School of Physics - Theses
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ItemThe fading of HF radio waves obliquely reflected by the ionosphere( 1970)The more prominent spatial and temporal irregularities of the ionosphere, interpreted from the abnormalities manifested by ionospherically propagated HF radio signals, are reviewed in Chapter I. Some of the applications of geometrical optics and diffraction theory of this problem are then presented. This is followed by a survey of various transionospheric , as well as vertical and oblique incidence, reflection investigations of the fluctuation of intensity (fading) of radio waves and the information derived there from concerning both the ionospheric irregularities and the structure of the radio wavefield at the ground. ...
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ItemThe application of variational techniques to radio propagation in the ionosphere( 1971)Radio rays are introduced as curves playing a vital role in a short wavelength solution of the equations governing radio propagation in the ionosphere. Taking advantage of the variational equations satisfied by the rays, expressions are found for the variations of the phase path and a number of related quantities due to changes in the ionospheric medium or ray endpoints. The results are applied to the study of group propagation, Doppler shifts, Faraday fading, direction finding, power flow and ray reciprocity.
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ItemThe vertical distribution of ozone and atmospheric circulation( 1963)In 1845 Schönbein proposed that ozone might be a constituent of the atmosphere. Observations of the cut-off of the solar spectrum in the ultra-violet led Cornu to suggest in 1978 that the cut-off was due to absorption in the earth's atmosphere. Hartley (1880) discovered absorption bands of ozone extending from 2100 A.U. to 3200 A.U., which he correctly suggested were responsible for the cut-off at about 2900 A.U. The discovery by Huggins (1890) of absorption bands in the spectrum of Sirius, and their identification with ozone absorption in the terrestrial atmosphere by Fowler and Strutt (1917) confirmed Hartley's suggestion. When Wigand (1913) photographed the solar spectrum from a height of 9 km. he found practically the same cut-off as at sea level, indicating that the ozone is situated above this altitude. Measurement of the ratio of the intensities of a wavelength in the near UV for varying zenith angles of the sun led Fabry and Buisson (1912) to conclude that the ozone in the atmosphere is equivalent to a layer about 2 to 3 mm. thick at STP situated at about 50 km. altitude. Strutt (1918) and Cabannes and Dufay (1925) found similar results. Dobson and Harrison (1926) refined the method due to Fabry and Buisson (see Chapter 2.4a), and pioneered a worldwide network of observation stations to determine latitudinal, seasonal, and meteorological variations in the total ozone amounts. (From Ch.1 Introduction)