Field Line Resonances in Earth’s Magnetosphere: A study of their Observation, Characterization and Wave Sources in the Solar Wind

• Author / Creator

  Mazzino, Maria L P

• This thesis is an observational study of field line resonances (FLRs), between 0.5-5 mHz, in the Earth’s magnetosphere, and their correlation with Ultra Low Frequency (ULF) waves in the solar wind. The mechanisms for these phenomena are not yet completely understood and there is still great debate on the causes of Field Line Resonances as well as the discrete and repetitive nature reported by some studies. Many studies of FLRs have been reported, in the past decades, and recent work has indicated that discrete, continuous ULF waves in the solar wind may be responsible for driving these FLRs giving rise to particular “magic frequencies” (1.3, 1.9, 2.6 and 3.4 mHz). The premise of this study was that “magic frequencies” existed and the intent was to test the hypothesis that discrete ULF waves in the solar wind directly driving them. We successfully created an efficient algorithm and computer code to automatically detect ULF coherent waves over a large area within the field of view (FoV) of any Super Dual Auroral Radar Network (SuperDARN)’ station that could be later categorized as a “Field Line Resonance”. A total of 121 FLRs were identified during 2003 and their primary characteristics were obtained. For the 121 FLRs found in this study, ‘magic frequencies’ were not predominant in the general distribution. The frequency with more occurrences was the first in the array, 0.6±0.1 mHz. The observation of other frequencies showed a decreasing trend of observation of occurrences for increasing frequency. Results also showed deviations from the classification of FLRs by their azimuthal wavenumber m (high-m vs. low-m) provided by previous studies, in terms of their phase variation vs. magnetic latitude, propagation (sundwards-antisunwards; eastwards-westwards) and location. From the FLRs identified in this study we were not able to classify them into the two distinct groups, based upon the FLR’s azimuthal wavenumber m, but rather the classification involved many other variables. Possible alternative classifications that better adjust the observations in this study include the distinction of FLRs detected during quiet or active geomagnetic times, FLRs located either in or out of the plasmapause region, and classification of FLRs as low-m, intermediate-m, and high-m. Finally, we applied four different, complementary techniques to evaluate the coherence between ULF waves in the solar wind, detected by the Advanced Composition Explorer (ACE), and the FLRs found in this study. We found that some specific magnetospheric configurations (such as uniform plasma distribution in the flux tubes or previous excitation of the magnetosphere at the driven frequency) might play an important role in the mechanisms driving the FLRs. Additionally, mechanisms other than ULF waves in the solar wind might be involved in driving the FLRs, such as pre-existing wave packets in the solar wind matching the natural frequency of the flux tube with specific magnetospheric configurations that allow the solar wind to drive the FLRs.

• Subjects / Keywords

  • Magnetospheric Physics
  • Ultra Low Frequencies
  • Field Line Resonances

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3416T70S

• 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.