Hybrid-Kinetic Modelling of Space Plasma with Application to Mercury

  • Author / Creator
    Paral, Jan
  • A planet's magnetosphere is often very dynamic, undergoing large
    topological changes in response to high speed (~400 km/s) solar wind
    intervals, coronal mass ejections, and naturally excited plasma wave modes.
    Plasma waves are very effective at transporting energy throughout the
    magnetosphere, and are therefore of interest in the context of the coupling
    between solar wind and magnetosphere. Of relevance to this thesis is
    Kelvin-Helmholtz macro-instability. Kelvin-Helmholtz instability (KHI) is
    excited by shear of the flows. KHI is commonly observed at equatorial
    regions of the magnetopause where fast flowing magnetosheath plasma may
    interact with slow bulk velocities of magnetospheric plasma. The instability
    is responsible for exciting shear Alfv'en waves which (at Earth) may be
    detected using the ground based magnetometers located at latitude of excited
    field lines. This thesis uses numerical modelling to understand and to
    explain the generation and propagation of the KHI in Mercury's magnetosphere.
    The instability is initiated close to the planet and convectively grows while
    being transported along the tail. When the wave amplitude reaches a
    nonlinear stage, the structure of the wave becomes complex due to the
    wrapping of the plasma into the vortex. A vortex structure is typical for
    KHI and it is used for identifying the wave in the data from satellites. The
    instability commonly occurs at the dawn or dusk flank magnetopause (MP) of
    Earth with approximately the same probability. But the data from NASA's
    MESSENGER spacecraft, currently in the orbit of the planet Mercury, suggest a
    strong asymmetry in the observations of KHI. It is shown that the KHI
    initiated near the subsolar point evolves into large-scale vortices
    propagating anti-sunward along the dusk-side MP. The simulations are in
    agreement with the third flyby of the MESSENGER spacecraft, where saw-tooth
    oscillations in the plasma density, flow, and magnetic field were observed.
    The observed asymmetry in the KHI between dawn and dusk is found to be
    controlled by the finite gyro-radius of ions, and by MP pressure gradients
    and the large-scale solar wind convection electric field.

  • Subjects / Keywords
  • Graduation date
    Spring 2013
  • 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
    • Heimpel, Moritz (Department of Physics)
    • Bowman, John C. (Department of Mathematical and Statistical Sciences)
    • De Sterck, Hans (Department of Applied Mathematics)
    • Sydora, Richard (Department of Physics)