MF radar interferometry

This thesis describes the development, operation and observations of interferometry experiments on two medium frequency spaced antennae radar operated by the Department of Physics and Astronomy of the University of Canterbury; the 2.4 MHz radar at Birdlings Flat near Christchurch, New Zealand, and the 2.9 MHz radar at Scott Base on Ross Island in the Antarctic. These radars are of a standard design and detect scattering from the D and lower E regions of the ionosphere in the mesosphere and lower thermosphere. The interferometry techniques used were those of temporal, spatial and frequency domain interferometry which provide information on Doppler shifting and the directional and radial distribution of backscattered signals received by the radars. This project represents the first time that these techniques have been operated together on radars of the type used in this project. The techniques were also carried out in conjunction with the standard procedures used on these radars, that of Spaced Antennae Drifts with Full Correlation Analysis (FCA). Various forms of interferometric analyses were carried out and comparisons were made between the results of interferometric analyses and those of more conventional techniques. For example a study was made of the relationship between interferometric and FCA velocities in which it was found that there was good agreement between the two methods, particularly when the scattering region does not change rapidly as it moves. Other analysis techniques investigated included examination of the angular distribution of scattering and aspect sensitivity, the statistical distributions of scattered signals, post beam steering, vertical velocities and momentum fluxes. Frequency domain interferometry provided enhanced measurement of range and the scattering depth or distribution of range of scattered signals. Measurements of scattering depth clearly identified examples of thin layers or localized scatter. These localized scattering events appeared to be associated with either steady flow or long period variations in steady flow, for example with the semidiurnal solar tide. Aside from these events much of the scatter was observed to be anisotropic and also appeared to originate from a number of distributed scattering centres spread horizontally and vertically in a manner consistent with Fresnel scattering models

High resolution radio continuum survey of M33: I. The radio maps

We study the exponential scale length of total radio emission, the spectral index distribution, and the linear radio polarization in the Scd galaxy M33. Observations were carried out using the 3.6 cm dual channel and the 6.2 cm four channel receivers of the 100--m Effelsberg telescope along with the L-band VLA D--array at 20 cm. High spatial resolution and sensitivity in both total and linearly polarized radio continuum emission from M33 were achieved. We found considerable extended emission, not only from the main arms I S and I N, but also from the weaker arms. The large--scale magnetic field exhibits well--ordered spiral structure with almost the same orientation as that of the optical spiral arms, however, it does not show a clear structural correlation or anti--correlation with the optical arms. There is a north-south asymmetry in polarization that is frequency-dependent. We found that the ring mean spectral index versus radius increases faster beyond $R$ = 4 kpc. At each wavelength, the exponential scale length is larger inside than outside $R$ = 4 kpc. From the larger scales lengths at $R$ $<$ 4 kpc, we conclude that star forming regions are mainly spread over the region $R$ $<$ 4 kpc without a dominant nuclear concentration. Furthermore, at $R$ $<$ 4 kpc, a spatial correlation between cosmic rays and star forming regions may exist. From the behaviour of the mean spectral indices obtained from different pairs of the radio continuum data at 3.6, 6.2, and 20 cm, we confirm that a decrease in the thermal fraction causes an increase in the spectral index. The frequency-dependent asymmetry in the polarization hints to an asymmetry in Faraday depolarization.Comment: 16 pages, 13 figures, accepted for publication in the Astronomy and Astrophysics Journa

Natural law and religion in the thought of Samuel Pufendorf (1632-1694)

The emergence of natural law in seventeenth-century Europe was a response to decades of continuous "Warre" inspired by religious differences. The natural jurists of the seventeenth century (Grotius, Hobbes, and Pufendorf) all sought a remedy for the condition of war in independent sovereign states. Pufendorf's concept of a state derived from an assumed natural state of mankind, regulated by a law of nature, a law which obliges all men to be sociable, and agree upon the means of achieving sociability, namely contractual submission to sovereign power. Pufendorf developed his major work, De Jure Naturae et Gentium, as a synthesis of Grotian and Hobbesian thought, making sociability the foundation of his natural law system. This earned him the criticism, that he had effected a heretical separation of natural law from theology. Pufendorf responded to this accusation with a work on church-state relations and in De habitu religionis christianae ad vitam civilem, he reinforced his view concerning the role of the church as a necessary institution for the moral education of the citizen, but under the jurisdiction and protection of the civil authority. Late in his life, Pufendorf admitted that natural law could only provide the mere necessities of sociability, but that for the fulfillment of mankind the observation of religious dictates of a moral theology was necessary. And to know these, in addition to common sense, faith in theology, as revealed in Holy Scriptures is needed. His last work, Jus Feciale Divinum sive de Consensu et Dissensu Protestantium, was concerned with the fundamental articles of faith necessary for Salvation, and the common ground for a Christian morality, as a possible means of uniting all religious denominations. His legitimate notion of individual state sovereignty, so necessary for his time in defence against the imperialist forces of secular as well as ecclesiastical domination, has now become the very obstacle to the necessary reunification of nations under the dictate of pressing global concerns. However, his theological jurisprudence, inspired by Christian belief, can contribute to the unification of all religious denominations into a single source of humanism. To this end, Pufendorf had made a valiant contribution, hitherto unrecognized, which this thesis attempts to correct