Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 155-158).

Abstract Cosmic rays are energetic particles traversing space that bombard Earth's atmosphere frequently and produce vast particle showers while interacting with air nuclei. The origin and composition of high-energy cosmic rays in the knee region (1015 - 1016 eV) of the cosmic-ray energy spectrum remain unclear despite of novel detection and analysis methods used in various surface and underground experiments. The understanding of the knee has improved from its first detection but still there is notable deviation in results between experiments depending on the used detection methods. The aim of the underground cosmic-ray experiment EMMA (Experiment with Multi-Muon Array) is to shed more light on the origin of the knee. EMMA is based on the idea to measure the lateral shape of high-energy muon component produced in cosmic-ray initiated particle showers on an event-by-event basis, that is, separately for each shower, offering a unique way to study the composition of cosmic rays in the knee region. The present work comprises the design, development and implementation of a comprehensive set of analysis tools for the EMMA experiment. It includes the development of the simulation program to generate realistic event data, the track reconstruction program ETANA to reconstruct hits and tracks in detector stations, the visualisation program EmmaEve to scan events, the graphical monitoring program EmmaDiagnosticsGUI to control the functionality of detectors on-line, the efficiency monitoring program to control chamber efficiencies in three-layer stations and the design of the EMMA database to store reconstruction results. Especially the design and tests of ETANA form the backbone of the present work as its optimised performance is crucial for the analysis of EMMA data. Furthermore, in the present work the influence of rock overburden above EMMA on the properties of high-energy muons is investigated by detailed simulations. The reconstruction of hits in drift chambers is studied with measured data including the estimation of the quality of reconstructed hits, the functionality of hit formation procedure and the influence of afterpulses on hit reconstruction. The validity of simulated data that are generated by the EMMA event generation program is evaluated by comparing simulated and measured data with each other. Finally, synergy benefits between the EMMA and ALICE experiments are discussed, which are both underground experiments but different in nature.

Modeling the highly energetic particles known as galactic cosmic rays is a highly nontrivial task. This process may require numerical simulations of the complex processes occurring continuously in the heliosphere due to changes in solar wind reflecting the solar activity. However, if reasonable assumptions are employed, considering only the diffusion and convection processes, the above phenomenon can be reduced to a simplified scenario that can be modeled analytically. The variable solar wind may be responsible for solar modulation of galactic cosmic rays. The aforementioned, in addition to the postulated role of cosmic rays in climate change, has led to the following questions: what is the relationship between galactic cosmic rays and solar wind? What are the possible effects of solar wind on galactic cosmic ray flux? In an attempt to address these questions, we have modeled the transport of galactic cosmic rays in the heliosphere theoretically. Our model describes solar modulation and transport of galactic cosmic rays in the heliosphere mainly in terms of the size of the heliosphere, timedependent solar wind, and a uniform diffusion coefficient. Our results suggest that solar wind causes significant decrease in galactic cosmic ray flux at r ≈ 1AU. In further investigation, we examine a short-time variation of the calculated flux, and the result is reflected by exposing a negative correlation of −0.988 ± 0.001 between galactic cosmic ray flux variation and the solar wind variation at r ≈ 1AU. This outcome may suggest that the higher the solar wind, the lower the galactic cosmic ray flux and vice-versa. For completeness, we compared our results with available observational data that shows a good fit to the model. Thus, based on our model results, it may be possible to predict that galactic cosmic ray flux variation and solar wind variation at Earth are negatively correlated.

The purpose of this study is to determine the characteristics of the solar cosmic ray flux. This report describes the design and construction of a cosmic ray detector system used in this study and describes the analysis of the data obtained from these systems.

This thesis contains a brief description of the apparatus, the procedure, and the results of an investigation of the absorption of cosmic rays in thin absorbers. The existence of an anomalous maximum at a thickness of 10.5 cm. of lead is reported, which is tenatively interpreted as being caused by the production of a penetrating ionizing radiation by a neutral radiation through some seemingly unknown process. / Thesis / Master of Science (MS)

A surface search was made using a small-area four-layer scintillator detector. Slow lightly ionizing particles created in cosmic ray interactions in the atmosphere which arrived within 13 ms of the shower front were searched for. In a live time of 2.55 x 10⁵ s 394,608 showers of two or more muons and 21,038 showers of four or more muons were recorded. No multiple muon events were recorded in which a trailing particle was identified above the expected random background, with a velocity between 7.4 x 10⁻⁵c and 6.7 x 10⁻³c. The detector operated without a trigger and used interplanar timing information to identify potential events, and operated above a threshold of 1/400 of that of a minimum ionizing muon. / Ph. D.

Abstract The thesis is focused on the reconstruction of long-term cosmic ray variability using proxy data. The 11-year solar cycle in production/deposition rates of cosmogenic nuclides ¹⁰Be and ¹⁴C has been modelled for the conditions of grand minima and maxima of solar activity (namely, Maunder Minimum and Grand Modern Maximum). The result shows that contrary to the observed strongly suppressed amplitude of the solar cycle in sunspots during Maunder Minimum relatively to Grand Modern Maximum, the cosmic ray proxies have the comparable amplitudes during the two periods. This phenomenon is caused by the nonlinear relation between solar activity and production of cosmogenic nuclides. In addition to well-established proxies of cosmic rays, nitrate in polar ice has been recently proposed as a new proxy for the long-term variability of galactic cosmic rays. The thesis contains two tests of its applicability for this purpose with TALDICE and EPICA-Dome C ice core data from Central Antarctica. The results support the proposal for the multimillennial time scales. Lunar samples acquired during the Apollo missions are important data for estimating the averaged energy spectra of galactic cosmic rays and solar energetic particles at the Earth’s orbit. The development in modelling of the interaction between energetic particles and matter makes it necessary to revise the earlier results. Because of that, new production rates of ¹⁰Be and ¹⁴C in lunar samples by galactic cosmic rays and solar energetic particles have been computed. New accurate cosmic ray reconstructions from natural archives containing cosmogenic nuclides use sophisticated climatic models requiring yield functions of the nuclides with high altitude resolution. These functions have been computed for ⁷Be, ¹⁰Be, ¹⁴C, ²²Na, and ³⁶Cl in the Earth’s atmosphere. Overall, the major purpose of the studies presented in the thesis is to increase the quality of reconstructions of the long-term cosmic ray variability for better understanding of the solar and heliospheric physics. / Original papers The original publications are not included in the electronic version of the dissertation. Poluianov, S. V., Usoskin, I. G., & Kovaltsov, G. A. (2014). Cosmogenic Isotope Variability During the Maunder Minimum: Normal 11-year Cycles Are Expected. Solar Physics, 289(12), 4701–4709. https://doi.org/10.1007/s11207-014-0587-6 Poluianov, S., Traversi, R., & Usoskin, I. (2014). Cosmogenic production and climate contributions to nitrate record in the TALDICE Antarctic ice core. Journal of Atmospheric and Solar-Terrestrial Physics, 121, 50–58. https://doi.org/10.1016/j.jastp.2014.09.011 Poluianov, S., Artamonov, A., Kovaltsov, G., & Usoskin, I. (2015). Energetic particles in lunar rocks: Production of cosmogenic isotopes. Proceedings of Science, 30-July-2015, art. no. 051 . Traversi, R., Becagli, S., Poluianov, S., Severi, M., Solanki, S. K., Usoskin, I. G., & Udisti, R. (2016). The Laschamp geomagnetic excursion featured in nitrate record from EPICA-Dome C ice core. Scientific Reports, 6(1). https://doi.org/10.1038/srep20235 Poluianov, S. V., Kovaltsov, G. A., Mishev, A. L., & Usoskin, I. G. (2016). Production of cosmogenic isotopes 7Be, 10Be, 14C, 22Na, and 36Cl in the atmosphere: Altitudinal profiles of yield functions. Journal of Geophysical Research: Atmospheres, 121(13), 8125–8136. https://doi.org/10.1002/2016jd025034

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High-energy neutrinos are capable of carrying information over vast distances, and neutrino telescopes such as AMANDA-II provide the means to probe deep inside the violent and energetic interior of the universe. AMANDA-II is located in the glacial ice at South Pole in Antarctica and is optimised to detect Cherenkov emission from neutrino-induced muon tracks with energies above 100 GeV. Data acquired in 2003 with the AMANDA-II detector were searched for a non-localised flux of neutrinos with energies in excess of 1 PeV. Because of the energy dependence of the neutrino mean free path, the Earth is essentially opaque to neutrinos above PeV energies. Combined with the limited overburden of the AMANDA-II detector (about 1.5 km), this means that a potential ultra-high energy neutrino signal will be concentrated at the horizon. The background for the analysis consists of large bundles of muons produced in atmospheric air showers. Owing to their energy losses, muons cannot penetrate the Earth, and the background will be downwards moving. After applying different selection criteria, one event was observed in the final data sample, while 0.16±0.04 background events are expected. The corresponding 90% confidence level upper limit is 4.3. The expected number of neutrino signal events for a 10-6 E-2 GeV/(s sr cm2 ) flux assuming a Φ(νe) : Φ(νμ) : Φ(ντ) = 1:1:1 flavour ratio is 4.1±0.2, yielding an upper limit on the all-flavour neutrino flux of E2 Φ90 ≤ 1.1∙10-6 GeV/(s sr cm2 ), including systematics and with the central 90% of the signal found in the energy range 480 TeV - 1.6 EeV.

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