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A study of the properties of transient changes in the cosmic ray intensity.


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McCracken, Kenneth G(Kenneth Gordon),1933- 1958 , 'A study of the properties of transient changes in the cosmic ray intensity.', PhD thesis, University of Tasmania.

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Three decades of research have shown that the cosmic ray
intensity varies with time. Some of the variations have been shown
to be due to atmospheric changes, while others are apparently produced
by extra-terrestrial mechanisms. It is now known that most of the
variations are small, of the order of a few percent, and that they
do not correlate simply with other geophysical phenomena. In order to
study them satisfactorily, recorders must be constructed such that the
statistical fluctuations in the observations are considerably smaller
than the cosmic ray variations themselves. It has become clear that
the only worthwhile observational programme is a long term one,
lasting for at least a number of years. A number of different types of cosmic ray detector have been
developed, among these being the ionization chamber, the geiger counter
telescope and the neutron monitor. It has been shown that comparison
of neutron monitor data with those from either of the other instruments
yields information on the manner in which the cosmic ray spectrum
varies with time. Similar information is provided by the comparison
of results obtained at high and low geomagnetic latitudes. Furthermore,
observatories at different longitudes enable the directional
dependence of the variations to be determined. Late in 1953 the University of Tasmania commenced observations
of the vertical meson intensity at Hobart using a large geiger counter
telescope. During 1954 and early 1955 the candidate, in partial
fulfilment of the requirements of the Degree of Bachelor of Science
with Honours, investigated and eliminated faults which had previously
prevented an ionization chamber from being operated successfully.
Thus by the end of 1955, the cosmic ray intensity at Hobart was being
measured by two different types of recorder.
In the latter half of 1955) I undertook to design and construct
a neutron monitor. Boron Trifluoride counters were purchased from a
commercial firm, and by June, 1956, a prototype monitor was in
operation at Hobart. In order to achieve a higher counting rate,
it was decided to site the monitor on the slopes of Mt. Wellington,
the mountain at whose foot Hobart is situated. A hut was built and
by the middle of July, 1956, the monitor had been transferred from
Hobart and was in fully automatic operation.

Item Type: Thesis - PhD
Authors/Creators:McCracken, Kenneth G(Kenneth Gordon),1933-
Keywords: Cosmic rays
Copyright Holders: The Author
Copyright Information:

Copyright 1958 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

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Thesis (Ph.D.)--University of Tasmania, 1959

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