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Pulsating aurora and magnetic Pi(c) pulsations


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Craven, M.(Michael) 1984 , 'Pulsating aurora and magnetic Pi(c) pulsations', Unspecified thesis, University of Tasmania.

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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
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 (M.Sc.)--University of Tasmania, 1985. Bibliography: leaves 216-226

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