The evidence for the existence of a magnetic field in the Galaxy is very briefly summarised, end the importance and principle of the measurement of the Zeeman effect in interstellar neutral hydrogen clouds is discussed. The results and limiting factors of the earlier Jodrell Bank Zeeman experiments (1959 to 1961) are revieved, and the equip rental, observational and analytical techniques used in the Fourth Zeeman experiment and associated continuum and polarisation measurements, (January 1962) are described in some detail. By combining the results of the first four experiments, significant results are obtained for the magnetic field components in three absorptior. features, enabling tentative conclusions to be drawn with regard to the magnitude and direction of the magnetic field in the vicinity of the Sun. It is shown that in order to obtain mole significant results, the receiver noise performance required improvement. The progress of the low noise work at Jodrell Bank is traced, and the expected improvement in the sensitivity of the Zeeman experiment when applied to various spectral features, is calculated. The continuum, polarisation and Zeeman observations of August/ September 1962, employing a parametric amplifier at the 'front end' of the receiver, are described in detail, and the general magnetic field in the 'Orion' and 'Perseus' spiral arms is estimated. It is shown that the observations indicate a magnetic field highly variable in magnitude and/or direction, with a net field ~ 5 x 10-6 oersted directed clockwise around the Galaxy when viewed from the North Galactic Pole. other measurements and estimates of the Galactic magnetic field are reviewed and compared with the Jodrell Bank measurements. The thesis concludes with a brief discussion of the possible further work required to elucidate the problem.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:605173 |
| Date | January 1963 |
| Creators | Wild, P. A. T. |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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