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Magnetosphere-Ionosphere Coupling During Substorms
- Author / Creator
- Murphy, Kyle R
This thesis concerns the development and evolution of the magnetospheric substorm. In
particular this thesis concentrates on the dynamics of Ultra Low Frequency (ULF) waves
during the substorm growth and expansion phases, the coupling of the ionosphere and
magnetosphere through substorm onset and the substorm expansion phase and the
location in the magnetosphere and physical processes leading to substorm onset.
Firstly we present a superposed epoch analysis of ULF waves through the substorm
growth and expansion phase, characterizing the two dimensional distribution of power
spectral density and polarization of these waves with respect to auroral onset. We
demonstrate that ULF wave power during substorms is characteristic of a power law and
that the distribution of wave power and polarization is consistent with the expected
pattern in the presence of a substorm current wedge.
Secondly we examine the global field aligned current (FAC) morphology through the
substorm growth and expansion phase. We demonstrate, for the first time, that there is
a clear reduction in FACs coupling the ionosphere and magnetosphere just prior to
substorm onset. We suggest that this change in coupling may play an important role in
the destabilization of the magnetosphere at substorm onset. We also present the first
two‐dimensional in‐situ observation of the FACs and ionospheric current sheets
comprising the substorm current wedge in the substorm expansion phase. We
demonstrate that the structure of the substorm current wedge is significantly more
complex than the classical view of the substorm current wedge.
Finally we present a comprehensive ground and in‐situ analysis of two substorms to
determine where in the magnetosphere the substorms initiate. We demonstrate that both substorms initiate on closed field lines in the inner magnetosphere. More
significantly we demonstrate that magnetic reconnection can follow substorm onset and
that earthward magnetotail flows or auroral streamers, their ionospheric counterparts,
are not a necessary condition for substorm onset.
- Graduation date
- Spring 2014
- Type of Item
- Doctor of Philosophy
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.