Doctor of Philosophy
Campbell-Brown, Margaret D.
Small, faint meteors (with masses between 10-7 and 10-4 kg) were once part of an asteroid or comet, and collide with Earth's atmosphere daily. Studying meteors is an effective way to survey the physical properties of their parent bodies. Meteor light curves and orbital information is easily obtained from wide-field observations, from which meteoroid structure can be inferred through meteoroid ablation modelling. A high-resolution narrow-field camera can provide much more detail about the poorly understood ablation processes and physical properties of the meteoroid. The goal of this thesis is to better understand the physical properties of meteors using high-resolution optical observations.
In the first part of this work, wide-field and narrow-field optical observations of faint meteors were combined to determine what relationships, if any, exist between meteor light curve shapes, orbits, and fragmentation behaviour. Most meteors were found to have symmetric light curves, show fragmentation in the form of a long trail, and come from cometary bodies. More than 90% of meteors observed with the high-resolution camera system showed some form of fragmentation. Unexpectedly, the dynamically asteroidal meteoroids fragmented as often as the dynamically cometary meteoroids, suggestive of dynamical mixing or contamination.
In the second part of this work, the luminous efficiency (the fraction of kinetic energy used for visible light production) of meteors was investigated. It is crucial for determining meteoroid mass, and past results vary by up to two orders of magnitude. An attempt at determining luminous efficiency through the classical ablation equations was made, and verified on simulated meteor data, while quantifying the uncertainty in the method. This was then applied to fifteen real meteor events, observed with the Canadian Automated Meteor Observatory. This is the first study which compares photometric and dynamic meteoroid masses to determine luminous efficiency, with modern high-resolution observations. Twelve of the meteors had luminous efficiency values less than 1% (agreeing with the lower end results of past studies), and there was no obvious trend with speed. A weak negative trend was observed with meteoroid mass, implying that smaller meteoroids radiate more efficiently.
Subasinghe, Dilini, "Physical Properties Of Faint Meteors Through High-Resolution Observations" (2017). Electronic Thesis and Dissertation Repository. 5077.