bei einem Thellier Experiment an Proben mit ähnlicher magnetischer Korngröße erwarten würde. / The Earth’s magnetic field (EMF) is generated by convections in the electrically conducting liquid iron-rich outer core, modified by the Earth’s rotation. A drastic manifestation of the dynamics of this fluid body is the occurrence of geomagnetic field reversals in the Earth’s history but also geomagnetic excursions, which are more frequent features of otherwise stable polarity chrons, but often poorly constrained in the geological record. To better understand the origin of the field, we need to know how the field has varied on different geological timescales. This includes not only information about changes in the ancient field’s direction but also about the absolute intensity (palaeointensity) and the age. This palaeointensity record is needed for compiling a full-vector description of the field. A palaeomagnetic and palaeointensity study on lava flows allows gaining insights about the evolution of the EMF through time and space. However, constraining the EMF evolution over different geological timescales remains a difficult objective due to the paucity of available palaeointensity data. One new alternative approach in palaeointensity studies is the recently proposed multispecimen parallel differential pTRM (MS) method, which has potentially several advantages over the commonly used Thellier method, because it is in theory independent of magnetic domain state, less prone to biasing effects, such as thermal alteration and significantly faster to perform in the laboratory. A study of highly active volcanic regions, such as the Trans-Mexican Volcanic Belt, seems promising when attempting a full-vector reconstruction or when looking for field excursions. One aim of this thesis was to gain new information about the occurrence and global validity of geomagnetic excursions from the Brunhes- or Matuyama Chron. For this purpose some 75 lava flows from within the Trans-Mexican Volcanic Belt were sampled for palaeomagnetic analyses. The scatter of virtual geomagnetic poles from lavas younger than 1.7 Ma was used for estimating palaeosecular variation and was found to be consistent with latitude dependent Model G and other high quality palaeomagnetic data from Mexico. The palaeomagnetic mean-vectors of 56 lavas were correlated to the Geomagnetic Polarity Timescale supplemented with information on geomagnetic excursions. On the grounds of their associated radioisotopic ages, four lavas were tentatively correlated with known excursions from marine records. Two lava flows dating of Brunhes Chron were associated with the Big Lost and Delts/Stage 17 excursions, respectively. From further two flows dating of Matuyama Chron, one flow was associated with either the Santa Rosa- or Kamikatsura excursions, while the other could have been emplaced during the Gilsa excursion. The most significant outcome was the finding that both Brunhes excursional flows display nearly fully reversed directions that deviate almost 180°C from the expected normal polarity direction. This observation could indicate that in particular the Big Lost and Delta/Stage17 excursions may represent other short periods during which the field completed a full reversal for a short time, such as was previously found for other older cryptochrons or tiny wiggles. Another focus of this thesis was set on estimating the feasibility of the new MS method for routine palaeointensity determination. This was accomplished by applying the MS method to samples from 11 historical lava flows from Mexico and Iceland from which the actual field intensity was either known from contemporary observatory data, or deduced from magnetic field models. Comparing observed with expected intensity values allowed to test the accuracy of the MS method. It a was found that the majority of palaeointensity estimates after the MS method yielded results that were very close or indistinguishable within the range of uncertainty from the expected values. However, a general trend towards an overestimate in the palaeointensity was also observed, which, on the grounds of corroborating rock magnetic analyses, was associated with multidomain material. This observation was taken as first evidence that the MS method is not entirely independent of magnetic domain state, as was originally claimed. However, a second experiment in which a modification of the most widely used Thellier method was applied to sister samples from 5 Icelandic flows revealed that, in comparison to the MS method, the latter produced more accurate and statistically better defined palaeointensities. Thus, from these first results, the MS method appeared as a viable alternative for future palaeointensity studies. Subsequently it was attempted to corroborate the directional record from Mexican lavas with palaeointensity data. It was possible to acquire palaeointensity estimates for 32 out of 51 investigated lava flows. These new results revealed that the new MS palaeointensities for Mexico are, with a high degree of statistical significance, around 30% higher than expected. The generally high palaeointensities seem to corroborate the results obtained from historical lava flows in this study and other previous studies on synthetic samples where domain state effects were found to cause overestimates in the palaeointensity of up to 30 per cent in the MS method. The primary process that leads to this overestimate is assigned to an asymmetry in the demagnetisation and remagnetisation process. Yet, this overestimate is expected to be no larger than what might be expected from Thellier experiments performed on samples with a given degree of multidomain behaviour.

This thesis describes work on building numerical models of the Earth's magnetosphere using magnetohydrodynamics (MHD) and other related modeling methods. For many years, models that solve the MHD equations have been the main tool for improving our theoretical understanding of the large-scale dynamics of the Earth's magnetosphere. While the MHD models have been very successful in capturing many large-scale features, they fail to adequately represent the important drift physics in the inner magnetosphere. Consequently, the ring current, which contains most of the particle energy in the inner magnetosphere, is not realistically represented in MHD models. In this thesis, Chapter 2 and 3 will describe in detail our effort to couple the OpenGGCM (Open Geospace General Circulation Model), one of the major MHD models, to the Rice Convection Model (RCM), an inner magnetosphere ring current model, with the goal of including energy dependent drift physics into the MHD model. In Chapter 4, we will describe an initial attempt to use a direct-integration method to calculate Birkeland currents in the MHD code. Another focus of the thesis work, presented in Chapter 5, addresses a longstanding problem on how a geomagnetic substorm can occur within the closed field line region of the tail. We find a scenario of a bubble-blob pair formation in an OpenGGCM simulation just before the expansion phase of the substorm begins and the subsequent separation of the bubble and the blob decreases the normal component of the magnetic field until finally an X-line occurs. Thus the formation of the bubble-blob pair may play an important role in changing the magnetospheric configuration from a stretched field to the X-line formation that is believed to be the major signature of a substorm.

Les variations du champ magnétique terrestre sont documentées par les observatoires au sol et les satellites en orbite basse, pour des échelles de temps de l'année au siècle.Sur ces périodes, la dynamique du noyau externe -- là où est principalement généré le champ magnétique -- est fortement influencée par la rotation terrestre, qui tend à imposer une invariance dans la direction parallèle à l'axe de rotation.Dans cette thèse, j'étudie un modèle s'appuyant sur cette hypothèse de bidimensionnalité du champ de vitesse, le modèle quasi-géostrophique.Je présente une nouvelle dérivation de ce modèle par une approche variationnelle, plus adaptée aux fortes pentes des frontières du domaine sphérique.Je présente une étude modale des ondes hydro-magnétiques, qui pour la première fois prend en compte l'impact d'un champ magnétique imposé non-zonal.Deux groupes d'ondes magnéto-hydrodynamiques apparaissent alors : les ondes magnéto-Coriolis (centennales) et les ondes d'Alfvéen de torsion (interannuelle).Je décris l'évolution des ondes à mesure que l'on intensifie l'effet de la rotation, jusqu'à atteindre des paramètres géophysiques.Je discute également dans quel mesure une version du modèle quasi-géostrophique où la force de Lorentz est représentée par des produits quadratiques du champ magnétique est adapté pour l'interprétation de calculs numériques tridimensionnels de la dynamo. J'observe que pour les paramètres aujourd'hui accessibles à ces calculs, les forces magnétiques sont faibles. À long terme, nous espérons utiliser le modèle quasi-géostrophique dans le contexte de l'assimilation de données satellitaires. / Variations of the Earth's magnetic field are documented by ground observatories and low-orbiting satellites, for time scales from year to century.On such periods, dynamics of the outer core -- where the creation of the magnetic field takes place -- is strongly influenced by the Earth rotation, which tends to impose invariance of the flow in the direction parallel to the rotation axis.In this thesis report, I study a model based on this bi-dimensional velocity field hypothesis, the quasi-geostrophic model.I present a new mathematical formulation of this model through a variational approach, better suited to steep slopes on the boundaries of the spherical domain.I present a modal study of hydromagnetic waves, taking into account for the first time the impact of a non-zonal imposed magnetic field.Two groups of hydromagnetic waves are present : centennial magneto-Coriolis waves and interannual torsional Alfvén waves.I describe evolution of those waves as the effect of rotation is intensified until Earth-like parameters are reached.I also discuss in what measure an other version of the quasi-geostrophic model, where Lorentz force is represented by quadratic products of the magnetic field, can be adapted to understand tridimensional dynamo numerical simulations.I observe that for parameters available today, magnetic forces are weak.In the future, we hope to use the Quasi-geostrophic model in the context of satellite data assimilation.

abstract: The mineralogy of the deep mantle is one of the key factors for the chemical evolution of the Earth. The constituent minerals of the mantle rock control the physical properties of the mantle, which have significant impacts on the large-scale processes occurring in the Earth's interior. In my PhD research, I adopted experimental approaches to investigate the mineralogy and the physical properties of the Earth's materials in the deep mantle by using the diamond anvil cells (DACs) combined with in-situ X-ray diffraction techniques. First, I found that Ca-bearing bridgmanite can be stable in the deeper part of the Earth's lower mantle where temperature is sufficiently high. The dissolution of calcium into bridgmanite can change the physical properties of the mantle, such as compressibility and viscosity. This study suggests a new mineralogical model for the lower mantle, which is composed of the two layers depending on whether calcium dissolves in bridgmanite or forms CaSiO3 perovskite as a separate phase. Second, I investigated the mineralogy and density of the subducting materials in the Archean at the P-T conditions near 670 km-depth. The experiments suggest that the major phases of Archean volcanic crust is majoritic garnet and ringwoodite in the P-T conditions of the deep transition zone, which become bridgmanite with increasing pressure. The density model showed that Archean volcanic crust would have been denser than the surrounding mantle, promoting sinking into the lower mantle regardless of the style of the transportation in the Archean. Lastly, I further investigated the mineralogies and densities of the ancient volcanic crusts for the Archean and Proterozoic at the P-T conditions of the lower mantle. The experiments suggest that the mineralogy of the ancient volcanic crusts is composed mostly of bridgmanite, which is systemically denser than the surrounding lower mantle. This implies that the ancient volcanic crusts would have accumulated at the base of the mantle because of their large density and thickness. Therefore, the distinctive chemistry of the ancient volcanic crusts from the surrounding mantle would have given a rise to the chemical heterogeneities in the region for billions of years. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2020

The purpose of this action research project was to determine how my practice of using graphic organizers during instruction influenced my students' ability to summarize and comprehend significant fifth grade Earth Science content regarding the Earth's changing surface. A secondary purpose was to determine the students' perceptions of how concept mapping assisted in making connections to understand the fifth grade Earth Science content regarding the Earth's changing surface. The three processes used to collect data for this research were concept maps, focus groups and the pre- and post-test results. The themes that emerged were the ability to describe, categorize and classify details, the increased accuracy of the use of vocabulary and the memory of the concepts that students' ability to recall information and understand the Earth Science concepts as evidenced through summarization and comprehension through the pre- and post-test.

In this thesis, coda waves recorded by local seismographic networks will be analyzed to estimate the three-dimensional spatial distribution of scatterers (SDS). This will be done by using the single scattering approximation. This approach leads to a huge system of equations that can not be solved by traditional methods. For the first time, we will use the Simultaneous Iterative Reconstructive Technique (SIRT) to solve this kind of system in seismological applications. SIRT is slow but provides a means to carry out the inversion with greater accuracy. There is also a very fast non-iterative method that allows to carry out the inversion 102 times faster, with a higher resolution and reasonable accuracy: the Filtered Back-Projection (FBP). If one wishes to use this technique it is necessary to adapt it to the geometry of our problem. This will be done for the first time in this thesis. The theory necessary to carry out the adaptation will be developed and a simple expression will be derived to carry out the inversion.FBP and SIRT are then used to determine the SDS in southern India. Results are almost independent of the inversion method used and they are frequency dependent. They show a remarkably uniform distribution of the scattering strength in the crust around GBA. However, a shallow (0-24 km) strong scattering structure, which is only visible at low frequencies, seems to coincide with de Closepet granitic batholith which is the boundary between the eastern and western parts of the Dharwar craton.Also, the SDS is estimated for the Galeras volcano, Colombia. Results reveal a highly non-uniform SDS. Strong scatterers show frequency dependence, which is interpreted in terms if the scale of the heterogeneities producing scattering. Two zones of strong scattering are detected: the shallower one is located at a depth from 4 km to 8 km under the summit whereas the deeper one is imaged at a depth of ~37 km from the Earth's surface. Both zones may be correlated with the magmatic plumbing system beneath Galeras volcano. The second strong scattering zone may be probably related to the deeper magma reservoir that feeds the system.

viii Title: Dynamics of the bow shock and magnetopause Author: Karel Jelínek Department: Department of Surface and Plasma Science Supervisor: Prof. RNDr. Zdeněk Němeček, DrSc. Department of Surface and Plasma Science e-mail address: zdenek.nemecek@mff.cuni.cz Abstract: The interplanetary space is a unique laboratory which allows us to dis- cover (i) a behavior of the plasma under different conditions, (ii) origin of its insta- bilities, and (iii) its interaction with obstacles such as the Earth's magnetosphere. The present thesis analyzes the outer Earth's magnetosphere. The results are based on the in situ sensing by a variety of the spacecraft (e.g., IMP-8, INTERBALL-1, MAGION-4, Geotail, Cluster-II and Themis). The solar wind curently monitored by the WIND and ACE spacecraft near the La- grange point L1 affects by its dynamic pressure the Earth's magnetic field which acts as a counter-pressure and the boundary where these pressures are balanced is the magnetopause. Due to supersonic solar wind speed, the bow shock forms in front of the magnetopause and a region in between, where plasma flows around an obstacle is named the magnetosheath. The thesis contributes to a deaper understanding of the dependence of magnetopause and bow shock shapes and positions, especially, (1) on the orientation of the inter-...