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

  • Planet Mercury
  • Numerical Modelling
  • Magnetosphere

• Graduation date

  Spring 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3GB0N

• 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.