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.

• Subjects / Keywords

  • Magnetosphere-ionosphere coupling
  • Aurora
  • Substorms

• Graduation date

  Spring 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R38K75505

• License

  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.