Meteoric diffusion studies of middle atmospheric dynamical structure
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
This work investigates the use of ambipolar diffusion coefficients determined by the decay times of meteors detected by the University of Canterbury's meteor radar, AMOR, in determining dynamical parameters for the middle atmosphere. The radar system has the ability to accurately determine the geometric altitude of detected meteor trains, thereby making it a potentially powerful tool for detailed and continuous observation of the atmosphere. Software has been developed in the IDL interpretative language to analyse the data in two main ways. Firstly a brief analysis of the relationship between geometric altitude and ambipolar diffusion coefficient was made. As with all previous work the logarithmic relationship predicted between the two was confirmed on average, although a very large degree of true scatter was found. The density scale height inferred by this analysis was found to be in reasonable agreement with recent previous results. The major part of the analysis done used the ambipolar diffusion coefficient as a measure of temperature change and investigated these changes over time. Three time scales were investigated; variations over a few hours, daily behaviour and long term change over months and years. All three scales showed evidence of time dependent structure. The short time scale analysis showed evidence of fluctuations consistent with gravity wave propagation. Mid time scales showed a diurnal oscillation, but the source of this is unclear. Long time scales showed an annual variation in agreement with the broad temperature structure of the middle atmosphere.