Το Δεκέμβρη του 2013 στην Κέντρο Παιδείας Επιστημών της Πάτρας εγκαταστάθηκε και έλαβε μετρήσεις ένας σταθμός HELYCON τριών ανιχνευτών σπινθηρισμών και μία κεραία LOFAR. Σκοπός μας ήταν η καταγραφή Εκτεταμένων Ατμοσφαιρικών Καταιονισμών τόσο με το σταθμό HELYCON όσο και με την κεραία η οποία λειτούργησε με σήμα σκανδαλισμού από το σταθμό. Στην εργασία αυτή περιγράφεται η μέθοδος με την οποία βαθμονομήθηκε ο συγκεκριμένος σταθμός, η λειτουργία του καθώς και η ανάλυση των μετρήσεων. Αρχικά περιγράφεται η διαδικασία με την οποία βαθμονομούνται οι φωτοπολλάπλασιαστές στο εργαστήριο φυσικής του Ελληνικού Ανοικτού Πανεπιστημίου. Στην συνέχεια παρουσιάζονται τα στάδια από τα οποία περνάει ένας ανιχνευτής ώστε να εκτιμηθούν τα λειτουργικά του χαρακτηριστικά. Τέλος πραγματοποιούνται μετρήσεις βαθμονόμησης της ομάδας ανιχνευτών που θα αποτελέσουν ένα σταθμό HELYCON. Η εργασία ολοκληρώνεται με την ανάλυση των δεδομένων και τη σύγκρισή τους με τα αποτελέσματα που προέκυψαν από την προσομοίωση Monte Carlo. Η συμφωνία του πειράματος και της προσομοίωσης επιβεβαιώνουν την αξιόπιστη λειτουργία του σταθμού. Όλες οι παραπάνω διαδικασίες γίνονται σύμφωνα με την μεθοδολογία που παρουσιάζεται στη διδακτορική διατριβή του Δρ. Μπουρλή. / The subject of the current work is the extensive air showers, their Detection and reconstruction.

Hydraulic conductivity of variably-saturated soils is critical to understanding processes at the land surface. Yet measuring it over an area comparable to the resolution of land-surface models is fraught because of its strong spatial and temporal variations, which render point measurements nearly useless. We derived unsaturated hydraulic conductivity at the horizontal scale of hectometers and the vertical scale of decimeters by analyzing trends in soil moisture measured using the cosmic-ray neutron method. The resulting effective hydraulic conductivity remains close to its value at saturation over approximately half of the saturation range and then plummets. It agrees with the aggregate of 36 point measurements near saturation, but becomes progressively higher at lower water contents; the difference is potentially reconcilable by upscaling of point measurements. This study shows the feasibility of the cosmic-ray method, highlights the importance of measurement scale, and provides a route toward better understanding of land-surface processes.

My dissertation focuses on a relatively new field of study: the region immediately around galaxies known as the circumgalactic medium (CGM). The CGM holds vast quantities of mass and metals, yet its connection to galaxies is not well understood. My work uses cosmological hydrodynamic simulations and comparisons to data from Hubble's Cosmic Origins Spectrograph (COS) to understand the CGM's connection to galaxy evolution, gas accretion, outflows, star formation, and baryon cycling. This includes studies of the CGM's extent and physical conditions; the cause and nature of outflows; gas dynamics, including the first comprehensive study of tracers of inflowing and outflowing gas at low redshift (z=0.25); and direct comparison of theoretical results to observational data. Chapter 1 introduces my research and show its connection to galaxy evolution. Chapter 2 investigates hydrogen and metal line absorption around low-redshift galaxies in cosmological hydrodynamic simulations. This chapter studies different models for stellar outflows, physical conditions, and dependencies on halo mass. Chapter 3 examines the flow of gas into, out of, and around galaxies using a novel particle tracking technique. This chapter examines the baryon cycle in detail for our preferred model of stellar outflows. Chapter 4 compares our model results, including two separate prescriptions for outflows, with data from COS. We contrast these wind models, showing how they cycle baryons differently, and show degeneracies in observational diagnostics. In Chapter 5, I summarize and discuss plans for future research in this field, and how it can be more fully leveraged to understand galaxy evolution.

Nuclear particles hitting the silicon in a electronic device can cause a change in the data in a memory bit cell or in a flip-flop. The device is still working, but the data is corrupted and this is called a soft error. A soft error caused by a single nuclear particle is called a single event upset and is a growing problem. Research is ongoing at Saab aiming at how susceptible random access memories are to protons and neutrons. This thesis describes the development of equipment for measuring cosmic-ray effects on DRAM in laboratories. The system is built on existing hardware with a FPGA as the core unit. A short history of soft errors is also given and what causes it. How a DRAM works and basic operation is explained and the difference between a SRAM. The result is a working system ready to be used.

Several previous studies, including one using early Sanae radar data, have found examples of high speed ionospheric plasma flows on the nightside, mapping to the magnetospheric tail, during periods which were magnetically quiet. These high speed flows were interpreted to be associated with the release of energy from a rapid reconfiguration of tail magnetic field lines due to reconnection. Such events are now known as ‘TRINNIs’ or ‘tail reconnection during IMF northward, non-substorm intervals’. The purpose of this study was to identify further TRINNI events, using SuperDARN data from both hemispheres. In situations where the y-component of the Interplanetary Magnetic Field dominates over the z-component, the directions of both the high speed flows and the underlying convection pattern depend on the direction of the y-component. Some examples of likely TRINNI events for cases where the y-component was positive and negative are presented and discussed. The assumption of a non-substorm interval is justified by magnetometer and GOES satellite data, and the observations are discussed in relation to magnetic reconnection in the magnetotail. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

A three-dimensional (3D) steady-state electron modulation model based on Parker (1965) transport equation is applied to study the modelling of – 7 MeV galactic and Jovian electrons in the inner heliosphere. The latter is produced within Jupiter's magnetosphere which is situated at - 5 AU in the ecliptic plane. The heliospheric propagation of these particles is mainly described by the heliospheric diffusion tensor. Some elements of the tensor, such as the diffusion coefficient in the azimuthal direction, which were neglected in the previous two-dimensional modulation studies are investigated to account for the three-dimensional transport of Jovian electrons. Different anisotropic solar wind speed profiles that could represent solar minimum conditions were modelled and their effects were illustrated by computing the distribution of 7 MeV Jovian electrons in the equatorial regions. In particular, the electron intensity time-profile along the Ulysses spacecraft trajectory was calculated for these speed profiles and compared to the 3-10 MeV electron flux observed by the Kiel Electron Telescope (KET) on board the Ulysses spacecraft from launch (1990) up to end of its first out-of-ecliptic orbit (2000). It was found that the model solution computed with the solar wind profile previously assumed for typical solar minimum conditions produced good compatibility with observations up to 1998. After 1998 all model solutions deviated completely from the observations. In this study, as a further attempt to model KET observations more realistically, a new relation is established between the latitudinal dependence of the solar wind speed and the perpendicular polar diffusion. Based on this relation, a transition of an average solar wind speed from solar minimum conditions to intermediate solar activity and to solar maximum conditions was modelled based on the assumption of the time-evolution of large polar coronal holes and were correlated to different scenarios of the enhancement of perpendicular polar diffusion. Effects of these scenarios were illustrated, as a series of steady-state solutions, on the computed 7 MeV Jovian and galactic electrons in comparison with the 3-10 MeV electron observed by the KET instrument from the period 1998 up to the end of 2003. Subsequent effects of these scenarios were also shown on electron modulation in general. It was found that this approach improved modelling of the post-1998 discrepancy between the model and KET observations but it also suggested the need for a time-dependent 3D electron modulation model to describe modulation during moderate to extreme solar maximum conditions. / Thesis (M.Sc.)--North-West University, Potchefstroom Campus, 2004.

The interest in the role of the solar wind termination shock (TS) and heliosheath in cosmic ray (CR) modulation studies has increased sigm6cantly as the Voyager 1 and 2 spacecraft approach the estimated position of the TS. For this work the modulation of galactic CR protons, anti-protons, electrons with a Jovian source, positrons, Helium, and anomalous protons and Helium, and the consequent charge-sign dependence, are studied with an improved and extended two-dimensional numerical CR modulation model including a TS with diffusive shock acceleration, a heliosheath and drifts. The modulation is computed using improved local interstellar spectra (LIS) for almost all the species of interest to this study and new fundamentally derived diffusion coefficients, applicable to a number of CR species during both magnetic polarity cycles of the Sun. The model also allows comparisons of modulation with and without a TS and between solar minimum and moderate maximum conditions. The modulation of protons and Helium with their respective anomalous components are also studied to establish the consequent charge-sign dependence at low energies and the influence on the computed p/p, e-/p, and e-/He. The level of modulation in the simulated heliosheath, and the importance of this modulation 'barrier' and the TS for the different species are illustrated. From the computations it is possible to estimate the ratio of modulation occurring in the heliosheath to the total modulation between the heliopause and Earth for the mentioned species. It has been found that the modulation in the heliosheath depends on the particle species, is strongly dependent on the energy of the CRs, on the polarity cycle and is enhanced by the inclusion of the TS. The computed modulation for the considered species is surprisingly different and the heliosheath is important for CR modulation, although 'barrier' modulation is more prominent for protons, anti-protons and Helium, while the heliosheath cannot really be considered a modulation 'barrier' for electrons and positrons above energies of ~150 MeV. The effects of the TS on modulation are more pronounced for polarity cycles when particles are drifting primarily in the equatorial regions of the heliosphere along the heliospheric current sheet to the Sun, e.g. the A < 0 polarity cycle for protons, positrons, and Helium, and the A > 0 polarity cycle for electrons and anti-protons. This study also shows that the proton and Helium LIS may not be known at energies <~ 200 MeV until a spacecraft actually approaches the heliopause because of the strong modulation that occurs in the heliosheath, the effect of the TS, and the presence of anomalous protons and Helium. For anti-protons, in contrast, these effects are less pronounced. For positrons, with a completely different shape LIS, the modulated spectra have very mild energy dependencies <~ 300 MeV, even at Earth, in contrast to the other species. These characteristic spectral features may be helpful to distinguish between electron and positron spectra when they are measured near and at Earth. These simulations can be of use for future missions to the outer heliosphere and beyond. / Thesis (Ph.D. (Physics))--North-West University, Potchefstroom Campus, 2004.

The thesis proposes an indirect indicator of the geomagnetic field variations, i.e. the hard cosmic ray flux. Analysing HCRF variations, a prognostic scheme of a leap of cardiovascular diseases was drafted. The application of this method, most probably, will inform people about the geomagnetic impact and will supplement other existing methods employed to reduce a leap of cardiovascular diseases.

No description available.

This cumulative dissertation explored the use of the detection of natural background of fast neutrons, the so-called cosmic-ray neutron sensing (CRS) approach to measure field-scale soil moisture in cropped fields. Primary cosmic rays penetrate the top atmosphere and interact with atmospheric particles. Such interaction results on a cascade of high-energy neutrons, which continue traveling through the atmospheric column. Finally, neutrons penetrate the soil surface and a second cascade is produced with the so-called secondary cosmic-ray neutrons (fast neutrons). Partly, fast neutrons are absorbed by hydrogen (soil moisture). Remaining neutrons scatter back to the atmosphere, where its flux is inversely correlated to the soil moisture content, therefore allowing a non-invasive indirect measurement of soil moisture. The CRS methodology is mainly evaluated based on a field study carried out on a farmland in Potsdam (Brandenburg, Germany) along three crop seasons with corn, sunflower and winter rye; a bare soil period; and two winter periods. Also, field monitoring was carried out in the Schaefertal catchment (Harz, Germany) for long-term testing of CRS against ancillary data. In the first experimental site, the CRS method was calibrated and validated using different approaches of soil moisture measurements. In a period with corn, soil moisture measurement at the local scale was performed at near-surface only, and in subsequent periods (sunflower and winter rye) sensors were placed in three depths (5 cm, 20 cm and 40 cm). The direct transfer of CRS calibration parameters between two vegetation periods led to a large overestimation of soil moisture by the CRS. Part of this soil moisture overestimation was attributed to an underestimation of the CRS observation depth during the corn period ( 5-10 cm), which was later recalculated to values between 20-40 cm in other crop periods (sunflower and winter rye). According to results from these monitoring periods with different crops, vegetation played an important role on the CRS measurements. Water contained also in crop biomass, above and below ground, produces important neutron moderation. This effect was accounted for by a simple model for neutron corrections due to vegetation. It followed crop development and reduced overall CRS soil moisture error for periods of sunflower and winter rye. In Potsdam farmland also inversely-estimated soil hydraulic parameters were determined at the field scale, using CRS soil moisture from the sunflower period. A modelling framework coupling HYDRUS-1D and PEST was applied. Subsequently, field-scale soil hydraulic properties were compared against local scale soil properties (modelling and measurements). Successful results were obtained here, despite large difference in support volume. Simple modelling framework emphasizes future research directions with CRS soil moisture to parameterize field scale models. In Schaefertal catchment, CRS measurements were verified using precipitation and evapotranspiration data. At the monthly resolution, CRS soil water storage was well correlated to these two weather variables. Also clearly, water balance could not be closed due to missing information from other compartments such as groundwater, catchment discharge, etc. In the catchment, the snow influence to natural neutrons was also evaluated. As also observed in Potsdam farmland, CRS signal was strongly influenced by snow fall and snow accumulation. A simple strategy to measure snow was presented for Schaefertal case. Concluding remarks of this dissertation showed that (a) the cosmic-ray neutron sensing (CRS) has a strong potential to provide feasible measurement of mean soil moisture at the field scale in cropped fields; (b) CRS soil moisture is strongly influenced by other environmental water pools such as vegetation and snow, therefore these should be considered in analysis; (c) CRS water storage can be used for soil hydrology modelling for determination of soil hydraulic parameters; and (d) CRS approach has strong potential for long term monitoring of soil moisture and for addressing studies of water balance. / In dieser kumulativen Dissertation wird die Detektion des natürlichen Hintergrunds von schnellen Neutronen, das sogenannte “Cosmic-Ray Neutron Sensing” (CRS), zur Messung von Bodenfeuchte auf der Feldskala in landwirtschaftlich genutzten Flächen untersucht. Die kosmische Primärstrahlung durchdringt die oberste Atmosphäre, und interagiert mit atmosphärischen Teilchen. Durch diese Wechselwirkungen entstehen Kaskaden hochenergetischer Teilchen die bis in die Erdoberfläche eindringen, wobei schnelle Neutronen entstehen. Teilweise werden diese durch Wasserstoff (Bodenfeuchte) absorbiert, teilweise zurück in die Atmosphäre gestreut. Dieser Neutronenfluss über dem Boden korreliert invers mit der Bodenfeuchte, was so eine non-invasive und indirekte Bodenfeuchteschätzung ermöglicht. Die CRS-Methode wird vor allem in einer Feldstudie auf einem Ackerland in Potsdam (Brandenburg, Deutschland), einschließlich dreier Phasen mit Anbau von Mais, Sonnenblume und Winterroggen getestet und beurteilt. Darüber hinaus wurde ein Feldmonitoring im Schäfertaleinzugsgebiet (Harz, Deutschland) durchgeführt, um das Potential von Langzeit-CRS-Messungen gegenüber herkömmlich erhobenen bodenhydraulischen Daten abzuschätzen. Im ersten Untersuchungsgebiet wurde die CRS-Methode kalibriert und mittels verschiedener Bodenfeuchtemessansätze validiert. In der Maisanbauphase wurden die Bodenfeuchte-Punktmessungen zunächst nur an der nahen Bodenoberfläche durchgeführt. In den folgendenen Anbauphasen (Sonnenblume und Winterroggen) wurden dann die Sensoren in drei unterschiedlichen Tiefen (5 cm, 20 cm und 40 cm) installiert. Die direkte Übertragung der CRS-Kalibrierparameter zwischen zwei Vegetationsperioden führte zu einer starken Überschätzung der CRS-Bodenfeuchte. Ein Teil der überschätzten Bodenfeuchte wurde der Unterschätzung der CRS-Beobachtungstiefe während der Maisperiode (5-10 cm) zugeschrieben, welche später basierend auf Werten zwischen 20-40 cm in anderen Anbauperioden (Sonnenblume und Winterroggen) neuberechnet wurde. Gemäß der Ergebnisse dieser Beobachtungsperioden mit verschiedenen Feldfrüchten, spielte die Vegetation eine wichtige Rolle für die CRS-Messungen, da das Wasser, das in der über- und unterirdischen Biomasse vorhanden ist, die Neutronen bedeutend abdämpft. Dieser Effekt, sowie der Einfluss des Getreidewachstums und des reduzierten Gesamt-CRS-Bodenfeuchte-Fehlers, wurden in ein einfaches Model zur vegetationsbedingten Neutronenkorrektur berücksichtigt. So wurde ein gekoppelter HYDRUS-1D- und PEST-Ansatz angewendet, um bodenhydraulische Parameter auf dem Feldmassstab während der Sonnenblumen-Phase invers abzuschätzen. Dann wurden die inversen Schätzungen der effektiven bodenhydraulischen Eigenschaften innerhalb des von CRS beobachteten Volumens durch die lokalen Bodeneigenschaften (Modellierung und Messungen) validiert. Abgesehen von Unterschieden auf Grund der Beobachtungstiefe und somit des Volumens, wurden hierbei erfolgreiche Ergebnisse erzielt. Dieser einfache Ansatz unterstreicht das zukünftige Forschungspotential, z.B. um mit Hilfe von Bodenfeuchten aus CRS-Messungen Modelle auf der Feldskala zu parametrisieren. Im Schäfertaleinzugsgebiet wurden die Langzeit-CRS-Messungen mit Nie-derschlags- und Evapotranspirations-Raten abgeglichen. Bei einer monatlichen Auflösung korrelierte die Änderung des CRS-Bodenwasserspeichers mit diesen beiden Wettervariablen. Die Wasserbilanz konnte jedoch auf Grund fehlender Informationen bezüglich Grundwasser, Abfluss des Einzugesgebiets, etc. nicht geschlossen werden. Darüber hinaus wurde, wie auch am Potsdamer Standort, festgestellt, dass das CRS-Signal stark von Schneefall und Schneeakkumulationen beeinflusst wird. Eine einfache Anwendung zur Schneemessung mittels CRS wurde für den Schäfertalfall vorgestellt. Abschließend zeigte sich, dass (a) „Cosmic-Ray Neutron Sensing“ (CRS) ein großes Potential hat, Messungen der mittleren Bodenfeuchte auf der Feldskala im Bereich landwirtschaftlich genutzter Flächen zu realisieren; (b) die CRS-Bodenfeuchte stark durch andere Wasserspeicher, wie Vegetation und Schnee beeinflusst wird, und dies im Rahmen von Analysen berücksichtigt werden sollte; (c) die CRS-Messungen über eine bodenhydraulische Modellierung zur Bestimmung von bodenhydraulischen Paramtern genutzt werden kann; und (d) der CRS-Ansatz ein großes Potential für Langzeit-Bodenfeuchte-Monitoring und für Wasserbilanzstudien hat.