The tidal torque theory for the origin of galactic rotation has been investigated using N-body computer simulations. The results show that this process is considerably less efficient than was previously thought, though consistent with recent observations of the rotation of giant elliptical galaxies. Spectroscopic observations of three elliptical galaxies along both major and minor axes are presented. Two galaxies were found to be slowly rotating, inconsistent with rotationally supported oblate spheroids. No convincing evidence for minor axis rotation was found. An investigation of the clustering of particles in Friedmann models of the Universe has been carried out using N-body simulations. The results of these computations have been analysed in terms of the two- and three- point correlation functions and various velocity statistics. It is found that the shapes of the two- and three-point functions are dependent upon the cosmological density parameter Ω, and that the shape of the two-point function is in rough agreement with simple analytic treatments based on the homogeneous spherical cluster model for the collapse of protoclusters. The effects of particle discreteness and two-body relaxation, which are particularly important in the N-body models are examined. The approach is compared to the detailed kinetic theory calculations of Davis and Peebles. The cosmological implications of the results are discussed. Other statistics, such as the multiplicity function are also considered.

This thesis describes studies of nuclear active particles (NAPs) in the cosmic radiation over the momentum range 1-30 GeV/c. Both unaccompanied particles and NAPs in extensive air showers (EAS) are studied near sea level at Durham using an air-gap magnet spectrograph in conjunction with a neutron monitor. Details are given of the design of the spectrograph, neutron monitor and associated equipment as used for measurements on unaccompanied NAPs (Chapter 2), and the techniques used for derivation of the momentum spectra from the basic data are described in Chapter 3. The results, in the form of momentum spectra of unaccompanied protons and negative pions, and the limited analysis of NAPs in EAS are presented in Chapter 4 where they are compared with the results of other workers. Measurements of the momentum of NAPs in EAS were found to be difficult and the data are mainly concerned with the response of the neutron monitor to EAS. A model of the propagation of cosmic rays through the atmosphere, which was mainly intended for predictions of the properties of large EAS, is described and used to predict the momentum spectra of unaccompanied particles at sea level. The results of this prediction are compared with the experimental data (Chapter 5) and the results of other model predictions (Chapter 6). It is shown that no single model, when combined with a reasonable spectrum of primary cosmic rays, can adequately explain all the data on unaccompanied particles at sea level. It is also shown that the spectra of high energy protons and pions are likely to be the sea level measurements which are most sensitive to the form of the primary cosmic ray spectrum.

This thesis is concerned with the production of evaporation neutrons in neutron monitors by the charged particle components of the cosmic radiation at sea level and their detection. The evaporation neutron detection efficiency of a modified I6Y - type monitor is measured using a novel technique which uses stopping negative muons as a source of neutrons, and the result is compared with that expected from previous measurements of other monitors. Use is made of this result in an experimental study of neutron production by unaccompanied cosmic ray protons, pions and muons in the momentum range 1-30 GeV/c. The experiment has, employed an air-gap magnet spectrograph in conjunction with the monitor, and the results of this study are compared with previous work. They confirm previous findings that the yield of evaporation neutrons in monitors from protons and pions is significantly overestimated by the only available theoretical model, and suggestions, are made to account for this discrepancy. Within fairly large statistical errors, the measured neutron production by fast muons agrees with the theoretical predictions. An examination is made of the possibility of using a neutron monitor in conjunction with an air shower detection array to measure the changes in slope of the nuclear active particle (NAP) energy spectrum in extensive air showers (HAS) of energy l0(^17)eV at sea level which may arise due to primary particles of different atomic mass number and fluctuations in the longitudinal development of proton induced showers. Using NAP spectra predicted by a mathematical model of the EAS development it is found that monitors of conventional design are unlikely to be sensitive to these changes although the total neutron yield per shower could be used as a measure of the expected differences in the NAP flux.

One of the most prominent and well established features in the primary energy spectrum of cosmic rays observed at the Earth is the change of slope occurring at several 10(^15) eV. A comprehensive survey of experimental EAS data is used to establish the integral size spectrum for electrons and muons at sea level and for electrons at mountain altitudes. A model for the diffusion of protons in the Galaxy is developed based on experimental observations of the structure of hydrogen in the interstellar medium and of the magnetic field strengths and their orientations in galactic space. A numerical treatment of the diffusion problem is adopted. A pre-diction is made of the primary cosmic ray proton energy spectrum at the top of the atmosphere. A survey of the data on cosmic ray primaries with energies below ~10(^11) eV obtained by balloon and satellite experiments, was used to establish the relative abundances of all cosmic rays. By assuming that the cosmic ray composition remains the same at EAS energies the primary spectrum representing diffusion of cosmic rays with mixed composition is derived. Comparison of the theory with experiment was made by converting the integral primary energy spectrum representing diffusion to the integral size spectrum by using results of EAS simulations through the atmosphere. Excellent agreement of theory with experiment is obtained provided that the primary cosmic radiation is protonic. The problems encountered with ensuring isotropy of cosmic rays at the Earth are dealt with in great detail and are shown to create little problem over the part of the spectrum considered provided the solar system lies in the centre of the spiral arm. Finally, a model is proposed as an alternative to that of diffusion which provides a qualitative but adequate explanation for the origin of the 'knee'.

An experiment to observe to atmospheric Cerenkov light produced in extensive air showers, has been under development at the British Universities' joint air shower array at Haverah Park, since 1972. This thesis is concerned with the Cerenkov light measurments made at Haverah Park during the U.K. winter of 1975/76, when the experimental equipment was first improved to its present specification. An introduction to extensive air showers and the relevance of Cerenkov light studies, is followed by an account of the theoretical aspects of Cerenkov radiation. The most recent computer simulations of the features of Cerenkov light in extensive air showers are briefly described. A detailed account of the design and performance of the current Cerenkov light detection equipment is given, and the measurements made are reported. Very detailed measurements of the Cerenkov light in air showers can be made with the equipment. The average characteristics of the Cerenkov light in showers of energies around 5 x 10(^17) eV are established. Measurements of both the photon density and the details of the light pulse shape are made at core distances up to about 600 m. The curvature of the Cerenkov light front in air showers is also determined, from measurements of the arrival times of the light. A Cerenkov light measure of primary particle energy is identified. The dependences of the Cerenkov light parameters on shower energy and zenith angle are quantified, and are used to estimate the sensitivities of the parameters to depth of shower cascade maximum. The data measured here agree well with earlier measurements, where such comparison may be made. The measured average characteristics of the Cerenkov light in air showers are found to be in good agreement with predictions from the recent computer simulations. Comparison of the experimental and theoretical data, leads to an estimate of the average atmospheric depth at which showers reach cascade maxima. It is not possible, however, to interpret this estimate in terms of primary particle mass. Finally, the fluctuations in Cerenkov light signals are examined, by studying the light measurements made in a small sample of individual showers. It is shown that fluctuation values of Cerenkov light parameters, contain information about shower development, which is additional to that derived from the average characteristics of the light parameters. An upper limit for the range of atmospheric depths over which showers reach cascade development maxima, as a result of variations in the nucleon interactions in their cascades, is derived. It is concluded that future Cerenkov light measurements in a large sample of showers, may contribute significantly towards the identification of the masses of the primary cosmic ray particles.

The problem of the origin and nature of the galactic magnetic field is of fundamental interest. The astrophysical consequences of this field are far-reaching, being particularly relevant to the unsolved problem of the origin of cosmic rays. An analysis is made of the small-scale and large-scale feature, of the distribution of arrival directions of ultra-high-energy cosmic rays in the hope of deducing information about their sources and the strength and degree of irregularity of galactic and intergalactic oiagnetic fields. The outcome of these statistical searches is negative. After a review of the basic ideas of the turbulent dynamo, techniques are developed for performing numerical experiments upon the galactic dynamo. The results of these experiments indicate that dynamo action can occur in the galaxy and a steady solution is most easily excited. The dependence of the models upon boundary conditions and relevant astrophysioal parameters is investigated. An attempt is made to simulate the nonlinear effect of suppression of turbulence by the magnetic field, which is incorporated into the model proposed for the Galaxy. The propagation of ultra-high-energy cosmic rays is examined for this . model. It is found that these particles cannot be of Galactic origin if they are protons, in agreement with the results obtained from conventional field models. Comparisons are made between the predictions of the dynamo models and the observed synchrotron radiation from the Galaxy and external galaxies which shed some light upon the nature of the intergalactic medium.

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This thesis describes an aspect of the operational and functional implementation of the CORES instrument, an electronion spectrograph to be flown aboard the Russian Obstanovka Experiment Complex mission to the ISS in 2008. For the phenomenon under investigation, wave-particle interactions in space plasma, CORES is ideally suited as it can accept a very wide band of energies simultaneously and at the same time have 3600 field-of-view. This instrument includes a novel delay-baSed particle readout system, . developed specifically for this application. A reconfigurable device (FPGA) lies at the heart of the instrument, and this has been taken fully advantage of to achieve the necessary functionality. As such this thesis mostly focuses on the configuration of this device, which allows for the multi-channel particle capturing, as well as defining the processing abilities of the instrument. These include a number of novel functions implemented in hardware for spectral analysis of the recorded particle events, such as a parallel version of se~ond order correlation, a parallel version of the I-bit autocorrelation function, etc. Furthermore, an innovative tool for on-board telemetry filtering is also presented, namely the on-board calculation of the information content of the collected measurements. This thesis also offers a technical view of CORES, presenting its capabilities based on its hardware structure.

Clusters of galaxies provide us with a sensitive probe with which to study the Universe. Their mass function is strongly dependent on the cosmological parameters, which govern the dynamical evolution of the Universe and they also provide a representative sample of ~he Universal matter distribution. The Sunyaev-Zel'dovich effect (SZE) is a promising method for detecting clusters out to their form.ation redshift and has also been shown to be a good estimator for cluster masses, A combination. of X-ray and SZE data can also be used to measure the dista:nce to the cluster, independently of the cosmic distance ladder, allowing a measurement of the Hubble Constant. However, the success of SZE methods is highly dependent on a detailed understanding of the physics of galaxy clusters. We have undertaken a multi-wavelength survey of 8 ga:laxy clusters, the Viper Sunyaev-Zel'dovich Survey (VSZS), in order to assess and highlight the issues which may be encountered by upcoming large scale SZE surveys. Such surveys will not be able to study individual clus- . ters in great detail and will be reliant on the ·accuracy of scaling relations and assumed cluster models. \Ve have therefore imaged each cluster in our sample simultar;eously at three frequencies (150GHz, 220GHz and 280GHz) with the Arcminute Cosmology Bolometer Array Receiver (ACBAR), and have followed-up with X-ray observations (Chandra and XMM-Newton) and some optical observations (Gemini), in order to carry out a detailed analysis of the cluster ICM structure. We have made some of the highest significance detections of the SZE to date. Several clusters were detected at two frequencies, as a temperature increment at 280 GHz and a decrement at 150 GHz and some of these clusters were also resolved by the observations. Most of the VSZS sample were detected as SZE signals for the first time. Although Abell 3667 and lE0657-56 had been detected previously, these were now detected at two frequencies for the first time. We have added the results of the four fully analyzed VSZS clusters to the Y- T relation of Bonamente et al. (2007) and have found our points to lie well within the scatter of the relation, except fOr cluster A3112, which has possible radio source contamination. We have also found that cluster temperatures estimated from the Y - T relation are better overall at tracing the X-ray spectral temperature than the Lx - T derived temperatures.