Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Physics

Supervisor

Dr. J.-P. St.Maurice

2nd Supervisor

Dr. R. J. Sica

Joint Supervisor

Abstract

The closure of magnetospheric currents in the high latitude ionosphere makes the
high latitude thermosphere a very dynamic environment. The composition and dynamics
of this region become even more complex during geomagnetic disturbances
as the electric fields from the magnetosphere now have the ability to substantially
alter the winds and composition of this region. This complexity is especially apparent
in mass spectrometer observations of composition changes, with heavier gases
(N2,O2, andAr) showing substantial enhancements while lighter gases (He and O)
normally exhibit moderate to severe depletions. Quantifying the changes in atomic
and molecular oxygen can be particularly difficult as most mass spectrometers are
not able to discern between ambient molecular oxygen and the molecular oxygen created
by atomic oxygen-satellite surface interactions - one usually measures the total
oxygen content O + 2O2 and assumes that any molecular oxygen above 250 km is
due to the recombination of atomic oxygen on a satellite surface. High resolution
simulations presented in this thesis suggest that large amounts of molecular oxygen
can be transported upwards by vertical winds during geomagnetic storms and that
the neglect of this transport effect will lead to substantial overestimations of atomic
oxygen number densities by mass spectrometers at higher altitudes. These overestimations
can be quite significant; a simulated total oxygen depletion of one-half at 280 km could mean that the atomic oxygen number densities at 280 km are actually one-seventh of their normal values while the simulated molecular oxygen concentrations are 25 times larger than normal.

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