Doctor of Philosophy

dissertationEvidence of a number of interrelated energy dependent intermediate-scale anisotropies have been found in the arrival directions of proton-like ultra-high energy cosmic rays (UHECR) using 7 years of Telescope Array (TA) data. These are found using analysis techniques that have been developed for this dissertation. Using surface detector (SD) data the reported TA "Hotspot" excess, E 1019.75 eV, is found to correspond to a deficit, or "Coldspot," of events for 1019.1 E<1019.75 eV at 142 R.A., 40 Dec. The global posttrial significance of this Hot/Coldspot event density asymmetry is found to be 5.1s (p = 1.56 10 7). This Hot/Coldspot feature is the combination, at the same location, of an energy spectrum anisotropy with a 3.74s significance for energies E 1019.2 eV and an energy-distance correlation with a 3.34s significance for energies E 1019.3 eV. The UHECR Hotspot alone is analyzed using a new kernel density estimation (KDE) anisotropy method and found to have a 3.65s significance (E 1019.75 eV). These features suggest energy dependent magnetic deflection of UHECR. The composition of UHECR primary particles is also studied using a new "Quality Factor Analysis" pattern recognition event selection for fluorescence detectors (FD). This minimizes the energy dependence of the resolution of extensive air shower (EAS) Xmax depth. Also, a new statistical method making use of all higher moments than the mean hXmaxi shower depth distribution is developed - as there is large disagreement in hXmaxi between all EAS simulation models. There is also an uncertainty, just as large, for any particular model, given uncertainties in particle interaction parameters extrapolated to much higher energies from Large Hadron Collider (LHC) data. The TA hybrid FD/SD data is found to be statistically compatible with a pure proton composition, though not incompatible with a light mixed composition, for all models of EAS above E 1018.4 eV. There is also no statistically significant evidence of the composition getting heavier at the highest energies. The combined information of a proton-like light composition, and anisotropy evidence suggestive of energy dependent magnetic deflection of UHECR, should be useful for informing future source searches and models of intergalactic propagation through magnetic fields

Spine-sheath jet model for low-luminosity AGNs

In several jetted AGNs, structured jets have been observed. In particular spine-sheath configurations where the jet is radially divided into two or more zones of different flow velocities. We present a model based on the particle and radiation transport code CR-ENTREES. Here, interaction rates and secondary particle and photon yields are pre-calculated by Monte Carlo event generators or semi-analytical approximations. These are then used to create transition matrices, that describe how each particle spectrum evolves with time. This code allows for arbitrary injection of primary particles, and the possibility to choose which interaction to include (photo-meson production, Bethe-Heitler pair-production, inverse-Compton scattering, $\gamma$-$\gamma$ pair production, decay of all unstable particles, synchrotron radiation -- from electrons, protons, and all relevant secondaries before their respective decays -- and particle escape). In addition to the particle and radiation interactions taking place in each homogeneous zone, we implement the feedback between the two zones having different bulk velocities. The main mechanism at play when particles cross the boundary between the two zones is shear acceleration. We follow a microscopic description of this acceleration process to create a corresponding transition matrix and include it in our numerical setup. Furthermore, each zone's radiation field can be used as an external target photon field for the other zone's particle interactions. We present here the first results of the effect of a two-zone spine-sheath jet, by applying this model to typical low-luminosity AGNs.Comment: PoS 444 (38th ICRC) 958 (accepted

Hydrological Partitioning in the Critical Zone: Recent Advances and Opportunities for Developing Transferable Understanding of Water Cycle Dynamics

Hydrology is an integrative discipline linking the broad array of water-related research with physical, ecological, and social sciences. The increasing breadth of hydrological research, often where subdisciplines of hydrology partner with related sciences, reflects the central importance of water to environmental science, while highlighting the fractured nature of the discipline itself. This lack of coordination among hydrologic subdisciplines has hindered the development of hydrologic theory and integrated models capable of predicting hydrologic partitioning across time and space. The recent development of the concept of the critical zone (CZ), an open system extending from the top of the canopy to the base of groundwater, brings together multiple hydrological subdisciplines with related physical and ecological sciences. Observations obtained by CZ researchers provide a diverse range of complementary process and structural data to evaluate both conceptual and numerical models. Consequently, a cross-site focus on ‘‘critical zone hydrology’’ has potential to advance the discipline of hydrology and to facilitate the transition of CZ observatories into a research network with immediate societal relevance. Here we review recent work in catchment hydrology and hydrochemistry, hydrogeology, and ecohydrology that highlights a common knowledge gap in how precipitation is partitioned in the critical zone: ‘‘how is the amount, routing, and residence time of water in the subsurface related to the biogeophysical structure of the CZ?’’ Addressing this question will require coordination among hydrologic subdisciplines and interfacing sciences, and catalyze rapid progress in understanding current CZ structure and predicting how climate and land cover changes will affect hydrologic partitioning

Combined fit to the spectrum and composition data measured by the Pierre Auger Observatory including magnetic horizon effects

The measurements by the Pierre Auger Observatory of the energy spectrum and mass composition of cosmic rays can be interpreted assuming the presence of two extragalactic source populations, one dominating the flux at energies above a few EeV and the other below. To fit the data ignoring magnetic field effects, the high-energy population needs to accelerate a mixture of nuclei with very hard spectra, at odds with the approximate E$^{-2}$ shape expected from diffusive shock acceleration. The presence of turbulent extragalactic magnetic fields in the region between the closest sources and the Earth can significantly modify the observed CR spectrum with respect to that emitted by the sources, reducing the flux of low-rigidity particles that reach the Earth. We here take into account this magnetic horizon effect in the combined fit of the spectrum and shower depth distributions, exploring the possibility that a spectrum for the high-energy population sources with a shape closer to E$^{-2}$ be able to explain the observations