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ULF Waves in the Magnetosphere and their Association with Magnetopause Instabilities and Oscillations

  • Author / Creator
    Nedie, Abiyu Z
  • This thesis addresses the question of excitation of ULF waves by magnetopause instabilities and oscillations. Given proper spacecraft orientations and near magnetopause encounters, the CLUSTER spacecraft mission is used to resolve the space-time ambiguity inherent in a single spacecraft measurements. A case study is presented where a driver ULF wave is identified in the solar wind and on open field lines in association with a Field Line Resonance (FLR). This is one of the rare examples where a solar wind source has been unambiguously identified and causally linked with excitation of a FLR at the same frequency. It adds to a database of observations that can be used to determine the statistical relationship between various sources of ULF plasma waves and FLRs. It is also one of the few observations of a driver wave on open field lines by SuperDARN, and encourages further use of SuperDARN in that regard. In the second case study, a ULF wave signature at 1.7 mHz is observed just outside the magnetopause using CLUSTER and compared with fluctuations at ionospheric altitudes and on the ground. It is shown that ULF fluctuations at the magnetopause coincide with discrete frequency oscillations in HF radars, magnetometers and spacecraft inside the magnetosphere. The Poynting vector and phase propagation outward from the magnetopause, and the absence of a source in the solar wind, suggest a KHI generated surface mode as a source mechanism. A third case study presents a magnetopause oscillation resulting from a direct solar wind driver that transfers energy from the solar wind into FLRs. We observe a quasi-monochromatic 2.5 mHz discrete wave oscillation in IMF By. The dusk signature of the wave shows magnetic field and plasma flow oscillations at the magnetopause at the same discrete frequency. The SuperDARN Saskatoon radar in the pre-dawn sector reveals the footprint of an FLR structure with anti-sunward phase propagation that is linked to the solar wind driven magnetopause oscillation. This is the first work using SuperDARN that relates a solar wind driven magnetopause oscillation with a discrete frequency FLR in the magnetosphere. The thesis concludes by presenting results from a 2D ideal MHD wave model that is successful in qualitatively reproducing observed structure of FLRs for both KHI-like drivers and solar wind-driven magnetopause oscillations.

  • Subjects / Keywords
  • Graduation date
    2012-09
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/R31620
  • 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.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Doctoral
  • Department
    • Department of Physics
  • Supervisor / co-supervisor and their department(s)
    • Rankin, Robert (Physics)
    • Fenrich, Frances (Physics)
  • Examining committee members and their departments
    • Tsui, Ying (Electrical Engineering)
    • Koustov, Sasha (Physics), University of Saskatoon
    • Fenrich, Frances (Physics)
    • Sydora, Richard (Physics)
    • Rankin, Robert (Physics)