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Die effek van aurorastrukture op die absorpsie van kosmiese radioruis gedurende Junie 1982

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dc.contributor.author Coetzer AG en
dc.date.accessioned 2016-09-22T07:18:16Z
dc.date.available 2016-09-22T07:18:16Z
dc.date.submitted 1988 en
dc.identifier.uri http://hdl.handle.net/20.500.11892/12568
dc.description.abstract The aim of this study is to look at the effect of auroral structures on the absorption of cosmic radio noise using absorption data from riometers recording cosmic radio noise at 20, 30 and 51,4 MHz at Sanae, Antarctica (L=4,0). <br><br> Of special interest is the so-called "spike event", in which impulsive electron precipitation produces a sudden increase in the absorption of cosmic radio noise followed by a rapid return to a less disturbed level. An absorption spike is caused by a ribbon-shaped enhancement in the ionospheric electron density causing maximum absorption at an altitude near 90 kilometres. <br><br> The measured absorption, using the Appleton-Hartree treatment for radio waves crossing the ionosphere, was calculated.-The frequency dependence of the riometer absorption is represented by a power law of the frequency: A(f) = C.f <sup>-n</sup>, and values-for n are determined from the calculated absorptions. <br><br> A method is discussed whereby interferences on the riometer recordings are filtered from the data. Quiet day curves are obtained by the super-position of successive riometer recordings with a period of one sidereal day. A Fourier series is fitted to the points of maximum density to represent the quiet day recordings. <br><br> An absorption event on day 164 (1982) is treated as a spike event and analyzed with a time resolution of 2 seconds for the 30 MHz riometer. The calculated velocity, width and length of the ribbon are in the order of 400 m/s, 28 kilometres and 250 kilometres respectively. <br><br> Absorption events on day 178 (1982) are analyzed with a time resolution of 4 minutes for each riometer frequency. When ionospheric irregularities scatter cosmic radio noise from the more luminous parts of the radio sky into the riometers field of view in addition to the non-deviative radio flux, the recorded auroral absorption wil be strongly frequency dependent. The absorption is much more reduced at 20 MHz than at the higher riometer frequencies. This reduced absorption at 20 MHz was observed for the absorption event recorded at Sanae at 0122 UT on 27 June 1982. en
dc.language Afrikaans en
dc.subject Physics en
dc.title Die effek van aurorastrukture op die absorpsie van kosmiese radioruis gedurende Junie 1982 en
dc.type Masters degree en
dc.description.degree MSc en

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