Aurora and associated VLF phenomena.
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Date
1978
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Abstract
Observations have been made at Sanae (gm. lat. -63,71°) on
occurring auroral forms, (diffuse and pulsating aurora), and
simultaneous occurring VLF phenomena, (whistlers and auroral hiss) .
Two studies are presented in this thesis.
(a) A comparison of the positions of auroral forms and the
positions of field lines, along which whistlers propagate, is made and it is found that:
(i) Diffuse aurora occurs on closed field lines and indirect evidence shows that this is also the case for pulsating aurora.
(ii) For two periods of data the separation of diffuse
aurora from the plasmapause ranges from < 0,9 L
to < 0,2 L but during a third period, the diffuse
aurora lies, at least partially, within the plasmasphere.
(b) An investigation into the association between pulsating
aurora and pulsating auroral hiss is made and it is
shown that:
(i) A common identical pulsation period of 0,75 s and
high coherency exists between the light intensity
of an auroral patch and the intensity of the associated
pulsating auroral hiss. This suggests a wave-particle
interaction as a common modulation mechanism.
(ii) Cyclotron instability (gyroresonance) or Cerenkov
radiation mechanisms occurring in the equatorial
plane do not account for the time delays, typically
between 0,90 s and 0,157 s, found to be present between,
the two phenomena, where the incident auroral electrons,
responsible for the auroral patch light intensity,
are observed to arrive before the auroral hiss
emissions.
The results of the analysis in (a) are reported in The Journal
of Atmospheric and Terrestrial Physics, 39, 1429, 1977.
Description
Thesis (Ph.D.)-University of Natal, 1978.
Keywords
VLF emissions., Auroras., Whistlers (Radio Meteorology), Theses--Physics.