Numerical study of ionospheric response to perturbations and interaction with spacecraft instruments

• Author / Creator

  Imtiaz, Nadia

• This PhD thesis presents numerical studies of the ionosphere dynamics and of the interaction between ionospheric plasma and spacecraft instruments.
  The main results of my research are the following:
  A first study presents a simple model to account for magnetic field perturbations in response to geophysical phenomena such as earthquakes.
  Following an earthquake, large neutral density and velocity perturbations reach altitudes of $ 150-350 $ km, where significant coupling between the neutral atmosphere and the ionosphere occurs.
  Photoionization and collisional friction between plasma and the neutral exosphere then results in a rapid variation in ionospheric plasma parameters.
  This in turn leads to the generation of two types of waves: shear Alfv'en and the compressional modes.
  Variations in the total electron content (TEC) are also computed for the ion acoustic mode and the compressional mode by considering density perturbations along and transverse to the magnetic field.
  The second part of my work considers the interaction between ionospheric plasma and spacecraft instruments under different plasma conditions.
  This is achieved by simulating space plasma interaction with two different particle sensors; namely, DEMETER's Segmented Langmuir probe (SLP) and JOULEII Suprathermal Ion imager (SII).
  The current characteristics of the SLP are computed with particle in cell (PIC) code, under different plasma conditions.
  The current collected by each segment varies with the orientation of the plasma flow velocity, the plasma composition and with the orientation of the magnetic field.
  For validation of the simulations, the computed characteristics are compared with DEMETER in situ measurements.
  Simulation results are found to be in good agreement with measurements.
  Finally, the impact of plasma flow on ion velocity distributions in the vicinity of the SII sensor aperture is numerically investigated.
  It is observed that the plasma flow modifies the electrostatic sheath and affects the velocity distributions of $NO^+$ and $O_2^+$ ions at the aperture of the SII sensor. The velocity distribution functions at the SII aperture are used to compute ion fluxes on the SII micro channel plate (MCP) and computed fluxes are compared with JOULEII measurements.

• Subjects / Keywords

  • Suprathermal Ion Imager
  • Ionospheric perturbations
  • Langmuir probes

• Graduation date

  Spring 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3FB4WV38

• 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.