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Pulsating aurora and magnetic Pi(c) pulsations
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Abstract
This thesis is the result of a year spent at Macquarie Island
(54° 30'S, 158°57'E) on the 1983 Australian National Antarctic
Research Expedition, collecting data pertaining to pulsating
aurora and geomagnetic Pi(c) micropulsations.
Data was collected with a 0.2s sampling period and stored by an
LSI-11 microcomputer on floppy disks for the bulk of the year, then
on RLO2 hard disk for the final months. Strong peak-to-peak
correlations were observed between the optical pulsating aurora,
measured at the N2+ 4278A band head emission, and the micropulsations.
Average time delays were determined to be 0.6s and 0.3s for the D and
H Pi(c) micropulsations respectively, trailing the optical fluctuations.
The H component Pi(c) micropulsations will be shown to be
consistent with a precipitation induced Hall conductivity enhancement
of the westward E-region auroral electrojet during the greater part of
this activity. The sign, or phase, of the 4278A/H micropulsation
correlation function was in close agreement with the large scale magnetogram
H component perturbation.
The D component Pi(c) have in the past been interpreted as either
an E-region Pedersen conductivity induced variation, or a direct field
aligned current effect. Their correlation sign, or phase, is shown
to be not in accord with the large scale D component magnetograms
which are known to be effected by other than E-region currents, namely
the field aligned fluxes." The D micropulsations are more frequently
correlated at an acceptable level with the optical emission, and
their correlations are in general of greater magnitude than those of
the H Pi(c).
Experimentally observed lack of a frequency doubling in the
micropulsations with respect to the optical trace, occasional phase
reversals of the correlations, and the delay sequence, wherein the
optical pulses predominantly lead the H micropulsations, which in
turn generally lead the D component, can all be reasonably explained
in terms of the above theories.
A model has been developed, involving rotations of the total
ionospheric electric field, which makes basic predictions concerning
the phases of the correlations, and the lead-lag relationship between
the micropulsation components. These predictions are borne out by
the data set, specifically during phase reversals, and strongly indicate
that the H and D Pi(c) micropulsations result from precipitation
induced conductivity fluctuations in E-region current systems.
Item Type: | Thesis - Unspecified |
---|---|
Authors/Creators: | Craven, M.(Michael) |
Keywords: | Auroras, Geomagnetic micropulsations |
Copyright Holders: | The Author |
Copyright Information: | Copyright 1985 the Author - The University is continuing to endeavour to trace the copyright |
Additional Information: | Thesis (M.Sc.)--University of Tasmania, 1985. Bibliography: leaves 216-226 |
Item Statistics: | View statistics for this item |
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