Generation of Electromagnetic Ion Cyclotron (EMIC)Waves in a Compressed Dayside Magnetosphere

  • Author / Creator
    Usanova, Maria
  • Electromagnetic Ion Cyclotron (EMIC) waves are believed to play an important role in the dynamics of energetic particles (both electrons and ions) trapped by the Earths magnetic field causing them to precipitate into the ionosphere via resonant interaction. In order to incorporate the EMIC-related loss processes into global magnetospheric models one needs to know solar wind and magnetospheric conditions favourable for EMIC wave excitation as well as the localization of the waves in the magnetosphere. EMIC waves are generated by anisotropic (Tperp/Tpara > 1) ion distributions. Generally, any process that leads to the formation of such distributions may be responsible for EMIC wave initiation. This thesis discusses magnetospheric compression as a new principal source of EMIC wave generation in the inner dayside magnetosphere. First, using ground-based and satellite instrumentation, it is shown that EMIC waves are often generated in the inner dayside magnetosphere during periods of enhanced solar wind dynamic pressure and associated dayside magnetospheric compression. The compression-related EMIC wave activity usually lasts for several hours while the magnetosphere remains compressed. Also, it is demonstrated that EMIC waves are generated in radially narrow (1 Re wide) region of high plasma density, just inside the plasmapause. Test particle simulations of energetic ion dynamics performed for this study confirmed that anisotropic ion distributions are generated in the compressed dayside magnetosphere, the temperature anisotropy being dependant on the strength of magnetospheric compression. It is found that in the inner magnetosphere these anisotropic particle distributions are formed due to particle drift shell-splitting in an asymmetric magnetic field. Finally, the generation of EMIC waves was studied self-consistently using a hybrid particle-in-cell code in order to determine whether the degree of anisotropy estimated from the test particle simulations is sufficient to produce EMIC waves like those detected and to explain some of the observed wave properties.

  • Subjects / Keywords
  • Graduation date
    Fall 2010
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • 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
  • Institution
    University of Alberta
  • Degree level
  • Department
  • Supervisor / co-supervisor and their department(s)
  • Examining committee members and their departments
    • Brian J. Anderson (Applied Physics Laboratory, The Johns Hopkins University, Laurel, Maryland, USA)
    • Frances R. Fenrich (Physics)
    • Carlos F. Lange (Mechanical Engineering)