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Solar radio emissions.

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Yip, Wan Kwan (1970) Solar radio emissions. PhD thesis, University of Tasmania.

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Abstract

All radiation processes described can take place in
the solar corona, depending on different physical characters of
the radiating electrons and the coronal plasma, such as
electron energy, electron pitch angle and the magnitude of the ratio f-2p/f-2H of the medium in the region where the radiators
reside. On the other hand, the observed spectral features of
a solar radio emission are determined by both the mechanism
responsible for the emission and the propagation conditions of
electromagnetic waves in the solar corona. Thus, the observed
dynamic spectra of the solar radio emissions reveal essentially
the physical conditions of the solar corona during the emission periods.
The emissions of narrow bandwidth type III bursts and
drift pair bursts have been proposed as the consequence of plasma
radiation caused by electron streams in the isotropic corona,
which is understood to refer to electromagnetic radiation
extracted from Cerenkov plasma waves through scattering or wave-mode
coupling (Ginzburg and Zheleznyakov, 1958; Roberts, 1958;
Wild et al., 1963; Zheleznyakov, 1965). However, many
observed spectral characteristics of the type III bursts and its
related U bursts, the drift pairs and the newly discovered hook
bursts clearly indicate that it is necessary that the sunspot
magnetic field be taken into account in the theories. So far
the conditions of plasma radiation by electron streams in a
magnetoactive plasma have not been investigated in detail
and consequently, many characteristics of these emission events
remain unexplained. In this thesis, we begin by formulating
the theory of plasma radiation in a magnetoactive plasma
(Chapter II and Chapter V). The theory is then applied to the
interpretation of the polarized type III burst and U burst
emission event and the drift pair and hook burst emission event
in Chapter VI and Chapter VII respectively.
The origins of various components of the complicated type
IV emission have been interpreted as the results of synchrotron
radiation by relativistic electrons trapped in the sunspot
magnetic field configurations (Boischot and Denisse, 1957;
Takakura and Kaip 1961; Kai, 1964; etc.). However, without
taking into account the effects of the medium on the radiation
process, previous theories encounter various difficulties and
fail to account for the outstanding polarization characters of
the type IV emission. In order to set up a satisfactory
theory of type IVA emission, we study, for the x-mode and the
o-mode, the power spectra from single electrons, the process of
amplification of cyclotron radiation in a stream-plasma system
and the escape conditions in detail in Chapter III and Chapter
VIII. Cyclotron radiation of electromagnetic waves in the
x-mode and the o-mode and the Cerenkov excitation of plasma
waves by helical electron streams moving at the base of the
solar corona is proposed as the origin of the type IVA
emission. It is found that most of the important characteristics
of the emission can be well accounted for by the theory.
In Chapter IX, coherent synchrotron radiation from a
system of relativistic electrons is studied taking into account
the effects of the ambient plasma. The origins of some broad
band solar continuum emissions are also discussed.
In the final chapter, a conclusion of the thesis is given
and further researches are suggested.

Item Type: Thesis (PhD)
Keywords: Solar radiation
Copyright Holders: The Author
Copyright Information:

Copyright 1970 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).

Additional Information:

Thesis (Ph.D.) - University of Tasmania, 1970. Bibliography: p. 369-382

Date Deposited: 04 Feb 2015 23:18
Last Modified: 24 Aug 2016 04:10
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