OBSERVATIONAL AND THEORETICAL STUDIES OF MESOSPHERIC DYNAMICS AND BORES USING AIRGLOW IMAGERS AT MID-LATITUDES
Loughmiller, Pamela Jane
This dissertation focuses on the study of coupling-dynamics in the mesosphere. Interesting airglow phenomena -- primarily internal bores occurring mid-latitude at mesospheric altitudes -- have been observed and studied in a multifaceted approach, combining the analysis of experimental data with modelling and theory. After the initial mesospheric bore sighting by the scientific community in 1993, the next recorded events were observed by Cornell University. To gain additional insight, this investigation effectively pursued more data by installing imaging equipment as part of a collaborative, multi-instrument campaign involving lidar. While coincident lidar data eluded us, we did expand our database allowing us to develop the first classification system to categorize mesospheric bore observations. We also verify for the first time that a mesospheric inversion layer would support bore formation as proposed. Some of the bore data exhibits features unexpected and new. Most intriguing is that the brightness relationship between airglow layers is reversed and accompanied by a lateral shift! This was the first such "inverse" event reported in the scientific community, and its seemingly contradictory nature fails to support the existing basic theory. Working with researchers at the Air Force Research Laboratory, we propose a new theory extending the original numerical model. We also compare the data to another non-linear theory and find both that: (1) neither theory explains all the observable features, and (2) each theory succeeds in explaining some characteristics not addressed by the competing theory. This theory development suggests that mesospheric bores likely are nonlinear structures propagating within upper atmospheric waveguides such as thermal-inversion layers or wind-shear ducts. Well into this thesis, we realized the critical and complicated role calibration plays in ensuring the condition of our data. Calibration reduces the discrepancies between the raw error-prone data and a true portrayal of the phenomena, facilitating the generation of congruent, accurate data for analysis. To address some of the calibration challenges and to alleviate some of the confusion for future graduate students, a portion of this dissertation is devoted to providing the first, comprehensive presentation of calibration -- detailing topics, techniques, methodologies, and results, as they pertain to airglow imagers.
Space Physics; Mesosphere; Bore; Gravity Wave; Airglow; Allsky Imager; Aeronomy; Space Weather; Ionosphere; Imager Calibration; Electrical and Computer Engineering
dissertation or thesis