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Simulation of Space Environment Effects On Particle Sensors
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- Author / Creator
- Rehman, Saeed ur
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This dissertation presents detailed analyses of the interaction between space plasma and satellites, and its effect on the payload sensor measurements using particle in cell (PIC) and test-particle modeling. In a satellite frame, the plasma flow velocity ~v and geomagnetic field ~B lead to a motional electric field ~E = −~v × ~B , which affects the sheath surrounding the spacecraft and the particle distribution functions in the vicinity of the sensors. Combined with the sheath electric field resulting from spacecraft charging, this can then lead to aberrations in measurements made with these sensors, particularly with those sensitive to thermal particles. As case studies, a particular attention is given to the Swarm electric field instrument (EFI). On each of the three Swarm satellites, EFI consists of a pair of thermal ion imagers (TIIs) mounted on the ram face and two small Langmuir probes extending in the nadir direction. The TIIs are capable of measuring ion distributions in three-dimensional velocity space. The centroid of the O+ ion flux on the array of detectors in these sensors, serves to determine the plasma flow velocity in the satellite rest frame, from which the motional electric field can be inferred from the relation above. At the time of this writing, no in situ validated measurements were available from the Swarm sensors, but simulation results obtained, assuming representative ionospheric parameters, indicate that aberrations associated with spacecraft charging and motional electric fields can be expected to vary in the range ±200 m/s between the North and South magnetic poles. Characteristics of the Langmuir probes are also calculated, in which the effect of the local magnetic field and the possibility of crosstalk is considered. Magnetic fields are found to have a measurable effect, despite the fact that thermal electrons have a larger gyro-radius than the probe size. Under normal conditions, no significant crosstalk between the probes is expected. In another study, the first fully kinetic quantitative estimate of magnetic field perturbations caused by the interaction of a spacecraft with space environment is made. In this case, magnetic field perturbations are below the sensitivity threshold of the on-board Swarm magnetometers. However, for missions subject to more intense solar radiation, they would likely approach or exceed instruments’ sensitivity thresholds. Finally, PTetra simulations are applied to a laboratory experiment, relevant to plasma-satellite interaction. In this experiment, the interaction of a supersonic argon plasma with a conducting sphere in a vacuum chamber is studied, and Langmuir probe characteristics are measured. Characteristics are computed at two probe locations which are in good agreement with measurements.
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- Graduation date
- Fall 2014
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- 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.