M. L. Duldig
, PASA, 18 (1), in press.
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Title/Abstract Page: Australian Cosmic Ray Modulation
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The Early Years
Much of the cosmic ray literature in the 1930's discussed the East-West effect that had been discovered with a two tray Geiger Müller telescope (see Duldig 1994 for a description of cosmic ray telescopes). An asymmetry had been found in the response at the geomagnetic equator of 15% (total intensity) to 30% (hard component) at 45o zenith angle with the maximum response arriving from the west and minimum from the east. This was correctly interpreted as arising because the majority of the cosmic rays were positively charged and probably protons (Johnson & Street 1933; Johnson et al. 1940; Johnson 1941). Seidl (1941) had shown that there was a much smaller East-West asymmetry at the higher magnetic latitude of 54o N at New York. His measurements indicated a statistically significant value somewhat smaller than 1%. Geoff Fenton saw this as a measurement that could be repeated from Hobart at a similar southern geomagnetic latitude of 52o. Geoff Fenton and D.W.P. (Peter) Burbury constructed a 2 tray Geiger Müller telescope on a turntable and with adjustable zenith angle of view. The results, which demonstrated that the southern hemisphere asymmetry was identical to that observed by Seidl in the north, were submitted to Physical Review for publication in April 1948 and were published in September of the same year (Fenton & Burbury 1948). This was the first cosmic ray research project of the group and formed the basis of Peter Burbury's PhD studies (Burbury 1951). Peter Burbury later received the second PhD awarded by the University of Tasmania. Next Section: Establishing the Australian Network
Title/Abstract Page: Australian Cosmic Ray Modulation
Previous Section: Introduction
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